diff options
Diffstat (limited to '75683-h')
| -rw-r--r-- | 75683-h/75683-h.htm | 12020 | ||||
| -rw-r--r-- | 75683-h/images/cover.jpg | bin | 0 -> 252587 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p012.jpg | bin | 0 -> 256360 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p016.jpg | bin | 0 -> 247981 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p017.jpg | bin | 0 -> 257243 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p023.jpg | bin | 0 -> 260472 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p028.jpg | bin | 0 -> 260684 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p032.jpg | bin | 0 -> 255935 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p040.jpg | bin | 0 -> 212555 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p041.jpg | bin | 0 -> 246492 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p041b.jpg | bin | 0 -> 245648 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p042.jpg | bin | 0 -> 215871 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p046.jpg | bin | 0 -> 189249 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p047.jpg | bin | 0 -> 255892 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p049.jpg | bin | 0 -> 155778 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p050.jpg | bin | 0 -> 254554 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p051.jpg | bin | 0 -> 254768 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p053.jpg | bin | 0 -> 255553 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p054.jpg | bin | 0 -> 136278 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p055.jpg | bin | 0 -> 215474 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p056.jpg | bin | 0 -> 241232 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p062.jpg | bin | 0 -> 254534 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p072.jpg | bin | 0 -> 216768 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p073.jpg | bin | 0 -> 255750 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p076.jpg | bin | 0 -> 254153 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p077.jpg | bin | 0 -> 257691 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p081.jpg | bin | 0 -> 256326 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p082.jpg | bin | 0 -> 260762 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p085.jpg | bin | 0 -> 247986 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p087.jpg | bin | 0 -> 176019 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p088.jpg | bin | 0 -> 234464 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p095.jpg | bin | 0 -> 203700 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p096.jpg | bin | 0 -> 164684 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p098.jpg | bin | 0 -> 150649 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p100.jpg | bin | 0 -> 251385 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p111.jpg | bin | 0 -> 231133 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p117.jpg | bin | 0 -> 253109 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p122.jpg | bin | 0 -> 248147 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p127.jpg | bin | 0 -> 178302 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p127b.jpg | bin | 0 -> 185751 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p188.jpg | bin | 0 -> 247867 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p190.jpg | bin | 0 -> 261021 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p192.jpg | bin | 0 -> 256533 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p193.jpg | bin | 0 -> 236682 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p197.jpg | bin | 0 -> 100444 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p197b.jpg | bin | 0 -> 258441 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p202.jpg | bin | 0 -> 243316 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p208.jpg | bin | 0 -> 194091 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p209.jpg | bin | 0 -> 243342 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p210.jpg | bin | 0 -> 186083 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p213.jpg | bin | 0 -> 244235 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p221.jpg | bin | 0 -> 261119 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p233.jpg | bin | 0 -> 248685 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p235.jpg | bin | 0 -> 132543 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p253.jpg | bin | 0 -> 254855 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p255.jpg | bin | 0 -> 259156 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p258.jpg | bin | 0 -> 257891 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p262.jpg | bin | 0 -> 258331 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p264.jpg | bin | 0 -> 131733 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p264r.jpg | bin | 0 -> 125201 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p277.jpg | bin | 0 -> 137212 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p278.jpg | bin | 0 -> 260433 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p282.jpg | bin | 0 -> 194859 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p283.jpg | bin | 0 -> 186097 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p286.jpg | bin | 0 -> 166966 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p288.jpg | bin | 0 -> 248579 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p291.jpg | bin | 0 -> 116977 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p314.jpg | bin | 0 -> 260382 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p316.jpg | bin | 0 -> 254153 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p318.jpg | bin | 0 -> 257734 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p323.jpg | bin | 0 -> 257063 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p325.jpg | bin | 0 -> 260208 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p330.jpg | bin | 0 -> 104582 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p332.jpg | bin | 0 -> 259445 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p345.jpg | bin | 0 -> 241499 bytes | |||
| -rw-r--r-- | 75683-h/images/i_p347.jpg | bin | 0 -> 168870 bytes |
76 files changed, 12020 insertions, 0 deletions
diff --git a/75683-h/75683-h.htm b/75683-h/75683-h.htm new file mode 100644 index 0000000..78152bc --- /dev/null +++ b/75683-h/75683-h.htm @@ -0,0 +1,12020 @@ +<!DOCTYPE html> +<html lang="en"> +<head> + <meta charset="UTF-8"> + <title> + The Telephone, Microphone, & Phonograph | Project Gutenberg + </title> + <link rel="icon" href="images/cover.jpg" type="image/x-cover"> + <style> /* <![CDATA[ */ + +body { + margin-left: 2.5em; + margin-right: 2.5em; +} +.x-ebookmaker body {margin: 0;} +.x-ebookmaker-drop {color: inherit;} + +h1, h2 { + text-align: center; + clear: both; + margin-top: 2.5em; + margin-bottom: 1em; + word-spacing: .2em; +} + +h1 {line-height: 1.5; font-weight: normal; font-size: 1.2em;} + +h2.chap {margin-bottom: 0;} +h2+p {margin-top: 1.5em;} +h2 .subhead {display: block; margin-top: 1em; margin-bottom: 1em;} +.x-ebookmaker h1, .x-ebookmaker .chapter, .x-ebookmaker .section {page-break-before: always;} +.x-ebookmaker h1.nobreak, .x-ebookmaker h2.nobreak, .x-ebookmaker .nobreak {page-break-before: avoid; padding-top: 0;} + +.transnote h2 { + margin-top: .5em; + margin-bottom: 1em; +} + +.subhead { + text-indent: 0; + text-align: center; + font-size: smaller; +} + +p { + text-indent: 1.75em; + margin-top: .51em; + margin-bottom: .24em; + text-align: justify; +} +.x-ebookmaker p { + margin-top: .5em; + margin-bottom: .25em; +} + +.caption p, .center p, p.center {text-align: center; text-indent: 0;} + +.p2 {margin-top: 2em;} +.p4 {margin-top: 4em;} +.vspace {line-height: 1.5;} + +.in0 {text-indent: 0;} + +.xsmall {font-size: 60%;} +.small {font-size: 70%;} +.smaller {font-size: 85%;} +.larger {font-size: 125%;} +.xxlarge {font-size: 200%;} + +.center {text-align: center;} + +.smcap {font-variant: small-caps;} +.allsmcap {font-variant: small-caps; text-transform: lowercase;} +.firstword {font-variant: small-caps;} + +hr { + width: 33%; + margin: 4em auto 4em auto; + clear: both; +} +.x-ebookmaker hr { + margin-top: .1em; + margin-bottom: .1em; + visibility: hidden; + color: white; + width: .01em; + display: none; +} +hr.narrow {width: 10em; margin: 1em auto 1em auto;} + +table { + margin-left: auto; + margin-right: auto; + max-width: 80%; + border-collapse: collapse; +} +.x-ebookmaker table {width: auto; max-width: 90%; margin: 1em auto 1em auto;} + +.tdl { + text-align: left; + vertical-align: top; + padding-right: 1em; + padding-left: 1.5em; + text-indent: -1.5em; +} +.x-ebookmaker .tdl { + padding-left: 1em; + text-indent: -1em; + padding-right: 0; +} + +.tdc {text-align: center;} +.tdc.chap, .tdl.chap { + font-size: 110%; + padding-top: 1.5em; + padding-bottom: .5em; +} + +.tdr { + text-align: right; + vertical-align: bottom; + padding-left: .3em; + white-space: nowrap; +} + +.pagenum { + position: absolute; + right: .25em; + text-indent: 0; + text-align: right; + font-size: 70%; + font-weight: normal; + font-variant: normal; + font-style: normal; + letter-spacing: normal; + line-height: normal; + color: #acacac; + border: .0625em solid #acacac; + background: #ffffff; + padding: .0625em .125em; +} + +.figcenter { + margin: 2em auto 2em auto; + text-align: center; + page-break-inside: avoid; +} + +.figleft { + float: left; + clear: left; + margin-left: 0; + margin-bottom: 1em; + margin-top: 1em; + margin-right: 1em; + padding: 0; + text-align: center; + min-width: 5%; + max-width: 50%; + page-break-inside: avoid; +} +.figright { + float: right; + clear: right; + margin-left: 1em; + margin-bottom: 1em; + margin-top: 1em; + margin-right: 0; + padding: 0; + text-align: center; + min-width: 5%; + max-width: 50%; + page-break-inside: avoid; +} +.x-ebookmaker-2 .figleft, .x-ebookmaker-2 .figright { + float: none; + clear: none; + margin: 1em auto 1em auto; + min-width: 0; + max-width: 100%; +} + +img { + padding: 1em 0 0 0; + max-width: 100%; + height: auto; +} + +.caption {text-align: center; margin-top: 0;} + +.footnotes { + border: thin dashed black; + margin: 4em 5% 1em 5%; + padding: .5em 1em .5em 1.5em; +} +.x-ebookmaker .footnotes {margin: 2em 0 1em 0;} + +.footnote {font-size: .95em;} +.footnote p {text-indent: 1em;} +.footnote p.in0 {text-indent: 0;} +.footnote p.fn1 {text-indent: -.7em;} +.footnote p.fn2 {text-indent: -1.1em;} + +.fnanchor, .footnote .label { + vertical-align: 60%; + line-height: .7; + font-size: smaller; + text-decoration: none; +} +.fnanchor {font-weight: bold; font-size: .8em;} +.footnote .label {font-size: .8em;} +h2 .fnanchor {font-size: .5em; vertical-align: text-top;} + +.transnote { + border: .3em double gray; + font-family: sans-serif, serif; + margin-left: 5%; + margin-right: 5%; + margin-top: 4em; + margin-bottom: 2em; + padding: 1em; +} +.x-ebookmaker .transnote { + page-break-before: always; + page-break-after: always; + margin-left: 2%; + margin-right: 2%; + margin-top: 1em; + margin-bottom: 1em; + padding: .5em; +} + +.wspace {word-spacing: .3em;} + +span.locked {white-space:nowrap;} +.pagenum br {display: none; visibility: hidden;} + + /* ]]> */ </style> +</head> + +<body> +<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 75683 ***</div> + +<div class="transnote section"> +<p class="center larger">Transcriber’s Note</p> + +<p>Larger versions of most illustrations may be seen by right-clicking them +and selecting an option to view them separately, or by double-tapping and/or +stretching them.</p> + +<p><a href="#Transcribers_Notes">Additional notes</a> will be found near the end of this ebook.</p> +<div> </div> +</div> + +<div class="section"> +<h1><span class="smaller">THE</span> <br>TELEPHONE, MICROPHONE, & PHONOGRAPH</h1> +<hr class="chap x-ebookmaker-drop"> +<div> </div> +</div> + +<div class="section center vspace wspace"> +<p class="xxlarge"> +THE TELEPHONE<br> +THE MICROPHONE & THE PHONOGRAPH</p> + +<p class="p2">BY<br> +<span class="larger">COUNT DU MONCEL</span><br> +<span class="small">MEMBRE DE L’INSTITUT</span></p> + +<p class="p2 smaller"><i>AUTHORISED TRANSLATION<br> +WITH ADDITIONS AND CORRECTIONS BY THE AUTHOR</i></p> + +<p class="p2">WITH 70 ILLUSTRATIONS ON WOOD</p> + +<p class="p2 larger"><i>FOURTH EDITION</i></p> + +<p class="p2"><span class="larger">LONDON</span><br> +KEGAN PAUL, TRENCH, TRÜBNER, & CO. <span class="smcap">Ltd.</span><br> +<span class="smaller">PATERNOSTER HOUSE, CHARING CROSS ROAD<br> +1892</span> +</p> +<hr class="chap x-ebookmaker-drop"> +</div> + +<div class="section p4 center"> +<p><span class="pagenum" id="Page_v">v</span></p> +<p>(<i>The rights of translation and of reproduction are reserved</i>)</p> +<div> </div> +</div> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="CONTENTS"><i>CONTENTS.</i></h2> +</div> + +<table id="toc"> +<tr class="xsmall"> + <td></td> + <td class="tdr">PAGE</td> +</tr> +<tr> + <td class="tdl">History of the telephone</td> + <td class="tdr"><a href="#Page_1">1</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_11">MUSICAL TELEPHONES</a>.</i></td> +</tr> +<tr> + <td class="tdl">Reiss’s telephone</td> + <td class="tdr"><a href="#Page_11">11</a></td> +</tr> +<tr> + <td class="tdl">Wray’s telephone</td> + <td class="tdr"><a href="#Page_15">15</a></td> +</tr> +<tr> + <td class="tdl">Electric harmonica</td> + <td class="tdr"><a href="#Page_18">18</a></td> +</tr> +<tr> + <td class="tdl">Gray’s telephone</td> + <td class="tdr"><a href="#Page_21">21</a></td> +</tr> +<tr> + <td class="tdl">Pollard and Garnier’s singing condenser</td> + <td class="tdr"><a href="#Page_26">26</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_30">SPEAKING TELEPHONES</a>.</i></td> +</tr> +<tr> + <td class="tdl">String telephones</td> + <td class="tdr"><a href="#Page_31">31</a></td> +</tr> +<tr> + <td class="tdl">Bell’s electric telephone</td> + <td class="tdr"><a href="#Page_35">35</a></td> +</tr> +<tr> + <td class="tdl">Gray’s share in invention of telephone</td> + <td class="tdr"><a href="#Page_62">62</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_67">FUNDAMENTAL PRINCIPLES OF BELL TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">Explanation of principles</td> + <td class="tdr"><a href="#Page_67">67</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_71">ORDINARY ARRANGEMENT OF BELL TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">Description and illustrations</td> + <td class="tdr"><a href="#Page_71">71</a><span class="pagenum" id="Page_vi">vi</span></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_83">BATTERY TELEPHONES</a>.</i></td> +</tr> +<tr> + <td class="tdl">Edison’s telephone</td> + <td class="tdr"><a href="#Page_83">83</a></td> +</tr> +<tr> + <td class="tdl">Edison’s chemical telephone</td> + <td class="tdr"><a href="#Page_90">90</a></td> +</tr> +<tr> + <td class="tdl">Navez’ telephone</td> + <td class="tdr"><a href="#Page_93">93</a></td> +</tr> +<tr> + <td class="tdl">Pollard and Garnier’s telephone</td> + <td class="tdr"><a href="#Page_97">97</a></td> +</tr> +<tr> + <td class="tdl">Hellesen’s telephone</td> + <td class="tdr"><a href="#Page_100">100</a></td> +</tr> +<tr> + <td class="tdl">Thomson and Houston’s telephone</td> + <td class="tdr"><a href="#Page_101">101</a></td> +</tr> +<tr> + <td class="tdl">Telephones with liquid senders</td> + <td class="tdr"><a href="#Page_103">103</a></td> +</tr> +<tr> + <td class="tdl">Telephones with voltaic arcs</td> + <td class="tdr"><a href="#Page_107">107</a></td> +</tr> +<tr> + <td class="tdl">Mercury telephones</td> + <td class="tdr"><a href="#Page_110">110</a></td> +</tr> +<tr> + <td class="tdl">Friction telephones</td> + <td class="tdr"><a href="#Page_113">113</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_114">MODIFICATION OF BELL TELEPHONES</a>.</i></td> +</tr> +<tr> + <td class="tdl">Telephones with several diaphragms</td> + <td class="tdr"><a href="#Page_114">114</a></td> +</tr> +<tr> + <td class="tdl">Gray’s system</td> + <td class="tdr"><a href="#Page_118">118</a></td> +</tr> +<tr> + <td class="tdl">Phelps’s system</td> + <td class="tdr"><a href="#Page_118">118</a></td> +</tr> +<tr> + <td class="tdl">Cox Walker’s system</td> + <td class="tdr"><a href="#Page_121">121</a></td> +</tr> +<tr> + <td class="tdl">Trouvé’s system</td> + <td class="tdr"><a href="#Page_121">121</a></td> +</tr> +<tr> + <td class="tdl">Demoget’s system</td> + <td class="tdr"><a href="#Page_124">124</a></td> +</tr> +<tr> + <td class="tdl">Mac Tighe’s system</td> + <td class="tdr"><a href="#Page_125">125</a></td> +</tr> +<tr> + <td class="tdl">Modifications of telephonic organs</td> + <td class="tdr"><a href="#Page_125">125</a></td> +</tr> +<tr> + <td class="tdl">Righi’s system</td> + <td class="tdr"><a href="#Page_126">126</a></td> +</tr> +<tr> + <td class="tdl">Ader’s system</td> + <td class="tdr"><a href="#Page_129">129</a></td> +</tr> +<tr> + <td class="tdl">Jorgenson’s system</td> + <td class="tdr"><a href="#Page_131">131</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_132">EXPERIMENTS WITH THE TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">On the effects of voltaic and induced currents</td> + <td class="tdr"><a href="#Page_132">132</a></td> +</tr> +<tr> + <td class="tdl">On the effects of different telephonic organs</td> + <td class="tdr"><a href="#Page_139">139</a></td> +</tr> +<tr> + <td class="tdl">Edison’s experiments</td> + <td class="tdr"><a href="#Page_140">140</a></td> +</tr> +<tr> + <td class="tdl">Canestrelli’s experiments</td> + <td class="tdr"><a href="#Page_142">142</a></td> +</tr> +<tr> + <td class="tdl">Hughes’s and Roy’s experiments</td> + <td class="tdr"><a href="#Page_143">143</a></td> +</tr> +<tr> + <td class="tdl">Bréguet’s experiments</td> + <td class="tdr"><a href="#Page_149">149</a><span class="pagenum" id="Page_vii">vii</span></td> +</tr> +<tr> + <td class="tdl">Luvini’s experiments</td> + <td class="tdr"><a href="#Page_149">149</a></td> +</tr> +<tr> + <td class="tdl">Warwick’s experiments</td> + <td class="tdr"><a href="#Page_151">151</a></td> +</tr> +<tr> + <td class="tdl">Experiments on the effects of mechanical shocks</td> + <td class="tdr"><a href="#Page_154">154</a></td> +</tr> +<tr> + <td class="tdl">Des Portes’ experiments</td> + <td class="tdr"><a href="#Page_154">154</a></td> +</tr> +<tr> + <td class="tdl">Thompson’s experiments</td> + <td class="tdr"><a href="#Page_158">158</a></td> +</tr> +<tr> + <td class="tdl">Theory of telephone</td> + <td class="tdr"><a href="#Page_159">159</a></td> +</tr> +<tr> + <td class="tdl">Nature of vibrations</td> + <td class="tdr"><a href="#Page_160">160</a></td> +</tr> +<tr> + <td class="tdl">Action of diaphragm</td> + <td class="tdr"><a href="#Page_163">163</a></td> +</tr> +<tr> + <td class="tdl">Action of magnet</td> + <td class="tdr"><a href="#Page_167">167</a></td> +</tr> +<tr> + <td class="tdl">Action of currents</td> + <td class="tdr"><a href="#Page_169">169</a></td> +</tr> +<tr> + <td class="tdl">Wiesendanger’s thermophone</td> + <td class="tdr"><a href="#Page_171">171</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_173">OTHER EXPERIMENTS WITH THE TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">D’Arsonval’s experiments</td> + <td class="tdr"><a href="#Page_173">173</a></td> +</tr> +<tr> + <td class="tdl">Eick’s experiments</td> + <td class="tdr"><a href="#Page_175">175</a></td> +</tr> +<tr> + <td class="tdl">Demoget’s experiments</td> + <td class="tdr"><a href="#Page_176">176</a></td> +</tr> +<tr> + <td class="tdl">Sensitiveness of telephone</td> + <td class="tdr"><a href="#Page_179">179</a></td> +</tr> +<tr> + <td class="tdl">Hellesen’s experiments</td> + <td class="tdr"><a href="#Page_180">180</a></td> +</tr> +<tr> + <td class="tdl">Zetsche’s experiments</td> + <td class="tdr"><a href="#Page_181">181</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_182">THE MICROPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">History of microphone</td> + <td class="tdr"><a href="#Page_182">182</a></td> +</tr> +<tr> + <td class="tdl">Different systems</td> + <td class="tdr"><a href="#Page_187">187</a></td> +</tr> +<tr> + <td class="tdl">Hughes’s microphone</td> + <td class="tdr"><a href="#Page_188">188</a></td> +</tr> +<tr> + <td class="tdl">Gaiffe’s system</td> + <td class="tdr"><a href="#Page_190">190</a></td> +</tr> +<tr> + <td class="tdl">Carette’s system</td> + <td class="tdr"><a href="#Page_191">191</a></td> +</tr> +<tr> + <td class="tdl">Ducretet’s system</td> + <td class="tdr"><a href="#Page_192">192</a></td> +</tr> +<tr> + <td class="tdl">Ducretet’s speaker</td> + <td class="tdr"><a href="#Page_193">193</a></td> +</tr> +<tr> + <td class="tdl">Boudet’s speaker</td> + <td class="tdr"><a href="#Page_195">195</a></td> +</tr> +<tr> + <td class="tdl">Gaiffe’s thermoscope</td> + <td class="tdr"><a href="#Page_197">197</a></td> +</tr> +<tr> + <td class="tdl">Blyth’s system</td> + <td class="tdr"><a href="#Page_199">199</a></td> +</tr> +<tr> + <td class="tdl">Microphone as a speaking instrument</td> + <td class="tdr"><a href="#Page_200">200</a></td> +</tr> +<tr> + <td class="tdl">Hughes’s system</td> + <td class="tdr"><a href="#Page_203">203</a></td> +</tr> +<tr> + <td class="tdl">Other arrangements of microphones</td> + <td class="tdr"><a href="#Page_205">205</a><span class="pagenum" id="Page_viii">viii</span></td> +</tr> +<tr> + <td class="tdl">Varcy’s and Trouvé’s microphones</td> + <td class="tdr"><a href="#Page_207">207</a></td> +</tr> +<tr> + <td class="tdl">Lippens’s microphone</td> + <td class="tdr"><a href="#Page_209">209</a></td> +</tr> +<tr> + <td class="tdl">Hughes’s experiments</td> + <td class="tdr"><a href="#Page_211">211</a></td> +</tr> +<tr> + <td class="tdl">Hughes’s theory</td> + <td class="tdr"><a href="#Page_215">215</a></td> +</tr> +<tr> + <td class="tdl">Microphone used as thermoscope</td> + <td class="tdr"><a href="#Page_217">217</a></td> +</tr> +<tr> + <td class="tdl">Edison’s thermoscope</td> + <td class="tdr"><a href="#Page_219">219</a></td> +</tr> +<tr> + <td class="tdl">Experiments in London</td> + <td class="tdr"><a href="#Page_220">220</a></td> +</tr> +<tr> + <td class="tdl">Experiment at Bellinzona</td> + <td class="tdr"><a href="#Page_223">223</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_225">APPLICATIONS OF MICROPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">Its application to scientific research</td> + <td class="tdr"><a href="#Page_226">226</a></td> +</tr> +<tr> + <td class="tdl">Application to telephonic relays</td> + <td class="tdr"><a href="#Page_229">229</a></td> +</tr> +<tr> + <td class="tdl">Application to surgery</td> + <td class="tdr"><a href="#Page_232">232</a></td> +</tr> +<tr> + <td class="tdl">Various applications</td> + <td class="tdr"><a href="#Page_236">236</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_238">EXTERNAL INFLUENCE ON TELEPHONIC TRANSMISSIONS</a>.</i></td> +</tr> +<tr> + <td class="tdl">Disturbing influences</td> + <td class="tdr"><a href="#Page_239">239</a></td> +</tr> +<tr> + <td class="tdl">Confusion of circuits</td> + <td class="tdr"><a href="#Page_241">241</a></td> +</tr> +<tr> + <td class="tdl">Induced reactions</td> + <td class="tdr"><a href="#Page_243">243</a></td> +</tr> +<tr> + <td class="tdl">Mr. Preece’s suggestions</td> + <td class="tdr"><a href="#Page_245">245</a></td> +</tr> +<tr> + <td class="tdl">Effects of heat and moisture</td> + <td class="tdr"><a href="#Page_249">249</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_251">ESTABLISHMENT OF TELEPHONE STATION</a>.</i></td> +</tr> +<tr> + <td class="tdl">Pollard and Garnier’s system</td> + <td class="tdr"><a href="#Page_252">252</a></td> +</tr> +<tr> + <td class="tdl">Bréguet and Roosevelt’s system</td> + <td class="tdr"><a href="#Page_254">254</a></td> +</tr> +<tr> + <td class="tdl">Edison’s system</td> + <td class="tdr"><a href="#Page_257">257</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_260">CALL-BELLS AND ALARUMS</a>.</i></td> +</tr> +<tr> + <td class="tdl">Weinhold’s system</td> + <td class="tdr"><a href="#Page_262">262</a></td> +</tr> +<tr> + <td class="tdl">Dutertre and Gouault’s system</td> + <td class="tdr"><a href="#Page_264">264</a><span class="pagenum" id="Page_ix">ix</span></td> +</tr> +<tr> + <td class="tdl">Puluj’s system</td> + <td class="tdr"><a href="#Page_266">266</a></td> +</tr> +<tr> + <td class="tdl">Chiddey’s system</td> + <td class="tdr"><a href="#Page_267">267</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_268">APPLICATIONS OF TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">Its application to simultaneous transmissions</td> + <td class="tdr"><a href="#Page_270">270</a></td> +</tr> +<tr> + <td class="tdl">Bell’s system</td> + <td class="tdr"><a href="#Page_273">273</a></td> +</tr> +<tr> + <td class="tdl">Lacour’s system</td> + <td class="tdr"><a href="#Page_276">276</a></td> +</tr> +<tr> + <td class="tdl">Gray’s system</td> + <td class="tdr"><a href="#Page_282">282</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_293">VARIOUS USES OF THE TELEPHONE</a>.</i></td> +</tr> +<tr> + <td class="tdl">Its use in offices</td> + <td class="tdr"><a href="#Page_293">293</a></td> +</tr> +<tr> + <td class="tdl">Its use in telegraphic service</td> + <td class="tdr"><a href="#Page_294">294</a></td> +</tr> +<tr> + <td class="tdl">Its application to military purposes</td> + <td class="tdr"><a href="#Page_297">297</a></td> +</tr> +<tr> + <td class="tdl">Its application to industry</td> + <td class="tdr"><a href="#Page_302">302</a></td> +</tr> +<tr> + <td class="tdl">Its application to scientific research</td> + <td class="tdr"><a href="#Page_303">303</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_307">THE PHONOGRAPH</a>.</i></td> +</tr> +<tr> + <td class="tdl">Edison’s patent</td> + <td class="tdr"><a href="#Page_309">309</a></td> +</tr> +<tr> + <td class="tdl">Description of phonograph</td> + <td class="tdr"><a href="#Page_313">313</a></td> +</tr> +<tr> + <td class="tdl">Several systems</td> + <td class="tdr"><a href="#Page_322">322</a></td> +</tr> +<tr> + <td class="tdl">Theory of phonograph</td> + <td class="tdr"><a href="#Page_327">327</a></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_333">USES OF PHONOGRAPH</a>.</i></td> +</tr> +<tr> + <td class="tdl">Account by Edison</td> + <td class="tdr"><a href="#Page_333">333</a></td> +</tr> +<tr> + <td class="tdl">Lainbrigot’s system</td> + <td class="tdr"><a href="#Page_339">339</a></td> +</tr> +<tr> + <td class="tdl chap"><i>FABER’S SPEAKING MACHINE</i></td> + <td class="tdr"><a href="#Page_341">341</a><span class="pagenum" id="Page_x">x</span></td> +</tr> +<tr> + <td class="tdc chap" colspan="2"><i><a href="#toclink_351">APPENDIX</a>.</i></td> +</tr> +<tr> + <td class="tdl">Perrodon’s system of telephonic alarum</td> + <td class="tdr"><a href="#Page_351">351</a></td> +</tr> +<tr> + <td class="tdl">Varey’s microphone speaker</td> + <td class="tdr"><a href="#Page_352">352</a></td> +</tr> +<tr> + <td class="tdl">Fitch’s microphone speaker</td> + <td class="tdr"><a href="#Page_353">353</a></td> +</tr> +<tr> + <td class="tdl">Theory of telephone</td> + <td class="tdr"><a href="#Page_353">353</a></td> +</tr> +<tr> + <td class="tdl">Pollard’s microphone</td> + <td class="tdr"><a href="#Page_356">356</a></td> +</tr> +<tr> + <td class="tdl">Ader’s electrophone</td> + <td class="tdr"><a href="#Page_357">357</a></td> +</tr> +<tr> + <td class="tdl">Gower’s new telephone</td> + <td class="tdr"><a href="#Page_358">358</a></td> +</tr> +<tr> + <td class="tdl">Transmission of speech by telephones without diaphragm</td> + <td class="tdr"><a href="#Page_360">360</a></td> +</tr> +</table> +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_1">1</span></p> + +<h2 class="nobreak" id="THE_TELEPHONE">THE TELEPHONE,<br> + +<span class="subhead"><i>&c.</i></span></h2> + +<hr class="narrow"> + +<h2 class="nobreak" id="HISTORY_OF_THE_TELEPHONE"><i>HISTORY OF THE TELEPHONE.</i></h2> +</div> + +<p class="in0"><span class="firstword">Strictly</span> speaking, the telephone is merely an +instrument adapted for the transmission of sound +to a distance, and this idea of transmitting sound +is as old as the world itself. The Greeks made +use of means which might effect it, and there is no +doubt that these means were sometimes used for +the pagan oracles. But such transmission of sound +was within somewhat narrow limits, and certainly +did not exceed those of a speaking-tube. Mr. +Preece considers that the earliest document in +which this transmission of sound to a distance is +distinctly formulated, dates from 1667: he refers +to a paper by one Robert Hooke, who writes to +this effect: ‘It is not impossible to hear a whisper +at a furlong’s distance, it having been already done; +and perhaps the nature of the thing would not make<span class="pagenum" id="Page_2">2</span> +it more impossible, though that furlong should be +ten times multiply’d. And though some famous +authors have affirm’d it impossible to hear through +the thinnest plate of Muscovy glass; yet I know a +way, by which ’tis easie enough to hear one speak +through a wall a yard thick. It has not yet been +thoroughly examin’d how far otacousticons may be +improv’d, nor what other wayes there may be of +quickning our hearing, or conveying sound through +other bodies than the air; for that is not the only +medium I can assure the reader, that I have, by the +help of a distended wire, propagated the sound to a +very considerable distance in an instant, or with as +seemingly quick a motion as that of light, at least +incomparably quicker than that which at the same +time was propagated through the air; and this not +only in a straight line or direct, but in one bended +in many angles.’</p> + +<p>This plan for the transmission of sound is the +principle of the string telephones which have attracted +attention for some years, and it remained +in the stage of simple experiment until 1819, when +Sir Charles Wheatstone applied it to his magic +lyre. In this instrument, sounds were transmitted +through a long strip of deal, with one end in connection +with a sounding board: one step more led +to the use of the membrane employed in string +telephones. It would be difficult to say with whom +this idea originated, since it is claimed, as if beyond +dispute, by several telephone-makers. If we may<span class="pagenum" id="Page_3">3</span> +believe some travellers, it has long been used in +Spain for the correspondence of lovers. However +this may be, it was not to be found among the +scientific appliances of some years ago, and it was +even supposed by many persons that the cord +consisted of an acoustic tube of slender diameter. +Although the instrument has become a child’s toy, +it has great scientific importance, for it proves that +vibrations capable of reproducing speech may be +extremely minute, since they can be mechanically +transmitted more than a hundred yards.</p> + +<p>From the telegraphic point of view, however, the +problem of transmitting sounds to a distance was +far from being solved in this way, and the idea of +applying electricity to this mode of transmission +naturally arose as soon as the wonderful effects of +electric telegraphy were observed, that is, in the +years subsequent to 1839. A surprising discovery +made in America by Mr. Page, in 1837, and afterwards +investigated by MM. Wertheim, De la Rive, +and others, must also have led up to it: for it was +observed that a magnetic bar could emit sounds +when rapidly magnetised and demagnetised, and +these sounds corresponded with the number of +currents which produced them. Again, the electric +vibrators devised by MM. Macaulay, Wagner, +Neef, etc., and adapted to produce musical sounds, +between 1847–1852, by MM. Froment and Pétrina, +showed that the problem of transmitting sounds +to a distance was not insoluble. Yet, up to 1854,<span class="pagenum" id="Page_4">4</span> +no one had ventured to admit the possibility +of transmitting speech by electricity, and when +M. Charles Bourseul published in that year a paper +on the electric transmission of speech, the idea +was regarded as a fanciful dream. I confess +that I myself thought it incredible, and when I +produced the paper in the first edition of my account +of the applications of electricity, published +in 1854, I felt bound to add that the scheme +seemed more than doubtful. Yet, as the paper +was thoughtfully written, I had no hesitation in +publishing it, affixing the signature of CH. B. +Events justified this daring idea, and although it +did not include the only principle which could lead +to the reproduction of articulate sounds, yet it was +the germ of the fertile invention which has made +the names of Graham Bell and Elisha Gray famous. +For this reason I will again quote M. Charles +Bourseul’s paper.</p> + +<p>‘After the telegraphic marvels which can reproduce +at a distance hand-writings, or even more +or less complicated drawings, it may appear impossible +to penetrate further into the region of the +marvellous. Yet we will try to advance a few +steps further. I have, for example, asked myself +whether speech itself may not be transmitted by +electricity—in a word, if what is spoken in Vienna +may not be heard in Paris. The thing is practicable +in this <span class="locked">way:—</span></p> + +<p>‘We know that sounds are made by vibrations,<span class="pagenum" id="Page_5">5</span> +and are adapted to the ear by the same vibrations +which are reproduced by the intervening medium. +But the intensity of the vibrations diminishes very +rapidly with the distance: so that it is, even with +the aid of speaking-tubes and trumpets, impossible +to exceed somewhat narrow limits. Suppose that +a man speaks near a moveable disk, sufficiently +flexible to lose none of the vibrations of the voice, +that this disk alternately makes and breaks the +currents from a battery: you may have at a +distance another disk, which will simultaneously +execute the same vibrations.</p> + +<p>‘It is true that the intensity of the sounds produced +will be variable at the point of departure, at +which the disk vibrates by means of the voice, and +constant at the point of arrival, where it vibrates by +means of electricity; but it has been shown that +this does not change the sounds. It is, moreover, +evident that the sounds will be reproduced at the +same pitch.</p> + +<p>‘The present state of acoustic science does not +permit us to declare <i lang="la">à priori</i> if this will be precisely +the case with syllables uttered by the human voice. +The mode in which these syllables are produced +has not yet been sufficiently investigated. It is +true that we know that some are uttered by the +teeth, others by the lips, and so on; but this is +all.</p> + +<p>‘However this may be, observe that the syllables +can only reproduce upon the sense of hearing the<span class="pagenum" id="Page_6">6</span> +vibrations of the intervening medium: reproduce +precisely these vibrations, and you will reproduce +precisely these syllables.</p> + +<p>‘It is, at all events, impossible in the present +condition of science to prove the impossibility of +transmitting sound by electricity. Everything +tends to show, on the contrary, that there is such +a possibility. When the application of electro-magnetism +to the transmission of messages was +first discussed, a man of great scientific attainments +treated the idea as utopian, and yet there is now +direct communication between London and Vienna +by means of a simple wire. Men declared it to be +impossible, but so it is.</p> + +<p>‘It need not be said that numerous applications +of the highest importance will immediately arise +from the transmission of speech by electricity. +Any one who is not deaf and dumb may use this +mode of transmission, which would require no apparatus, +except an electric battery, two vibrating +disks, and a wire. In many cases, as for example +in large establishments, orders might be transmitted +in this way, although transmission by +electricity will not be used while it is necessary to +go from letter to letter, and to make use of telegraphs +which require use and apprenticeship. +However this may be, it is certain that in a more +or less distant future, speech will be transmitted by +electricity. <em>I have made some experiments in this +direction</em>: they are delicate, and demand time and<span class="pagenum" id="Page_7">7</span> +patience, but <em>the approximations obtained</em> promise a +favourable result.’</p> + +<p>This description is certainly not full enough to +enable us to discern from it the arrangement +which would lead to the solution of the problem, +and if the vibrations of the disk at the receiving +station were to follow from making and breaking +the current at the sending-station, under the +influence of vibrations caused by the voice, they +would only produce musical, and not articulate +sounds. Yet the idea was magnificent, as Mr. +Preece said, even when he thought it impossible to +realise it. Besides, it is easy to see that M. Bourseul +himself was not deceived as to the difficulties +of the problem, as far as articulate sounds are +concerned, for he points out, as we have seen, the +difference existing between the simple vibrations +which produce musical sounds, and the complex +vibrations which cause articulate sounds; but, +as he justly said: ‘Reproduce at the one end of +the line the vibrations of air caused at the other, +and speech will be transmitted, however complex +the mechanism may be by which it is effected.’ +We shall presently see how the problem was solved, +and it is probable that some attempts had already +enabled M. Bourseul to anticipate the solution of +the question; but there is nothing in his paper to +show what were the means he proposed, so that +the discovery of the electric transmission of speech +cannot reasonably be ascribed to him, and we do<span class="pagenum" id="Page_8">8</span> +not understand why we should be reproached for +having at that time failed to appreciate the importance +of a discovery which seemed to be then +only within the range of fancy.</p> + +<p>It was not until 1876 that the problem of the +electric transmission of speech was finally solved, +and the discovery has lately given rise to an interesting +controversy as to priority between Mr. +Elisha Gray, of Chicago, and Mr. Graham Bell, on +which we must say a few words.</p> + +<p>As early as 1874 Mr. Elisha Gray was occupied +with a system of musical telephone, which he +wished to apply to manifold telegraphic transmissions, +and the investigations which he made, +in order to establish this system under the best +possible conditions, gave him a glimpse of the +possibility of transmitting articulate words by electricity. +While carrying on his experiments on the +telegraphic system, he arranged in fact, about the +15th January, 1876, a system of <em>speaking telephone</em>, +and he deposited the specification and drawings in +the American Patent Office, in the form of a +<i lang="la">caveat</i> or provisional specification. The deposit +was made on the 14th February, 1876: on the very +same day, Mr. Graham Bell also deposited, in the +American Patent Office, a request for a patent in +which he spoke of an instrument of the same kind, +but with special application to simultaneous telegraphic +transmissions by means of a telephonic +apparatus; and the few words which could, in this<span class="pagenum" id="Page_9">9</span> +specification, refer to a telephone with articulate +sounds, applied to an instrument which, by Mr. +Bell’s own admission, had not produced any satisfactory +results. In Mr. Gray’s <i lang="la">caveat</i>, on the +contrary, the application of the instrument to the +electric transmission of speech alone is indicated, +the description of the system is complete, and the +drawings which accompany it are so exact, that a +telephone made from them would work perfectly: +this was proved by Mr. Gray himself, when, some +time afterwards, he finished his instruments, which +differed in no respect from the one described in Mr. +Bell’s statement as worked by a battery. On these +grounds Mr. Elisha Gray would certainly have +obtained the patent, if the expiration of his <i lang="la">caveat</i> +had not been the result of an omission of form in +the Patent Office, which, as we know, decides the +priority of inventions in America. An action on the +ground of this omission has lately been brought +against Mr. Bell, in the Supreme Court of the +American Patent Office, to set aside the patent +granted to him. If Mr. Gray did not appeal before, +it was because he was then wholly occupied with +experiments on the system of harmonic telephone, +applied to telegraphic communication, and he had +no time to attend to the matter.</p> + +<p>However this may be, Mr. Bell did not begin +to give serious attention to the speaking telephone +until he had obtained his patent, and his efforts +were soon crowned with success: a few months<span class="pagenum" id="Page_10">10</span> +later, he exhibited his speaking telephone at +Philadelphia, which has from that time attracted so +much public attention, and which, when perfected +in a practical point of view, reached Europe in the +autumn of 1877 under the form we know.</p> + +<p>To complete this summary account of the +telephone, we ought to say that since its success +a good many claims of priority have arisen, as if +by enchantment. Mr. John Camack, of English +origin, has among others claimed the invention +of the telephone, not merely relying on the description +he gave of the instrument in 1865, but on the +drawings he executed; he even adds, that if he had +not lacked means for its construction, this would +have been the date of the discovery of the telephone. +A similar pretension has been put forward +by Mr. Dolbear, a fellow countryman of Mr. Bell, +of whose claim we shall speak presently.</p> + +<p>Signor Manzetti, of Aosta, says the same thing, +asserting that his telephonic invention was described +in several newspapers of 1865, among others in +‘Le Petit Journal,’ of Paris, on the 22nd November, +1865; ‘Il Diritto’ at Rome, 16th July, 1865; +‘L’Echo d’Italia,’ New York, 9th August, 1865; +‘L’Italia,’ Florence, 10th August, 1865; ‘La Comuna +d’Italia,’ Genoa, 1st December, 1865; ‘La +Verità,’ Novara, 4th January, 1866; ‘Il Commercio,’ +Genoa, 6th January, 1866. It is true that +no description of the system was given, and that the +journals in question only asserted that experiments<span class="pagenum" id="Page_11">11</span> +had been made, which proved that the practical solution +of the problem of transmitting speech by electricity +became possible by this system. At any rate +M. Charles Bourseul must still have the credit of the +priority of the idea, and, in our opinion, all claims +made after the fact only merit slight consideration.</p> + +<p>Before considering Bell’s telephone, and the +different modifications which have been applied to +it, it seems worth while, in order to make the +reader perfectly familiar with these kinds of instruments, +to study the electro-musical telephones +which preceded it, and especially that of M. Reiss, +which was made in 1860, and became the starting +point of all the others. We shall find that these +instruments have very important applications, and +that telegraphy will probably be one day much +advanced by their use.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="MUSICAL_TELEPHONES"><span id="toclink_11"></span>MUSICAL TELEPHONES.</h2> +</div> + +<p><i>Telephone of M. Reiss.</i>—This telephone is, as +far as the reproduction of sound is concerned, +based upon Mr. Page’s discoveries in 1837, and, as +regards electric transmission, it is based on the +vibrating membrane of which Mr. L. Scott made +use in his phonautograph, in 1855. This instrument +is composed, like telegraphic systems, of two +distinct parts, a sender and a receiver, as represented +in <a href="#il_1">fig. 1</a>.</p> + +<p><span class="pagenum" id="Page_12">12</span></p> + +<figure id="il_1" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p012.jpg" width="1016" height="889" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 1.</span> + </figcaption> +</figure> + +<p>The sender was virtually composed of a sounding +box <span class="allsmcap">K</span>, having on its upper surface a large +circular opening, across which a membrane was +stretched, and in its centre there was fitted a thin +disk of platinum <i>o</i>, above which a metallic point <i>c</i> +was fixed, and this, together with the disk, constituted +the contact-breaker. On one face of the +sounding-box <span class="allsmcap">K</span>, there was a sort of speaking-tube, +for the purpose of collecting the sound, and directing +it to the interior of the box, in order that it<span class="pagenum" id="Page_13">13</span> +might then react upon the membrane. Part of +the box <span class="allsmcap">K</span> is broken away in the plate, in order +that the different parts of which it is made may be +seen.</p> + +<p>The rods <i>a</i>, <i>c</i>, which support the platinum point +<i>b</i>, are in metallic contact with a Morse key <i>t</i>, +placed on the side of the box <span class="allsmcap">K</span>, and with an electro-magnet +<span class="allsmcap">A</span>, which belongs to a telegraphic system, +intended to exchange the signals required to start +the action of the two instruments at their respective +stations.</p> + +<p>The receiver consists of a sounding-box <span class="allsmcap">B</span>, on +which rest two supports <i>d</i>, <i>d</i>, bearing an iron rod +of the thickness of a knitting needle. An induction +coil of insulated wire <i>g</i> is wound round this rod, and +the whole is enclosed by the lid <span class="allsmcap">D</span>, which concentrates +the sound already increased by the sounding-box: +for this purpose the box is provided with +two openings below the coil.</p> + +<p>The circuit is completed through the primary +of this coil by the two terminals 3 and 4, and a +Morse key <i>t</i> is placed at the side of box <span class="allsmcap">B</span>, in order +to exchange signals.</p> + +<p>In order to work this system, the speaking +instrument should be placed before the opening +<span class="allsmcap">T</span>, and this instrument may be a flute, a violin, +or even the human voice. The vibrations of air +occasioned by these instruments cause the telephonic +membrane to vibrate in unison, and the +latter, rapidly moving the platinum disk <i>o</i> to and<span class="pagenum" id="Page_14">14</span> +from the point <i>b</i>, causes a series of breaks in the +current, which are repeated in the iron wire <i>d d</i>, +and transformed into metallic vibrations, of which +the number is equal to that of the sounds successively +produced.</p> + +<p>According to this mode of action, the possibility +of transmitting sounds with their relative value +becomes intelligible: but it is equally clear that +sounds thus transmitted will not have the <em>timbre</em> +of those which produce them, since the <em>timbre</em> is +independent of the number of vibrations, and it +must be added that the sounds produced by M. +Reiss’s instrument were as shrill as those of a +child’s penny trumpet, and by no means attractive. +The problem of transmitting musical sounds by +electricity was, however, really solved, and it can be +said with truth that an air or a melody could be +heard at any given distance.</p> + +<p>The invention of this telephone dates, as we +have seen, from 1860, and Professor Heisler speaks +of it in his treatise of technical physics, published +at Vienna in 1866; he even asserts, in the article +which he devotes to the subject, that although the +instrument was still in its infancy, it was capable +of transmitting vocal melodies, and not merely +musical sounds. The system was afterwards perfected +by M. Van der Weyde, who, after reading +the account published by M. Heisler, sought to +make the box of the sender more sonorous, and +to strengthen the sounds produced by the receiver.<span class="pagenum" id="Page_15">15</span> +He writes as follows in the ‘American Scientific +Journal:’</p> + +<p>‘In 1868, I caused two telephones to be made, +similar to those I have described, and I exhibited +them at a meeting of the Polytechnic Club of the +American Institute. The transmitted sounds were +produced at the farthest extremity of the Cooper +Institute, quite outside the hall in which the +audience sat: the receiver was placed on a table +in the hall itself. The vocal airs were faithfully +reproduced, but the sound was rather weak and +nasal. I then tried to improve the instrument, and +I first obtained stronger vibrations in the box <span class="allsmcap">K</span> +by causing reverberation from the sides of the +box, by means of hollow partitions. I next intensified +the sounds produced by the receiver, +by introducing several iron wires into the coil, +instead of one. These improvements were submitted +to the meeting of the American Association +for the Advancement of Science, which was held in +1869, and it was considered that the invention +contained the germ of a new method of telegraphic +transmission which might lead to important results.’ +This opinion was soon afterwards justified by the +discoveries of Bell and Elisha Gray.</p> + +<p><i>Messrs. Cecil and Leonard Wray’s Telephone.</i>—This +system, represented in <a href="#il_2">figs. 2</a> and <a href="#il_3">3</a>, is simply +an improvement on that of M. Reiss, with the +object of intensifying the effects produced. The +sender is provided with two membranes, instead<span class="pagenum" id="Page_16">16</span> +of one; and its receiver, instead of being formed of +a single iron wire covered with a magnetising +coil, is composed of two distinct coils <span class="allsmcap">H</span>, <span class="allsmcap">H′</span> (<a href="#il_2">fig. 2</a>), +placed in the same straight line, and within which +are two iron rods. These rods are fastened by one +of their ends to two copper disks <span class="allsmcap">A</span>, <span class="allsmcap">B</span>; these disks +are maintained in a fixed position by screws <span class="allsmcap">I</span>, <span class="allsmcap">I′</span>, +and the two other extremities of the rods, between +the coils, are opposite each other, not touching, +but divided by a very small interval. The instrument +is set upon a sounding-box, in which there is +a hole <span class="allsmcap">T</span> in the space corresponding to the interval +between the coils: these coils communicate with +four terminals, which are connected with the electric +current in such a way that the adjacent poles of +the two rods are of opposite polarity, thus forming +a single magnet, divided in the centre. It seems +that by this arrangement the sound produced becomes +much more distinct.</p> + +<figure id="il_2" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p016.jpg" width="765" height="377" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 2.</span> + </figcaption> +</figure> + +<figure id="il_3" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p017.jpg" width="904" height="779" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 3.</span> + </figcaption> +</figure> + +<p>The form of the sender also is somewhat<span class="pagenum" id="Page_17">17</span> +different from the one we have previously described: +the upper part, instead of being horizontal, is rather +inclined, as it appears in <a href="#il_3">fig. 3</a>, and the opening <span class="allsmcap">E</span> +through which the sound has to communicate with +the vibrating membrane, occupies a great part of +the upper surface of the box, which consequently +appears to be somewhat oblique. The second +membrane <span class="allsmcap">G</span>, which is of caoutchouc, forms a sort +of partition which divides the box in two, starting +from the upper end of the opening: the inventor +states that this will protect the outer membrane <span class="allsmcap">D</span> +from the breath and other injurious effects, while +increasing the force of the vibrations produced on<span class="pagenum" id="Page_18">18</span> +the first membrane, as in a drum. The contact-breaker +itself also differs from the one in M. Reiss’s +instrument. The platinum disk <i>b</i> is only placed +in circuit by means of two slender wires of platinum +or steel, which are immersed in two small cups, +filled with mercury, and connected with the circuit. +In this way, the movements of the membrane <span class="allsmcap">D</span> +are free, and its vibration is rendered more easy.</p> + +<p>The circuit is also broken by a little platinum +point resting on a lever with a spring-joint, <span class="allsmcap">K H</span>, +which is above the disk: one end of the lever, +which is fixed below a kind of Morse key <span class="allsmcap">M I</span>, +makes it possible to close the circuit with the +hand, so as to give the signal for setting the +apparatus to work.</p> + +<p><i>Electric Harmonica.</i>—Long before M. Reiss’s +invention, and consequently still longer before that +of Mr. Elisha Gray, I mentioned a sort of electric +harmonica, and described it as follows in the first +edition of my ‘Exposé des applications de l’Electricité,’ +published in <span class="locked">1853:—</span></p> + +<p>‘The power possessed by electricity to set +metallic plates in motion and cause their vibration +has been used for the production of distinct sounds, +which can be combined and harmonised; but in +addition to this purely physical application, electro-magnetism +has come to the aid of certain instruments, +such as pianos, organs, &c., rendering +them capable of being played at a distance. So +that this extraordinary force may be turned to<span class="pagenum" id="Page_19">19</span> +account in arts which are apparently the least susceptible +of any application of electricity.</p> + +<p>‘We have already spoken of M. de la Rive’s +contact-breaker. It is, as we know, an iron disk, +soldered to a steel spring, and maintained in a +fixed position opposite to an electro-magnet by +another spring in connection with one branch of +the current. As the other branch, after passing +into the wire of the electro-magnet, terminates +in the iron disk itself, the electro-magnet is only +active at the moment when the disk touches the +terminal spring; at the moment of leaving it, the +magnetism ceases, and the iron disk returns to its +normal position, and then leaves it again. In this +way a vibration is produced, rapid in proportion +to the small size of the vibrating disk, and to the +greatness of the force produced by the approach of +the disk to the electro-magnet.</p> + +<p>‘In order to increase the acuteness of the +sounds, one or other of these expedients must be +employed. The simplest way is to use a screw +which can be tightened or relaxed at pleasure, +and which in this manner removes the vibrating disk +to a greater or less distance from the electro-magnet. +This is the case in M. Froment’s instrument, and +by this means he has obtained sounds of extraordinary +acuteness, although not unpleasant to +the ear.</p> + +<p>‘M. Froment has not applied the apparatus to +a musical instrument, but it is evident that it would<span class="pagenum" id="Page_20">20</span> +be easy to do so; it would only be necessary to +make the notes of a key-board act on metallic +levers, of a length corresponding to the position +required by the disk for the vibration of different +tones. These different levers, resting on the disk, +would act as a point of contact, but the point +would vary in position, according to the touch.</p> + +<p>‘If the current were constant, such an instrument +would certainly have many advantages over +the pipe instruments which are in use, since the +vibration might be prolonged at will in the case of +each note, and the sounds would be softer; unfortunately +the irregular action of the battery +makes it difficult in practice. These kinds of +instruments are therefore only used as a means of +regulating by ear the force of the battery, a much +more convenient regulator than the rheometers, +since it is possible to estimate by them the variations +of the battery during an experiment without +any distraction of the mind.’</p> + +<p>In 1856 M. Pétrina, of Prague, invented an +analogous arrangement, to which he gave the name +of electric harmonica, although, strictly speaking, he +had not thought of it as a musical instrument. This +is what I have said on the subject in vol. iv. of the +second edition of my ‘Exposé des applications de +l’Electricité,’ published in <span class="locked">1859:—</span></p> + +<p>‘The principle of this instrument is similar to +that of Neef’s rheotome, in which the hammer is +replaced by slender rods, whose vibrations produce<span class="pagenum" id="Page_21">21</span> +a sound. Four of these rods are placed side by +side, and when moved by keys, and arrested by +levers, produce combined sounds of which the origin +may be easily shown.’</p> + +<p>It is true that nothing is said in this passage +of the capability possessed by these instruments +of being played at a distance; but this idea was +quite legitimate, and German periodicals assert +that it was accomplished by M. Pétrina even before +1856. It was the result of what I said at the outset: +‘that electro-magnetism may come to the aid of +certain instruments, such as pianos, organs, &c., +<em>in order to enable them to be played at a distance</em>,’ and +I also pointed out the expedients employed for the +purpose, and even for setting them at work, under +the influence of a small musical box. I did not, +however, ascribe importance to the matter, and it is +only by way of historical illustration that I speak +of these systems.</p> + +<p><i>Telephone by Mr. Elisha Gray, of Chicago.</i>—This +system, invented in 1874, is in reality only an instrument +of the nature of those which preceded it, but +with important modifications, which made it possible +to apply it usefully to telegraphy. In an early +model, he made use of an induction coil, with +two helices, one over the other: the contact-breaker, +which was vibrating, was multiple, and so arranged +as to produce vibrations numerous enough to emit +sounds. These sounds may, as we have seen, be +modified by this arrangement, according to the<span class="pagenum" id="Page_22">22</span> +mode in which the instrument is adjusted, and if +there are a certain number of such contact-breakers +side by side, with vibrating disks so ordered as to +produce the different notes of the scale on several +octaves, it becomes possible, by a combination of +certain notes, to execute on this new kind of instrument +a piece of music such as may be produced +by an harmonium, an accordion, or any other instrument +with blowers. The contact-breakers are set +in motion by means of the primary current of +the induction coil, as it circulates through one or +other of the electro-magnets of these contact-breakers, +actuated by the lowering of the notes of +a key-board connected with them, and the secondary +currents which arise in the coil, in consequence +of the interruptions in the primary currents, +transmit the corresponding vibrations to a remote +receiver. There is an analogy between this instrument +and the telephones of which we have already +spoken by Reiss and Wray, but the effect is increased +by Mr. Gray’s modifications.</p> + +<p>We represent in <a href="#il_4">fig. 4</a> the arrangement of the +first system. The vibrators are <span class="allsmcap">A</span> and <span class="allsmcap">A′</span>, the +key-board <span class="allsmcap">M</span> and <span class="allsmcap">M′</span>, the induction coil <span class="allsmcap">B</span>, and +the receiver <span class="allsmcap">C</span>. This receiver consists, as we +see, of a simple electro-magnet <span class="allsmcap">N N′</span>: above its +poles there is a metal cylindrical case <span class="allsmcap">C</span>, of which +the bottom is made of iron, to serve as an armature. +This box, like a violin, is pierced with +two holes in the form <span class="allsmcap">S</span>, to serve as a sounding-board;<span class="pagenum" id="Page_23">23</span> +and Mr. Elisha Gray has ascertained that +the molecular motion which takes place in the +magnetic core and its armature, under the influence +of alternate magnetisation and demagnetisation, +sufficed to produce vibrations corresponding +to the velocity of these alternations, and to emit +sounds which became audible when they were magnified +by the sounding-board.</p> + +<figure id="il_4" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p023.jpg" width="891" height="862" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 4.</span> + </figcaption> +</figure> + +<p>It is quite intelligible that the effect obtained +in this system might be reproduced, if, instead of +contact-breakers or electric rheotomes, mechanical<span class="pagenum" id="Page_24">24</span> +contact-breakers were used at the sending station, +so arranged as to furnish the requisite number +of breaks in the current which communicates the +vibrations of the different notes of the scale. In +this way also it would be possible to dispense +with the induction coil, by causing the current +which has been broken by the mechanical contact-breaker +to react upon the receiver. Mr. Elisha +Gray has moreover made a different arrangement +of this telephonic system, which he has applied to +telegraphy for simultaneous electric transmissions, +of which we shall speak presently.</p> + +<p>If we may believe Mr. Elisha Gray, the vibrations +transmitted by the secondary currents would +be capable, by the intervention of the human body, +of causing the sounds to be reproduced at a distance +by conducting disks, which vibrate readily, and are +placed on a sounding-box. In this way musical +sounds may be evoked from copper cylinders placed +upon a table, from a metallic disk fastened to a kind +of violin, from a membrane stretched on a drum, or +from any other resonant substance, by touching any +of these objects with one hand, while holding the +end of the line with the other. These sounds, +of which the quality must vary with the substance +touched, would reproduce the transmitted note with +the precise number of vibrations which belong to it.<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">1</a></p> + +<p><span class="pagenum" id="Page_25">25</span></p> + +<p><i>Mr. Varley’s Telephone.</i>—This is, strictly speaking, +merely a musical telephone of the same kind +as that of Mr. Gray, but the arrangement of the +receiver is original and interesting. This part of +the instrument essentially consists of a drum of +large size (three or four feet in diameter), within +which is a condenser formed of four sheets of tinfoil, +divided by sheets of some insulating material, +and with a surface of about half the size of the +drum. The plates of the condenser are placed +parallel to the membranes of the drum, and very +little removed from its surface.</p> + +<p>If an electric charge is communicated to one of +the series of conducting plates of the condenser, +those which correspond to it are attracted, and if +they were movable they might communicate to +the intervening strata of air a movement which, on +reaching the membranes of the drum, might, by a +series of charges in rapid succession, cause the +membranes to vibrate, and thus produce sounds: +these sounds would correspond to the number of<span class="pagenum" id="Page_26">26</span> +charges and discharges which had occurred. Since +these charges and discharges are determined by the +contact of the two plates of the condenser, at the +extremities of the secondary circuit of an induction +coil, of which the primary circuit has been duly +broken, it becomes evident that, in order to cause +the drum to emit any given sound, it will be enough +to produce the number of vibrations in the contact-breaker +of the induction coil which are required for +this sound.</p> + +<p>The means employed by Mr. Varley to produce +these interruptions are the same which are in use +in several electrical instruments, and especially in +chronographs—an electro-magnetic tuning-fork, regulated +so as to emit the sound required. This +tuning-fork may, by acting as contact-breaker, react +on the primary current of the induction coil; if the +number of the tuning-forks equals that of the musical +notes which are to be transmitted, and if the electro-magnets +which set them in motion are connected +with the key-board of a piano, it would be possible +to transmit a melody to a distance by this system, +as well as by that of Mr. Elisha Gray.</p> + +<p>The peculiarity of this system consists in the +reproduction of sounds by the action of a condenser, +and we shall presently see that this idea, adopted +by Messrs. Pollard and Gamier, led to interesting +results.</p> + +<p><i>Singing Condenser of MM. Pollard and Garnier.</i>—This +instrument, which astonishes all who<span class="pagenum" id="Page_27">27</span> +hear it, attracted public attention in London some +time ago. It is difficult to say why its fame was +not greater, since much attention has been bestowed +on less curious instruments. It is a fact that we +have been able, thanks to MM. Pollard and Garnier, +to hear songs issue from a sort of copy-book, so as +to become audible throughout the room. The +songs thus reproduced are certainly not always +perfectly true; yet when the person who sings into +the sender is a musician, and understands how +to make use of it, the condenser in question will +emit sounds somewhat resembling those of the +violoncello or the hautbois.</p> + +<p>The singing instrument consists of a condenser +<span class="allsmcap">K</span>, formed of thirty sheets of paper, laid one over +the other, from nine to thirteen centimètres in +thickness: between these, twenty-eight sheets of +tinfoil, from six to twelve centimètres thick, are +intercalated, so joined as to form the two plates +of the condenser. For this purpose the pair sheets +are joined together at one end of the copy-book, +and the odd sheets at the other end. This system +is fastened to a stiff <em>carton</em>, after taking care to bind +it with a strip of paper, and the sheets of tinfoil +are joined to the two ends of the condenser by two +copper rims <span class="allsmcap">D</span>, <span class="allsmcap">D</span>, which are provided with terminals +for the circuit wire, and in this way the singing +instrument is constructed. A somewhat heavy +weight, placed upon the condenser to compress the +sheets, does not in any way prevent it from working;<span class="pagenum" id="Page_28">28</span> +and this vitiates the theory first put forward +to explain its effects, that the sheets were moved +by attraction.</p> + +<figure id="il_5" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p028.jpg" width="865" height="1079" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 5.</span> + </figcaption> +</figure> + +<p>The sending instrument consists of a sort +of telephone without a handle, <span class="allsmcap">E</span>, of which the +vibrating disk is formed of a very thin plate of tin. +A cylindrical piece of carbon <span class="allsmcap">C</span> is fastened to its +centre, and is supported by another cylinder of the<span class="pagenum" id="Page_29">29</span> +same material <span class="allsmcap">H</span>. This rests on a transverse piece +of wood <span class="allsmcap">A B</span>, jointed on the side <span class="allsmcap">A</span>, on the edge +opposite to the box, by means of a regulating screw +<span class="allsmcap">V</span>. An arched spring <span class="allsmcap">R</span> (the end of a watch spring) +placed across this piece of wood gives it a certain +elasticity beneath the pressure, and this elasticity is +necessary in order that the instrument may act +properly, and it thus becomes a sort of microphone +with a diaphragm.</p> + +<p>The tin plate is put into communication with +one pole of a battery <span class="allsmcap">P</span>, of six Leclanché cells, and +the lower carbon cylinder <span class="allsmcap">H</span> corresponds to the +primary helix of an induction coil <span class="allsmcap">M</span>, previously +connected with the second pole of the battery: +Finally, the two extremities of the secondary helix +of the coil, <i>a</i> and <i>b</i>, are in immediate connection +with the two plates <span class="allsmcap">D</span>, <span class="allsmcap">D</span>, of the condenser.</p> + +<p>This secondary helix should consist of twenty +strands of wire No. 32, covered with silk, and the +primary helix is made of five strands of wire No. +16. The length of the coil should not exceed +seven centimètres and the diameter of the core of +fine iron wire ought to be about one centimètre.</p> + +<p>In order to produce song on the condenser, +the sender must be so regulated that the two +carbons <span class="allsmcap">C</span> and <span class="allsmcap">H</span> do not touch each other in their +normal condition, but they should be so close that +in singing the vibrations of the disk <span class="allsmcap">L L</span> may effect +the needful contacts. The adjustment can be easily +made by the touch, and by uttering the same note<span class="pagenum" id="Page_30">30</span> +until it is repeated by the condenser. If three +notes, given in succession, are faithfully reproduced, +the instrument may be assumed to be properly +regulated, and, in order to make it work, it is enough +to apply the mouth to the mouthpiece as it is +applied to a reed pipe.</p> + +<p>In order to obtain a satisfactory result, the disk +of the instrument must be heard to vibrate, as in a +<i lang="fr">flûte à l’oignon</i>. Instead of carbons, contacts of +platinum may be used; but when arranged as we +have described, the instrument may be employed +for several purposes, as we shall see presently. +This instrument is made by MM. Chardin and +Prayer. M. Janssens has made the system more +portable by fastening the sender, represented in +<a href="#il_5">fig. 5</a>, to a handle in which the induction coil is +placed: the instrument then resembles an ordinary +telephone, and the vibration of the diaphragm is +made more easy by piercing two holes in it. On +the side of the sending-box, above and below the +diaphragm, there are binding screws in connection +with the end of the handle, since the instrument +may be used as an ordinary telephonic sender, and +even as a telephonic receiver.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="SPEAKING_TELEPHONES"><span id="toclink_30"></span>SPEAKING TELEPHONES.</h2> +</div> + +<p>We have seen that the telephones just described +can only transmit musical sounds, since they can +merely repeat simple vibrations, in greater or less<span class="pagenum" id="Page_31">31</span> +number, it is true, but not in simultaneous combinations +like those which reproduce articulate sounds. +Up to the time of Mr. Bell’s invention, the transmission +of speech could only take place with the aid of +acoustic tubes, or of the string telephones of which +we have spoken. Although these instruments have +no connection with the object of our study in this +work, we have thought it necessary to say a few +words about them, since they may sometimes be +combined with electric telephones, and also represent +the first stage of the invention.</p> + +<p><i>String Telephones.</i>—These instruments, which +have flooded the cities of Europe for several years, +since the date of the invention was 1867, are interesting +in themselves, and we are surprised that they +have not hitherto taken a place in the collections of +physical science. They are made of two metal or +cardboard tubes, in the form of a cylindrical cone: +one end is closed by a tightly stretched membrane +of parchment, in the centre of which the cord or +string intended to connect the two cylinders is +fastened by a knot. When two such tubes are connected +in this way, and the cord is tightly stretched, +as in <a href="#il_6">fig. 6</a>, it is only necessary to apply one tube +to the ear, while another speaks into the opening +of the other tube: the words spoken by the latter +are instantly transmitted, and it is even possible to +converse in quite an undertone. Under these conditions +the vibrations of the membrane affected by +the voice are mechanically transmitted to the other<span class="pagenum" id="Page_32">32</span> +membrane by the string, which, as Robert Hooke +declared in 1667, is a better transmitter of sound +than the air. In this way it is possible to communicate +at a distance of 170 yards, and the size and +nature of the cord have some influence. The sellers +of these instruments say that the best results are +obtained from silken cords, and the worst from +those made of hemp. Cords of plaited cotton are +usually employed for the sake of cheapness.</p> + +<figure id="il_6" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p032.jpg" width="887" height="729" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 6.</span> + </figcaption> +</figure> + +<p>In some patterns, the tubes are so arranged as +to present, between the membrane and the mouth, +a diaphragm pierced with a hole, and the instrument +somewhat resembles a bell with its base bored and<span class="pagenum" id="Page_33">33</span> +closed again a little above the parchment membrane; +but I have not observed that this pattern +is decidedly superior to the others.</p> + +<p>It has also been asserted that horn-shaped tubes +of nickel silver are to be preferred, of which I am +equally doubtful. At any rate, these instruments +have produced unexpected results; and although +their practical use is very limited, they are interesting +from a scientific point of view, and are +instructive toys for children.</p> + +<p>Mr. Millar, of Glasgow, declares that the effect +produced by these telephones depends very much +on the nature of the string, the way in which it is +attached, and the way in which the membrane is +fastened to the mouthpiece.</p> + +<p><i>Improvements made in the String Telephone.</i>—The +amazing effects of the Bell telephones have lately +brought the string telephones, which were only regarded +as children’s toys, again into fashion. Since +they have made it possible to transmit to several +persons the words reproduced by an electric telephone, +means have been sought for combining +them usefully with the latter, and the best mode of +making them speak on a string presenting several +angles has been sought for: it has been shown that, +under the usual conditions, these instruments only +speak distinctly when the string is stretched in +a right line. To solve this problem, it occurred +to M. A. Bréguet to make use of a sort of tambourine +for the supports, with the string passed<span class="pagenum" id="Page_34">34</span> +through their centre; the sound conveyed by that +part of the string which is in connection with the +speaking-horn causes the membrane of the tambourine +to vibrate, which again communicates the +vibration to the next portion of string. In this +way the angles may be multiplied at will, and the +string may be supported throughout the length compatible +with this kind of telephone, which does not +exceed 112 yards.</p> + +<p>M. A. Bréguet has also invented a system of relays +to accomplish the same object. He makes the +strings terminate in two membranes which close +the two openings of a brass cylinder. The sounds +reproduced on one of these membranes react +upon the other, which vibrates under its influence, +as if it were affected by the voice. The cylinder +then acts as an ordinary acoustic tube, and its form +may be varied at pleasure.</p> + +<p>M. A. Badet, on February 1, 1878, succeeded +in making string telephones in an analogous +way, and he used parchment stretched upon +frames which acted as resonant boards. The string +was fixed in the centre of the membrane, and made +with it the angle desired.</p> + +<p>Several scientific men, among others Messrs. +Wheatstone, Cornu, and Mercadier, have long been +occupied about these ways of transmission by wire, +and Messrs. Millar, Heaviside, and Nixon have +lately made some interesting experiments, on +which we must say a few words. Mr. Millar<span class="pagenum" id="Page_35">35</span> +ascertained that by means of a telegraphic wire, +stretched and connected by two copper wires with +two vibrating disks, musical sounds might be +conveyed to a distance exceeding 160 yards, and +that by stretching these wires through a house, +and connecting them with mouth-and-ear holes in +different rooms, communication between them +became perfectly easy.</p> + +<p>For the vibrating disks he employed wood, +metal, or gutta-percha, in the form of a drum, with +wires fixed in the centre. The sound seems to +become more intense in proportion to the thickness +of the wire.</p> + +<p>Messrs. Heaviside and Nixon, in their experiments +at Newcastle-on-Tyne, have ascertained that +the most effective wire was No. 4 of the English +gauge. They employed wooden disks ⅛ inch in +thickness, and these may be placed in any part of the +length of the wire. When the wire was well stretched +and motionless, it was possible to hear what was +said at a distance of 230 yards, and it seems that +Mr. Huntley, by using very thin iron diaphragms, +and by insulating the line wire on glass supports, +was able to transmit speech for 2,450 feet, in spite +of the zigzags made by the line on its supports.</p> + +<p><i>Mr. Graham Bell’s Electric Telephone.</i>—Telephonic +instruments were at this stage when Bell’s telephone +was shown at the Philadelphia Exhibition of +1876. Sir William Thompson did not hesitate to +call it ‘the wonder of wonders,’ and it instantly<span class="pagenum" id="Page_36">36</span> +attracted universal attention, although there was at +first much incredulity as to its genuineness. This +telephone, in fact, reproduced articulate words, a +result which surpassed all the conceptions of physicists. +In this case it was no longer a conception, +to be treated as visionary until there was proof to +the contrary: the instrument spoke, and even +spoke so loudly that it was not necessary to apply +the ear. Sir William Thompson spoke to this effect +on the subject at the meeting of the British Association +at Glasgow in September <span class="locked">1876:—</span></p> + +<p>‘In the department of telegraphs in the United +States I saw and heard Mr. Elisha Gray’s electric +telephone, of wonderful construction, which can +repeat four despatches at the same time in the +Morse code, and, with some improvements in +detail, this instrument is evidently capable of a +fourfold delivery. In the Canadian department +I heard “To be or not to be? There’s the rub,” +uttered through a telegraphic wire, and its pronunciation +by electricity only made the rallying tone of +the monosyllables more emphatic. The wire also repeated +some extracts from New York papers. With +my own ears I heard all this, distinctly articulated +through the slender circular disk formed by the +armature of an electro-magnet. It was my fellow-juryman, +Professor Watson, who, at the other +extremity of the line, uttered these words in a +loud and distinct voice, while applying his mouth +to a tightly stretched membrane provided with a<span class="pagenum" id="Page_37">37</span> +small piece of soft iron, which executed movements +corresponding to the sound vibrations of the air +close to an electro-magnet introduced into the +circuit. This discovery, the wonder of wonders +in electric telegraphy, is due to a young fellow-countryman +of our own, Mr. Graham Bell, a +native of Edinburgh and now naturalised in New +York.</p> + +<p>‘It is impossible not to admire the daring invention +by which we have been able to realise with +these simple expedients the complex problem of +reproducing by electricity the tones and delicate +articulations of voice and speech; and it was +necessary, in order to obtain this result, to find out +the means of varying the intensity of the current in +the same proportion as the inflections of the sound +emitted by the voice.’</p> + +<p>If we are to believe Mr. Graham Bell, the invention +of the telephone was not due to a spontaneous +and fortunate conception: it was the result of +his long and patient studies in acoustic science, and +of the labours of the physicists who preceded him.<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">2</a> +His father, Mr. Alexander Melville Bell, of Edinburgh, +had studied this science deeply, and had +even succeeded in representing with great ingenuity<span class="pagenum" id="Page_38">38</span> +the adaptation of the vocal organs for the +emission of sound. It was natural that he should +instil a taste for his favourite studies into his son’s +mind, and they made together numerous researches +in order to discover the relations which +exist between the different elements of speech in +different languages, and the musical relations of +vowels. It is true that several of these researches +had been made by M. Helmholtz, and under +more favourable conditions; but these studies +were of great use to Mr. Bell when he was afterwards +occupied with the telephone, and Helmholtz’s +experiments, which he repeated with one of +his friends, Mr. Hellis of London, concerning the +artificial reproduction of vowels by means of +electric tuning-forks, launched him into the study of +the application of electricity to acoustic instruments. +He first invented a system of an electric +harmonica with a key-board, in which the different +sounds of the scale were reproduced by electric +diapasons of different forms, adapted to different +notes, and which, when set in motion by the successive +lowering of the keys, could reproduce +sounds corresponding to the notes touched, just as +in an ordinary piano.</p> + +<p>He next, as he tells us, turned his attention to +telegraphy, and thought of making the Morse +telegraphs audible by causing the electro-magnetic +organ to react on sounding contacts. It is true +that this result had already been obtained in the<span class="pagenum" id="Page_39">39</span> +sounders used in telegraphy, but he thought that +by applying this system to his electric harmonica, +and by employing such an intensifying instrument +as Helmholtz’s resonator at the receiving station, +it would be possible to obtain through a single +wire simultaneous transmissions which should be +due to the action of the voice. We shall see +presently that this idea was realised almost at the +same time by several inventors, among others by +M. Paul Lacour, of Copenhagen, Mr. Elisha Gray, +of Chicago, and Messrs. Edison and Varley.</p> + +<p>Mr. Bell’s study of electric telephones really +dates from this time, and he passed from complex +to simple instruments, making a careful study of +the different modes of vibration which arise from +different modes of electric action. The following is an +abstract, with the omission of more technical details, +of the paper read by Mr. Bell to the Society of +Telegraphic Engineers, London, October 31, 1877.</p> + +<p>If the intensity of an electric current is represented +by the ordinates of a curve, and the duration +of breaks in the current by the abscissæ, the +given curve may represent the waves of the positive +or negative current respectively, above and below +the line of <span class="allsmcap">X</span>, and these waves will be more or less +accentuated, just as the transmitted currents are +more or less instantaneous.</p> + +<p>If the currents which are interrupted to produce +a sound are quite instantaneous in their manifestation, +the curve represents a series of isolated indentations,<span class="pagenum" id="Page_40">40</span> +as we see in <a href="#il_7">fig. 7</a>; and if the interruptions +are so made as only to produce differences of +intensity, the curve is presented under the form of +<a href="#il_8">fig. 8</a>. Finally, if the emissions of current are so +ordered that their intensity alternately increases +and diminishes, the curve takes the form represented +in <a href="#il_9">fig. 9</a>. In the first case, the currents are <em>intermittent</em>; +in the second, <em>pulsatory</em>; in the third +case, they are <em>undulatory</em>.</p> + +<figure id="il_7" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p040.jpg" width="935" height="635" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 7.</span> + </figcaption> +</figure> + +<figure id="il_8" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p041.jpg" width="1024" height="655" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 8.</span> + </figcaption> +</figure> + +<figure id="il_9" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p041b.jpg" width="1024" height="753" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 9.</span> + </figcaption> +</figure> + +<p>These currents are necessarily positive or negative, +according to their position above or below the +line <i>x</i>, and if they are alternately reversed, the +curves present the form given in <a href="#il_10">fig. 10</a>, curves +which essentially differ from the first, not merely +in the different form of the indentations, but +especially in the suppression of the extra current,<span class="pagenum" id="Page_42">42</span> +which is always found in the pulsatory and undulatory +currents.</p> + +<figure id="il_10" class="figcenter" style="max-width: 25em;"> + <img src="images/i_p042.jpg" width="993" height="741" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 10.</span> + </figcaption> +</figure> + +<p>The two former systems of currents have long +been in use for the electric transmission of musical +sounds, of which we have an interesting example +in Reiss’s telephone already described. But Mr. +Bell claims to have been the first to employ the +undulatory currents, which made it possible to solve +the problem of transmitting speech.<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">3</a> In order to +estimate the importance of this discovery, it will be +enough to analyse the effects produced with these<span class="pagenum" id="Page_43">43</span> +different systems of currents when several notes of +varying pitch are to be combined.</p> + +<p><a href="#il_7">Fig. 7</a> shows a combination in which the styles +<i>a</i>, <i>a′</i>, of two sending instruments cause the interruption +of the current from the same battery +<span class="allsmcap">B</span>, so that the given vibrations should be between +them in the relation of a tierce major, that is in the +relation of four to five. Under such conditions, the +currents are intermittent, and four contacts of <i>a</i> are +produced in the same space of time as the five +contacts of <i>a′</i>, and the corresponding electric intensities +will be represented by the indentations we +see in <span class="allsmcap">A</span><sup>2</sup> and in <span class="allsmcap">B</span><sup>2</sup>: the combination of these intensities +<span class="allsmcap">A</span><sup>2</sup> + <span class="allsmcap">B</span><sup>2</sup> will produce the indentations at +unequal intervals which may be observed on the +third line. It is evident that although the current +maintains a uniform intensity, there is less time +for the breaks when the interrupting styles act +together than when they act separately, so that +when there are a number of contacts effected simultaneously +by styles working at different degrees +of velocity, the effects produced will have the effect +of a continuous current. The maximum number +of distinct effects which can be produced in this +way will, however, greatly depend on the relation +which exists between the durations of the make +and break of the current. The shorter the contacts +are, and the longer the breaks, the more numerous +will be the effects transmitted without confusion, +and <i lang="la">vice versâ</i>.</p> + +<p><span class="pagenum" id="Page_44">44</span></p> + +<p>By the aid of pulsatory currents the transmission +of musical sounds is effected in the way indicated +in <a href="#il_8">fig. 8</a>, and it is seen that when they are produced +simultaneously, the result <span class="allsmcap">A</span><sup>2</sup> + <span class="allsmcap">B</span><sup>2</sup> is analogous to +that which would be produced by a continuous +current of minimum intensity.</p> + +<p>In the case of undulatory currents the result is +different, but in order to produce them it is necessary +to have recourse to inductive effects, and <a href="#il_9">fig. 9</a> +indicates the manner in which the experiment +should be made. In this case, ‘the current from +the battery <span class="allsmcap">B</span> is thrown into waves by the inductive +action of iron or steel reeds <span class="allsmcap">M</span>, <span class="allsmcap">M</span>, vibrated in front +of electro-magnets <i>e</i>, <i>e</i>, placed in circuit with the +battery: <span class="allsmcap">A</span><sup>2</sup> and <span class="allsmcap">B</span><sup>2</sup> represent the undulations caused +in the current by the vibration of the magnetised +bodies, and it will be seen that there are four undulations +of <span class="allsmcap">B</span><sup>2</sup> in the same time as five undulations +of <span class="allsmcap">A</span><sup>2</sup>. The resultant effect upon the main line is +expressed by the curve <span class="allsmcap">A</span><sup>2</sup> + <span class="allsmcap">B</span><sup>2</sup>, which is the algebraical +sum of the sinusoidal curves <span class="allsmcap">A</span><sup>2</sup> and <span class="allsmcap">B</span><sup>2</sup>. A +similar effect is produced when reversed undulatory +currents are employed, as in <a href="#il_10">fig. 10</a>, where the current +is produced by the vibration of permanent magnets +united upon a circuit, without a voltaic battery.</p> + +<p>‘It will be understood from <a href="#il_9">figs. 9</a> and <a href="#il_10">10</a> that +the effect of transmitting musical signals of different +pitches simultaneously along a single wire +is not to obliterate the vibratory character of the +current, as in the case of intermittent and pulsatory<span class="pagenum" id="Page_45">45</span> +currents, but to change the shapes of the electrical +undulations. In fact, the effect produced upon the +current is precisely analogous to the effect produced +in the air by the vibration of the inducing +bodies <span class="allsmcap">M</span>, <span class="allsmcap">M′</span>. Hence it should be possible to +transmit as many musical tones simultaneously +through a telegraph wire as through the air.’</p> + +<figure id="il_11" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p046.jpg" width="932" height="760" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 11.</span> + </figcaption> +</figure> + +<p>After applying these principles to the construction +of a telegraphic system for multiple transmissions, +Mr. Bell lost no time in making use of +his researches to improve the vocal training of deaf +mutes. ‘It is well known,’ he said, ‘that deaf +mutes are dumb merely because they are deaf, +and that there is no defect in their vocal organs to +incapacitate them from utterance. Hence it was +thought that my father’s system of pictorial symbols, +popularly known as visible speech, might prove a +means whereby we could teach the deaf and dumb +to use their vocal organs and to speak. The great +success of these experiments urged upon me the +advisability of devising methods of exhibiting the +vibrations of sound optically, for use in teaching +the deaf and dumb. For some time I carried on +experiments with the manometric capsule of Koenig, +and with the phonautograph of Léon Scott. The +scientific apparatus in the Institute of Technology +in Boston was freely placed at my disposal for +these experiments, and it happened that at that +time a student of the Institute of Technology, Mr. +Maurey, had invented an improvement upon the<span class="pagenum" id="Page_46">46</span> +phonautograph. He had succeeded in vibrating +by the voice a stylus of wood about a foot in length +which was attached to the membrane of the phonautograph, +and in this way he had been enabled to +obtain enlarged tracings upon a plane surface of +smoked glass. With this apparatus I succeeded in +producing very beautiful tracings of the vibrations +of the air for vowel sounds. Some of these tracings +are shown in <a href="#il_11">fig. 11</a>. I was much struck with this +improved form of apparatus, and it occurred to me +that there was a remarkable likeness between the +manner in which this piece of wood was vibrated +by the membrane of the phonautograph and the<span class="pagenum" id="Page_47">47</span> +manner in which the <i lang="la">ossiculæ</i> of the human ear +were moved by the tympanic membrane. I determined +therefore to construct a phonautograph +modelled still more closely upon the mechanism +of the human ear, and for this purpose I sought +the assistance of a distinguished aurist in Boston,<span class="pagenum" id="Page_48">48</span> +Dr. Clarence J. Blake. He suggested the use of the +human ear itself as a phonautograph, instead of +making an artificial imitation of it. The idea was +novel, and struck me accordingly, and I requested +my friend to prepare a specimen for me, which he +did. The apparatus, as finally constructed, is +shown in <a href="#il_12">fig. 12</a>. The <em>stapes</em> was removed, and a +stylus of hay about an inch in length was attached +to the end of the <em>incus</em>. Upon moistening +the <em>membrana tympani</em> and the <em>ossiculæ</em> with +a mixture of glycerine and water, the necessary +mobility of the parts was obtained; and upon singing +into the external artificial ear the stylus of hay +was thrown into vibration, and tracings were obtained +upon a plane surface of smoked glass passed +rapidly underneath. While engaged in these experiments +I was struck with the remarkable disproportion +in weight between the membrane and +the bones that were vibrated by it. It occurred to +me that if a membrane as thin as tissue paper +could control the vibration of bones that were, +compared to it, of immense size and weight, why +should not a larger and thicker membrane be able +to vibrate a piece of iron in front of an electro-magnet, +in which case the complication of steel +rods shown in my first form of telephone, could be +done away with, and a simple piece of iron attached +to a membrane be placed at either end of the +telegraphic circuit?</p> + +<figure id="il_12" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p047.jpg" width="948" height="1141" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 12.</span> + </figcaption> +</figure> + +<p>‘For this purpose I attached the reed <span class="allsmcap">A</span> (<a href="#il_13">fig. 13</a>)<span class="pagenum" id="Page_49">49</span> +loosely by one extremity to the uncovered pole +<i>h</i> of the magnet, and fastened the other extremity +to the centre of a stretched membrane of goldbeaters’ +skin <i>n</i>. I presumed that upon speaking in +the neighbourhood of the membrane <i>n</i>, it would be +thrown into vibration and cause the steel reed <span class="allsmcap">A</span> +to move in a similar manner, occasioning undulations +in the electrical current that would correspond +to the changes in the density of the air during the +production of the sound; and I further thought +that the change of the intensity of the current at +the receiving end would cause the magnet there to +attract the reed <span class="allsmcap">A′</span> in such a manner that it should +copy the motion of the reed <span class="allsmcap">A</span>, in which case its +movements would occasion a sound from the membrane +<i>n′</i> similar in <em>timbre</em> to that which had occasioned +the original vibration.</p> + +<figure id="il_13" class="figcenter" style="max-width: 19em;"> + <img src="images/i_p049.jpg" width="729" height="313" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 13.</span> + </figcaption> +</figure> + +<figure id="il_14" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p050.jpg" width="923" height="563" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 14.</span> + </figcaption> +</figure> + +<p>‘The results, however, were unsatisfactory and +discouraging. My friend Mr. Thomas A. Watson, +who assisted me in this first experiment, declared +that he heard a faint sound proceed from the telephone +at his end of the circuit, but I was unable<span class="pagenum" id="Page_50">50</span> +to verify his assertion. After many experiments +attended by the same only partially successful +results, I determined to reduce the size and weight +of the spring as much as possible. For this purpose +I fastened a piece of clock spring, about the size +and shape of my thumbnail, firmly to the centre of +the diaphragm, and had a similar instrument at the +other end (<a href="#il_14">fig. 14</a>); we were then enabled to obtain +distinctly audible effects. I remember an experiment +made with this telephone, which at the time +gave me great satisfaction and delight. One of +the telephones was placed in my lecture-room in +the Boston University, and the other in the basement +of the adjoining building. One of my +students repaired to the distant telephone to observe +the effects of articulate speech, while I uttered +the sentence, “Do you understand what I say?”<span class="pagenum" id="Page_51">51</span> +into the telephone placed in the lecture-hall. To +my delight an answer was returned through the +instrument itself, articulate sounds proceeded from +the steel spring attached to the membrane, and I +heard the sentence, “Yes, I understand you perfectly.” +It is a mistake, however, to suppose that +the articulation was by any means perfect, and expectancy +no doubt had a great deal to do with my +recognition of the sentence; still, the articulation +was there, and I recognised the fact that the indistinctness +was entirely due to the imperfection of +the instrument. I will not trouble you by detailing +the various stages through which the apparatus +passed, but shall merely say that after a time I +produced the form of instrument shown in <a href="#il_15">fig. 15</a>, +which served very well as a receiving telephone. +In this condition my invention was exhibited at the +Centennial Exhibition in Philadelphia. The telephone +shown in <a href="#il_14">fig. 14</a> was used as a transmitting<span class="pagenum" id="Page_52">52</span> +instrument, and that in <a href="#il_15">fig. 15</a> as a receiver, so +that vocal communication was only established in +one direction.</p> + +<figure id="il_15" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p051.jpg" width="823" height="489" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 15.</span> + </figcaption> +</figure> + +<p>‘The articulation produced from the instrument +shown in <a href="#il_15">fig. 15</a> was remarkably distinct, but its +great defect consisted in the fact that it could not +be used as a transmitting instrument, and thus two +telephones were required at each station, one for +transmitting and one for receiving spoken messages.</p> + +<p>‘It was determined to vary the construction of +the telephone, and I sought by changing the size +and tension of the membrane, the diameter and +thickness of the steel spring, the size and power of +the magnet, and the coils of insulated wire around +their poles, to discover empirically the exact effect +of each element of the combination, and thus to +deduce a more perfect form of apparatus. It was +found that a marked increase in the loudness of the +sounds resulted from shortening the length of the +coils of wire, and by enlarging the iron diaphragm +which was glued to the membrane. In the latter +case, also, the distinctness of the articulation was +improved. Finally, the membrane of goldbeaters’ +skin was discarded entirely, and a simple iron plate +was used instead, and at once intelligible articulation +was obtained. The new form of instrument is +that shown in <a href="#il_16">fig. 16</a>, and, as had been long anticipated, +it was proved that the only use of the battery +was to magnetise the iron core of the magnet, for<span class="pagenum" id="Page_53">53</span> +the effects were equally audible when the battery +was omitted and a rod of magnetised steel substituted +for the iron core of the magnet.</p> + +<p>‘It was my original intention, and it was always +claimed by me, that the final form of telephone +would be operated by permanent magnets in place +of batteries, and numerous experiments had been +carried on by Mr. Watson and myself privately for +the purpose of producing this effect.</p> + +<figure id="il_16" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p053.jpg" width="769" height="433" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 16.</span> + </figcaption> +</figure> + +<p>‘At the time the instruments were first exhibited +in public the results obtained with permanent +magnets were not nearly so striking as when a +voltaic battery was employed, wherefore we thought +it best to exhibit only the latter form of instrument.</p> + +<p>‘The interest excited by the first published +accounts of the operation of the telephone led many +persons to investigate the subject, and I doubt not +that numbers of experimenters have independently<span class="pagenum" id="Page_54">54</span> +discovered that permanent magnets might be employed +instead of voltaic batteries. Indeed one +gentleman, Professor Dolbear, of Tufts College, +not only claims to have discovered the magneto-electric +telephone, but I understand charges me +with having obtained the idea from him through the +medium of a mutual friend.</p> + +<figure id="il_17" class="figcenter" style="max-width: 13em;"> + <img src="images/i_p054.jpg" width="503" height="325" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 17.</span> + </figcaption> +</figure> + +<p>‘A still more powerful form of apparatus was +constructed by using a powerful compound horseshoe +magnet in place of the straight rod which had +been previously used (see <a href="#il_17">fig. 17</a>). Indeed the +sounds produced by means of this instrument were +of sufficient loudness to be faintly audible to a +large audience, and in this condition the instrument +was exhibited in the Essex Institute, in Salem, +Massachusetts, on February 12, 1877, on which +occasion a short speech shouted into a similar +telephone in Boston, sixteen miles away, was heard +by the audience in Salem. The tones of the +speaker’s voice were distinctly audible to an +audience of 600 people, but the articulation was<span class="pagenum" id="Page_55">55</span> +only distinct at a distance of about 6 feet. On the +same occasion, also, a report of the lecture was +transmitted by word of mouth from Salem to +Boston, and published in the papers the next +morning.</p> + +<figure id="il_18" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p055.jpg" width="815" height="453" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 18.</span> + </figcaption> +</figure> + +<p>‘From the form of telephone shown in <a href="#il_16">fig. 16</a> +to the present form of the instrument (<a href="#il_18">fig. 18</a>) is +but a step. It is in fact the arrangement of <a href="#il_16">fig. 16</a> +in a portable form, the magnet <span class="allsmcap">N S</span> being placed +inside the handle, and a more convenient form of +mouthpiece provided.</p> + +<p>‘And here I wish to express my indebtedness +to several scientific friends in America for their co-operation +and assistance. I would specially mention +Professor Peirce and Professor Blake, of Brown +University, Dr. Channing, Mr. Clarke, and Mr. +Jones. It was always my belief that a certain ratio +would be found between the several parts of a +telephone, and that the size of the instrument was<span class="pagenum" id="Page_56">56</span> +immaterial; but Professor Peirce was the first to +demonstrate the extreme smallness of the magnets +which might be employed. The convenient form +of mouthpiece shown in <a href="#il_17">fig. 17</a>, now adopted by +me, was invented solely by my friend Professor +Peirce.’</p> + +<figure id="il_19" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p056.jpg" width="781" height="840" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 19.</span> + </figcaption> +</figure> + +<p>Another form of transmitting telephone exhibited +in Philadelphia, intended for use with the +receiving telephone (<a href="#il_15">fig. 15</a>), is represented by <a href="#il_19">fig. 19</a>.</p> + +<p>A platinum wire attached to a stretched membrane +completed a voltaic circuit by dipping into +water. Upon speaking to the membrane, articulate<span class="pagenum" id="Page_57">57</span> +sounds proceeded from the telephone in the distant +room. The sounds produced by the telephone +became louder when dilute sulphuric acid, or a +saturated solution of salt, was substituted for the +water. Audible effects were also produced by the +vibration of plumbago in mercury, in a solution of +bichromate of potash, in salt and water, in dilute +sulphuric acid, and in pure water.</p> + +<p>Mr. Bell goes on to say:</p> + +<p>‘I have found also that a musical tone proceeds +from a piece of plumbago or retort carbon when +an intermittent current of electricity is passed +through it, and I have observed the most curious +audible effects produced by the passage of reversed +intermittent currents through the human body. A +rheotome was placed in circuit with the primary +wires of an induction coil, and the fine wires were +connected with two strips of brass. One of +these strips was held closely against the ear, and a +loud sound proceeded from it whenever the other +slip was touched with the other hand. The +strips of brass were next held one in each hand. The +induced currents occasioned a muscular tremor in +the fingers. Upon placing my forefinger to my +ear a loud crackling noise was audible, seemingly +proceeding from the finger itself. A friend who +was present placed my finger to his ear, but heard +nothing. I requested him to hold the strips himself. +He was then distinctly conscious of a noise +(which I was unable to perceive) proceeding from<span class="pagenum" id="Page_58">58</span> +his finger. In this case a portion of the induced +currents passed through the head of the observer +when he placed his ear against his own finger; and it +is possible that the sound was occasioned by a vibration +of the surfaces of the ear and finger in contact.</p> + +<p>‘When two persons receive a shock from a +Ruhmkorff’s coil by clasping hands, each taking +hold of one wire of the coil with the free hand, a +sound proceeds from the clasped hands. The +effect is not produced when the hands are moist. +When either of the two touches the body of the +other, a loud sound comes from the parts in contact. +When the arm of one is placed against the arm of +the other, the noise produced can be heard at a +distance of several feet. In all these cases a +slight shock is experienced so long as the contact +is preserved. The introduction of a piece of paper +between the parts in contact does not materially +interfere with the production of the sounds, but +the unpleasant effects of the shock are avoided.</p> + +<p>‘When an intermittent current from a Ruhmkorff’s +coil is passed through the arms, a musical +note can be perceived when the ear is closely +applied to the arm of the person experimented +upon. The sound seems to proceed from the +muscles of the fore-arm and from the biceps +muscle. Mr. Elisha Gray<a id="FNanchor_4" href="#Footnote_4" class="fnanchor">4</a> has also produced +audible effects by the passage of electricity through +the human body.</p> + +<p><span class="pagenum" id="Page_59">59</span></p> + +<p>‘An extremely loud musical note is occasioned +by the spark of a Ruhmkorff’s coil when the +primary circuit is made and broken with sufficient +rapidity; when two rheotomes of different pitch are +caused simultaneously to open and close the primary +circuit, a double tone proceeds from the spark.</p> + +<p>‘A curious discovery, which may be of interest +to you, has been made by Professor Blake. He +constructed a telephone in which a rod of soft iron, +about six feet in length, was used instead of a permanent +magnet. A friend sang a continuous +musical tone into the mouthpiece of a telephone, +like that shown in <a href="#il_17">fig. 17</a>, which was connected +with the soft iron instrument alluded to above. +It was found that the loudness of the sound produced +in this telephone varied with the direction in +which the iron rod was held, and that the maximum +effect was produced when the rod was in the position +of the dipping-needle. This curious discovery +of Professor Blake has been verified by myself.</p> + +<p>‘When a telephone is placed in circuit with a +telegraph line, the telephone is found seemingly to +emit sounds on its own account. The most extraordinary +noises are often produced, the causes of +which are at present very obscure. One class of +sounds is produced by the inductive influence of +neighbouring wires and by leakage from them, the +signals of the Morse alphabet passing over neighbouring +wires being audible in the telephone, and +another class can be traced to earth currents upon<span class="pagenum" id="Page_60">60</span> +the wire, a curious modification of this sound revealing +the presence of defective joints in the wire.</p> + +<p>‘Professor Blake informs me that he has been +able to use the railroad track for conversational +purposes in place of a telegraph-wire, and he +further states that when only one telephone was +connected with the track the sounds of Morse +operating were distinctly audible in the telephone, +although the nearest telegraph-wires were at least +forty feet distant; and Professor Peirce has observed +the most curious sounds produced from a telephone +in connection with a telegraph-wire during the +aurora borealis.’</p> + +<p>Mr. Bell went on to describe instances in +which airs sung or played upon a musical instrument +are transmitted by a telephone, when it is +not known whence they come; but the strongest +proof of the extraordinary sensibility of this +instrument consists in its becoming possible by its +means to transmit speech through bodies which +might be supposed to be non-conductors. Thus +communication with the earth through the human +body can be made in spite of the intervention of +shoes and stockings; and it may even be effected +if, instead of standing on the ground, the person +stands on a brick wall. Only hewn stone and +wood are a sufficient hindrance to communication, +and if the foot touches the adjoining ground, or +even a blade of grass, it is enough to produce +electric manifestations.</p> + +<p><span class="pagenum" id="Page_61">61</span></p> + +<p>Mr. Bell says in conclusion:</p> + +<p>‘The question will naturally arise, Through +what length of wire can the telephone be used? +In reply to this, I may say that the maximum +amount of resistance through which the undulatory +current will pass, and yet retain sufficient force to +produce an audible sound at the distant end, has +yet to be determined; no difficulty has, however, +been experienced in laboratory experiments in +conversing through a resistance of 60,000 ohms, +which has been the maximum at my disposal. +On one occasion, not having a rheostat at hand, I +may mention having passed the current through +the bodies of sixteen persons, who stood hand in +hand. The longest length of real telegraph line +through which I have attempted to converse has +been about 250 miles. On this occasion no +difficulty was experienced so long as parallel lines +were not in operation. Sunday was chosen as the +day on which it was probable other circuits would +be at rest. Conversation was carried on between +myself in New York, and Mr. Thomas A. Watson +in Boston, until the opening of business upon the +other wires. When this happened the vocal +sounds were very much diminished, but still audible. +It seemed, indeed, like talking through a storm. +Conversation, though possible, could be carried on +with difficulty, owing to the distracting nature of +the interfering currents.</p> + +<p>‘I am informed by my friend Mr. Preece that<span class="pagenum" id="Page_62">62</span> +conversation has been successfully carried on +through a submarine cable, sixty miles in length, +extending from Dartmouth to the Island of +Guernsey, by means of hand telephones.’</p> + +<figure id="il_20" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p062.jpg" width="906" height="742" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 20.</span> + </figcaption> +</figure> + +<p><i>Mr. Elisha Gray’s Share in the Invention of the +Telephone.</i>—We have seen that if Mr. Bell was the +first to construct the speaking telephone in a practical +form, Mr. Gray had at the same time conceived +the idea of an instrument also capable of reproducing +speech, and the description given of it in +his <i lang="la">caveat</i> was so precise that if it had been made +from his design, it would have acted perfectly. +This was, in fact, afterwards proved by him. In +order that our readers may judge from their own<span class="pagenum" id="Page_63">63</span> +knowledge of the share which should be ascribed to +Mr. Elisha Gray in the invention of the telephone, +we reproduce in <a href="#il_20">fig. 20</a> the drawing which accompanied +the <i lang="la">caveat</i> in question.</p> + +<p>The sender, as we see, is composed of a sort +of tube, closed at its lower end by a membrane +to which a platinum wire is fixed; this wire dips +into a liquid of moderate conducting power, and +an electrode made of platinum, in communication +with a battery, is fixed at the bottom of the +vessel containing the liquid. The receiver is composed +of an electro-magnet, of which the armature +is fixed to the centre of a membrane, stretched +on a kind of resonator or ear-trumpet which is +held to the ear, and the two instruments are united +by the line wire as we see in the plate.</p> + +<p>Under these conditions, the undulatory currents +necessary for the reproduction of speech were obtained +in a mode analogous to that pointed out by +Mr. Bell in his specification, that is, by the variations +of resistance in the liquid layer interposed +between the platinum wires of the transmitter; +and their action, exerted on an electro-magnet, of +which the armature was fixed on the diaphragm of +the resonator, was produced under more favourable +conditions than in Mr. Bell’s specification (see +<a href="#il_13">fig. 13</a>), since that gentleman regards this arrangement +(represented in <a href="#il_14">fig. 14</a>) as an important improvement +on his first conception.</p> + +<p>The whole importance of the invention rests<span class="pagenum" id="Page_64">64</span> +on the intervention of undulatory currents, which, +as we have seen, are indispensable for the reproduction +of speech, and it concerns us to know +whether it was Mr. Bell or Mr. Gray who first declared +their importance; for in both the specifications +deposited on February 14, 1876, the use of +undulatory currents was declared to be indispensable. +Mr. Gray asserts that he had recognised +their importance for the transmission of combined +sounds as early as 1874; but Mr. Bell believes that +the undulatory currents mentioned by Mr. Gray at +that time were only currents analogous to those he +had designated under the name of pulsatory currents, +which we have represented in <a href="#il_8">fig. 8</a>. We +have seen that since these currents only represent +the abrupt elevations and depressions of intensity, +they are unfit for the reproduction of articulate +sounds, which, on the contrary, demand that the +variations of intensity should result from successive +efforts, in exact correspondence with all the +inflections of the sonorous vibrations effected by +the voice. Mr. Bell’s claim to priority on this question +has been recognised by the American Patent +Office, since he has been placed in possession of +the patent. However this may be, Mr. Gray’s +telephonic system was complete, and we see in it, +as we have already said, the origin of the battery +telephones, which have recently produced such important +results. Let us now consider the relation +which this system bears to Mr. Bell’s.</p> + +<p><span class="pagenum" id="Page_65">65</span></p> + +<p>The Bell system, as we have seen, although +making use of a battery in the first instance, only +obtained the diminution and increase of electric +force necessary for the articulation of words by +means of induction currents produced by the +movements of an armature of soft iron, currents +of which the intensity was consequently due to the +range and inflections of these movements. The +battery only intervened in order to communicate +magnetic force to the inducer. This use of induced +currents in telephonic transmissions was +already of great importance, since various experiments +subsequently made have proved their superiority +to voltaic currents for this purpose. But +experience soon convinced Mr. Bell that a powerful +inductive apparatus worked by a battery was +not only unnecessary for the action of this apparatus, +but that a permanent magnet, very small and +weak, would provide sufficient currents. This discovery, +in which, as we have seen, Mr. Peirce had +some share, was of great importance, since it became +possible to reduce the size of the instrument considerably, +so as to make it portable and adapted +for sending and receiving; and it was shown that +the telephone was the most sensitive of all instruments +in revealing the action of currents. If, +therefore, Mr. Bell was not the first to employ the +successful mode of transmitting articulate words, it +must be said that he sought, like Mr. Gray, to solve +the problem by means of undulatory currents, and<span class="pagenum" id="Page_66">66</span> +that he obtained these currents by the effect of induction, +a system which, as soon as it was perfected, +led to the important results with which we are all +acquainted. If he had only given to the astonished +world an instrument capable of reproducing +speech telegraphically, his fame would be great; +for this problem had hitherto been regarded as +insoluble.</p> + +<p>Mr. Gray’s claims to the invention of the telephone +are given in the following summary from +a very interesting work, entitled ‘Experimental +Researches on Electro-harmonic Telegraphy and +Telephony:’</p> + +<p>‘1. I was the first to discover the means of +transmitting compound sounds and variable inflections +through a closed circuit by means of two or +more electric waves.</p> + +<p>‘2. I assert that I was the first to discover and +utilise the mode of reproducing vibrations by the +use of a magnet receiver constantly supplied with +electric action.</p> + +<p>‘3. I also assert that I was the first to construct +an instrument consisting of a magnet with a circular +diaphragm of magnetic substance, supported by +its edge at a little distance from the poles of a +magnet, and capable of being applied to the transmission +and reception of articulate sounds.’</p> + +<p>It is a curious fact, worth recording here, that +Mr. Yates, of Dublin, in 1865, when trying to improve +Reiss’s telephone, realised to a certain extent<span class="pagenum" id="Page_67">67</span> +Mr. Gray’s conception of the liquid transmitter; for +he introduced into the platinum contacts of Mr. +Reiss’s instrument a drop of water which adapted +it for the reproduction of articulate sounds. However, +no notice was then taken of this result.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="EXAMINATION_INTO_THE_FUNDAMENTAL_PRINCIPLES"><span id="toclink_67"></span>EXAMINATION INTO THE FUNDAMENTAL PRINCIPLES +ON WHICH BELL’S TELEPHONE IS BASED.</h2> +</div> + +<p>Although the preceding account would suffice +to make the principle of Bell’s telephone intelligible +to persons acquainted with electric science, +this would not be the case with the majority of +our readers, and we therefore think it necessary +to enter into some details as to the source of the +electric currents which are employed in telephonic +transmissions. These details seem to us the more +necessary, since many persons still believe that +Bell’s telephones are not electric, because they do +not require a battery, and they are often confounded +with string telephones, so that the difference +of price between Bell’s instruments and +those hawked in the streets seems astonishing.</p> + +<p>Without defining what is meant by an electric +current, which would be too elementary, we may +say that electric currents can be produced by different +causes, and that, in addition to those which +are due to batteries, strong currents are also produced +by the force exerted by magnets on a conducting +circuit properly arranged. Such currents<span class="pagenum" id="Page_68">68</span> +are called induction currents, and are used in Bell’s +telephone. In order to understand how they are +developed under these conditions, it will be enough +to examine what takes place when the pole of a +magnet is brought near to, and withdrawn from, a +closed circuit. To do this, let us suppose a copper +wire attached to a galvanometer in the form of a +circle, and that one pole of a permanent magnet is +directed towards the centre of the circle. Now +observe what happens:</p> + +<p>1. At the moment when the magnet approaches +an electric current arises, causing the galvanometer +to deviate to one side. This deviation will be great +in proportion to the extent of the movement, and +the tension of the current will be great in proportion +to the abruptness of the movement. The +current will however be only instantaneous.</p> + +<p>2. At the moment when the magnet is withdrawn, +a fresh current of the same nature will arise, +but it will appear in an opposite direction from the +former. It will be what is called a direct current, +because it is in the same direction as the magnetic +current of the magnet which produces it, while the +other current is called <em>inverse</em>.</p> + +<p>3. If, instead of advancing or withdrawing the +magnet by means of a single movement, it is +advanced in jerks, a succession of currents in the +same direction is produced, of which the existence +can be ascertained by the galvanometer when +there is a sufficient interval between the movements,<span class="pagenum" id="Page_69">69</span> +but when the intervals are very slight the currents +are interfused; and since inverse effects take place +when the magnet is moved in a contrary direction, +the needle of the galvanometer follows the movements +of the magnet, and to a certain extent +stereotypes them.</p> + +<p>4. If, instead of reacting on a simple closed +circuit, the magnet exerts its force on a considerable +number of circumvolutions of this circuit, that +is, on a bobbin of coiled wire, the effects will be considerably +increased, and they will be still greater +if there be a magnetic core within the bobbin, +since the inducing action will then be more effectually +exerted throughout the bobbin. As the +magnetic core, when it is magnetised and demagnetised +under the influence of its approach to or +withdrawal from the inducing magnet, is subject to +the reaction from all the fluctuations which occur in +the movements of the magnet, the induced currents +which ensue are perfectly defined.</p> + +<p>5. If, instead of a movable magnet, we suppose +it to be fixed in the centre of the coil, the +induced currents of which we have spoken may +then be determined by modifying its force. In +order to do so, it is enough that an iron armature +should react upon its poles. When this armature +is brought close to one of the poles, or to both at +once, it acquires force, and produces an inverse +current, that is, a current in the direction which +would have corresponded to an approach of the<span class="pagenum" id="Page_70">70</span> +magnet to the closed circuit. On its withdrawal +the inverse effect is produced; but in both cases the +induced currents correspond with the extent and +direction of the movements accomplished by the +armature, and consequently they may reproduce +its movements by their effects. If this armature is +an iron plate, which vibrates under the influence +of any sound in this disposition of the electro-magnetic +system, the alternate movements of the +plate will be transformed into the induced currents, +and these will be stronger or weaker, more or less +definite, according to the range and complexity of +the vibrations: they will, however, be undulatory, +since they will always result from successive and +continuous movements, and will consequently be +in the conditions which, as we have seen, are required +for the transmission of speech.</p> + +<p>As for the action produced upon the receiver, +that is, on the instrument for reproducing speech, +it is somewhat complex, and we shall have occasion +to speak of it presently; but we can get a general +impression of it, if we consider that the effects +produced by the induced currents of variable +intensity, which traverse the coil of the electro-magnetic +system, must determine, by the magnetisations +and demagnetisations which ensue, the +vibrations of the armature disk; these vibrations, +more or less amplified and defined, exactly represent +those of the disk before which the speaker +stands, and can only be obtained from them. The<span class="pagenum" id="Page_71">71</span> +effects are, however, in reality more complex, +although they are produced under analogous conditions, +and we shall have more to say about +them when we come to speak of the experiments +made with the telephone. It must meanwhile be +observed that, for the reproduction of speech, it is +not necessary that the magnetic core should be of +soft iron, since the vibratory effects may follow +from differential as well as from direct magnetisation.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="ORDINARY_ARRANGEMENT_OF_THE_BELL"><span id="toclink_71"></span>ORDINARY ARRANGEMENT OF THE BELL +TELEPHONE.</h2> +</div> + +<p>The arrangement most generally adopted for +the telephone is the one represented in <a href="#il_21">fig. 21</a>. +It consists of a kind of circular wooden box, fitted +to the extremity of a handle <span class="allsmcap">M</span>, which is also of +wood, and contains the magnetic bar <span class="allsmcap">N S</span>. This +bar is fixed by means of a screw <i>t</i>, and is so +arranged as to be moved forward and backward by +tightening or loosening the screw, a condition +necessary in order to regulate the instrument. At +the free extremity of the bar the magnetic coil +<span class="allsmcap">B</span> is fixed; this must, according to MM. Pollard +and Garnier, be made of wire No. 42, so as to present +a considerable number of spirals. The ends +of this coil generally terminate at the lower end of +the handle in two copper rods <i>f</i>, <i>f</i>, which traverse +its length, and are fastened to two binding-screws<span class="pagenum" id="Page_72">72</span> +<span class="allsmcap">I</span>, <span class="allsmcap">I′</span>, where the line wires <span class="allsmcap">C</span>, <span class="allsmcap">C</span> are fixed. In the +instruments made by M. Bréguet there are, however, +no binding-screws, but a little twist, made of +two flexible wires covered with gutta-percha and +silk, is fastened to the two rods. A wooden cap is +screwed to the end of the handle, and the twist +passes through a hole made in this cap, so that +there is no inconvenience in working the instrument. +By laying hold of the ends of the wire twist +with pliers it is possible to join them to the circuit. +This instrument is represented in <a href="#il_22">fig. 22</a>.</p> + +<figure id="il_21" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p072.jpg" width="807" height="457" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 21.</span> + </figcaption> +</figure> + +<p>By another arrangement, the wires of the coil +end immediately in the binding-screws which are +placed below the wooden box, but this arrangement +is inconvenient.</p> + +<p>Above the pole of the magnetic bar is placed +the iron vibrating plate <span class="allsmcap">L L</span>, which is coated either +with black or yellow varnish, with tin or blue oxide, +but which must always be very thin. This plate<span class="pagenum" id="Page_73">73</span> +is in the form of a disk, and by its rim, resting on a +caoutchouc ring, it is firmly fixed to the circular +edges of the wooden box, which is for this purpose +made in two pieces. These pieces are adjusted to<span class="pagenum" id="Page_74">74</span> +each other, either by screws or by spirals cut in +half the thickness of the wood. This disk ought to +be as near as possible to the polar end of the +magnet, yet not so near as to produce contact +between the two by the vibrations of the voice. +Finally, the mouthpiece <span class="allsmcap">R R′</span> (<a href="#il_21">fig. 21</a>), which is in +form of a wide funnel, terminates the upper part of +the box, and should be so arranged as to leave a +certain space between the disk and the edges of +the hole <span class="allsmcap">V</span>, which is open in its centre. The size of +the box should be so calculated as to permit of its +acting as a sounding-box, without however provoking +echoes and a confusion of sounds.</p> + +<figure id="il_22" class="figcenter" style="max-width: 12em;"> + <img src="images/i_p073.jpg" width="616" height="1263" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 22.</span> + </figcaption> +</figure> + +<p>When the instrument is properly made, it will +produce very marked effects; and M. Pollard, one +of the first Frenchmen to take up the study of +telephones, has written as follows on the subject:</p> + +<p>‘The instrument which I have prepared gives +results which are truly astonishing. In the first +place, when considering the resistance, the introduction +into the circuit of five or six persons does +not sensibly diminish the intensity of sounds. On +putting an instrument to each ear, the sensation is +precisely the same as if the correspondent were +speaking some yards behind. The intensity, the +clearness, the purity of tone are irreproachable.</p> + +<p>‘I can speak to my colleague in quite an undertone, +scarcely breathing as I may say, and persons +placed within two yards of me will be unable to +catch a single word of our conversation.</p> + +<p><span class="pagenum" id="Page_75">75</span></p> + +<p>‘On the part of the receiver, if anyone raises +his voice to call me, I hear the call in all parts of +my office, at least when silence prevails there; at +any rate, when I am seated at my table with the +instrument some yards off, I can always hear +the call. In order to increase the intensity of +sound, I fitted the mouthpiece with a copper +horn of conical shape, and under these conditions +words spoken in my bureau two or three yards +from the mouthpiece can be heard at the other +end of the line; from my station, a little more than +a yard from the tube, I can hear and speak to my +colleague without effort.’</p> + +<p>In using the ordinary Bell telephone, it is +necessary to speak distinctly before the mouthpiece +of the telephone which is handled, while the +listener placed at the corresponding station keeps +the mouthpiece of the receiver to his ear. These +two instruments form a closed circuit with the two +wires which connect them, but one is enough to +make the transmission perfect, if care is taken to +place both instruments in connection with the +earth, which thus takes the place of the second +wire. M. Bourbouze asserts that the intensity of +sound in the telephone is much increased by employing +this expedient, but we believe that this +increase depends upon the conditions of the circuit, +although he asserts that the fact can be proved in a +circuit not exceeding eighty yards.</p> + +<p>For practical purposes it is necessary to have<span class="pagenum" id="Page_76">76</span> +two telephones at each station, so as to hold one to +the ear while speaking through the other, as in <a href="#il_23">fig. 23</a>. +It is also much more easy to hear with a +telephone applied to each ear, in which case they +are held as in <a href="#il_24">fig. 24</a>. In order not to fatigue the +arms, an arrangement has been made by which they +are held before the ears by a strap and spring which +goes round the head.</p> + +<figure id="il_23" class="figcenter" style="max-width: 16em;"> + <img src="images/i_p076.jpg" width="623" height="741" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 23.</span> + </figcaption> +</figure> + +<p>The sending power of the telephone varies +with different voices. Mr. Preece asserts that +shouting has no effect, and that, in order to obtain +a favourable result, the intonation must be clear, +the articulation distinct, and the sounds emitted +must resemble musical sounds as much as possible.</p> + +<p><span class="pagenum" id="Page_77">77</span></p> + +<p>Mr. Wilmot, one of the electricians employed +by the Post Office, says that he has been able to +make himself heard on circuits through which no +other voices were audible. The vowel sounds are +most readily transmitted, and among other letters <i>e</i>, +<i>g</i>, <i>j</i>, <i>k</i>, and <i>q</i> are always repeated more imperfectly. +The ear requires practice, and the faculty of hearing +varies in a surprising degree in different people. +Singing is very distinctly heard, as well as wind +instruments, especially the cornet-à-piston, which, +when played in London, was heard by thousands of +people in the Corn Exchange at Basingstoke.</p> + +<figure id="il_24" class="figcenter" style="max-width: 19em;"> + <img src="images/i_p077.jpg" width="737" height="688" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 24.</span> + </figcaption> +</figure> + +<p>According to Mr. Rollo Russell, it is not +necessary to isolate the circuit of a telephone when<span class="pagenum" id="Page_78">78</span> +the distance is relatively slight; thus, with a circuit +of about 430 yards, it is possible to use a simple +copper wire, laid on the grass, without destroying +the telephonic transmission from a small musical +box, as long as the two wires do not touch each +other. Transmission took place, even when the +circuit was buried in moist earth for a length of +thirty-five yards, or immersed in a well for a length +of forty-eight yards. The words transmitted under +such conditions did not differ from those transmitted +by an isolated circuit.</p> + +<p>The telephone may be heard at the same +moment by several listeners, either by connecting +the wires which unite the telephones in correspondence +(near the receiving telephone) with +branch wires of other telephones, which may be +done up to the number of five or six, in short +circuits; or by means of a little sounding-box +closed by two thin membranes, one of which is +fixed on the vibrating disk. When a certain +number of acoustic tubes are connected with the +membrane, Mr. M’Kendrick asserts that several +people can hear distinctly.</p> + +<p>Telephones may also transmit speech to different +stations simultaneously, by inserting them on +the same circuit, and experiments made at New +York showed that five instruments placed in +different parts of the same telegraphic line could be +made to speak in this way. In the telephonic experiments +made on the canal lines in the department<span class="pagenum" id="Page_79">79</span> +of the Yonne, it was ascertained that on a wire +seven miles and a half in length, on which several +telephones were placed at varying distances, three +or four persons were able to converse with each +other through the telephones, and each could +hear what the other was saying. The questions +and answers could be understood, even in crossing. +It was also possible, by placing a telephone on a +second wire, a little over five miles in length, and +half a yard distant from the other, to hear the conversation +exchanged on the first wire by following +it to a distance not exceeding a mile and a quarter. +Even the different voices of the two speakers could +be distinguished.</p> + +<p>Since the telephone made its appearance in +Europe, several inventors have asserted that they +are able to make a telephone speak so as to be +audible in all parts of a large hall. It has been +shown that this was accomplished by Mr. Bell, and +in this respect we do not see that those who have +attempted to improve the telephone have attained +results of greater importance. It is certain that +the ordinary telephone can emit musical sounds +which become perfectly audible in a tolerably +large room, while the instrument is still attached +to the wall. We should also remember the results +obtained by MM. Pollard and Garnier in the +experiments made at Cherbourg to connect the +mole with the <i lang="fr">Préfecture Maritime</i>.</p> + +<p>The mole at Cherbourg is, as we know, a kind<span class="pagenum" id="Page_80">80</span> +of artificial island thrown up before the town in +order to make an anchorage. The forts which +have been constructed on the mole are connected by +submarine cables with the military port and with +the <i lang="fr">Préfecture Maritime</i>. On one occasion, after +making experiments in the Préfet’s study on one +of the cables applied to a telephone, several persons +were talking together in the room, and were much +surprised to hear the bugle sound the retreat, the +sound appearing to come from one part of the +room. It was found, on examination, that the +telephone hung to the wall was occupied with +this performance. On enquiry, it appeared that +one of the manipulators on the mole station had +amused himself by sounding the bugle before the +telephone on that station. The mole is more than +three miles from Cherbourg, and the <i lang="fr">Préfecture Maritime</i> +is in the centre of the town. Yet these telephones +had been roughly made in the dockyard +workshops; and we have here another proof of the +small amount of accuracy required for the successful +working of these instruments.</p> + +<figure id="il_25" class="figcenter" style="max-width: 12em;"> + <img src="images/i_p081.jpg" width="540" height="1120" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 25.</span> + </figcaption> +</figure> + +<p>Telephones of various construction on the +Bell model are to be seen at M. C. Roosevelt’s, +Mr. Bell’s agent in Paris, 1, Rue de la Bourse. +They are, for the most part, constructed by M. +Bréguet, and the model in the greatest request, +exclusive of the one we have described, is the +great square model, with a horseshoe magnet enclosed +in a flat box, and a horn on its upper side,<span class="pagenum" id="Page_81">81</span> +which serves as a mouthpiece. This system is +represented in <a href="#il_25">fig. 25</a>, and it has been neatly constructed +at Boston under the best conditions. In +this new model, made by Mr. Gower, the magnet +is composed of several plates terminated by magnetic +cores of iron, to which the coils are fixed,<span class="pagenum" id="Page_82">82</span> +and the whole is covered with a thick layer of +paraffin. The sounds thus reproduced are much +stronger and more distinct. Mr. Gower, who is +now Mr. Roosevelt’s partner, has made considerable +improvements in the different forms of Mr. +Bell’s instrument. There is one model in the form +of a snuff-box, in which the magnet is twisted into +a spiral, so as to maintain its length in a circular +form. The pole, which is in the centre of the +spiral, is furnished with an iron core, to which the +induction coil is fastened, and the cover of the +snuff-box supports the vibrating disk as well as +the mouthpiece: this model is represented in <a href="#il_26">fig. 26</a>. +In another model, called the mirror telephone, +the preceding arrangement is fitted on to a handle<span class="pagenum" id="Page_83">83</span> +like the glass of a portable mirror, and there is a +mouthpiece on one of the lateral faces, so that the +speaker uses the instrument as if he were speaking +before a chimney screen.</p> + +<figure id="il_26" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p082.jpg" width="1003" height="599" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 26.</span> + </figcaption> +</figure> + +<p>Mr. Bailey has different models of telephones +worked by a battery or by the Edison carbon of +which we shall speak presently, and these, as well +as the telephones by Messrs. Gray and Phelps, +are more successful in conveying sound on a long +line of wire.</p> + +<hr class="chap x-ebookmaker-drop"> + +<h2>DIFFERENT ARRANGEMENTS OF TELEPHONES.</h2> + +<p>The prodigious results attained with the Bell +telephones, which were at first discredited by many +scientific men, necessarily provoked, as soon as their +authenticity was proved, innumerable researches +on the part of inventors, and even of those who +were originally the most incredulous. A host of +improvements and modifications have consequently +been suggested, which are evidently not without +interest, and must now be considered by us.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="BATTERY_TELEPHONES"><span id="toclink_83"></span>BATTERY TELEPHONES.</h2> +</div> + +<p><i>The Edison Telephone.</i>—One of the earliest and +most interesting improvements made in the Bell +telephone is that introduced by Mr. Edison in +the early part of the year 1876. This system is +indeed more complicated than the one we have<span class="pagenum" id="Page_84">84</span> +just considered, since it requires a battery, and +the sending instrument differs from the receiving +instrument; but it is less apt to be affected by +external causes, and transmits sound to a greater +distance.</p> + +<p>The Edison telephone, like Mr. Gray’s, which +we have already had occasion to mention, is based +upon the action of undulatory currents, determined +by the variations in the resistance of a conductor +of moderate conducting power, which is inserted in +the circuit, and the vibrations of a diaphragm before +which the speaker stands react upon it. Only, instead +of employing a liquid conductor, which is +practically useless, Mr. Edison has attempted to use +semi-conducting solid bodies. Those which were +most suitable from this point of view were graphite +and carbon, especially the carbon extracted from +compressed lamp-black. When these substances +are introduced into a circuit between two conducting +plates, one of which is moveable, they are capable +of modifying the resistance of the circuit almost in +the same proportion as the pressure exerted upon +them by the moveable plate,<a id="FNanchor_5" href="#Footnote_5" class="fnanchor">5</a> and it was seen that,<span class="pagenum" id="Page_85">85</span> +in order to obtain the undulatory currents necessary +for the production of articulate sounds, it was +enough to introduce a disk of plumbago or of lamp-black +between the vibrating plate of a telephone +and a platinum plate placed in connection with +the battery. When the telephone disk is placed +in circuit, its vibrations before the disk of carbon +produce a series of increasing and decreasing +pressures, thus causing corresponding effects in +the intensity of the transmitted current, and these +effects react in an analogous manner on the undulatory<span class="pagenum" id="Page_86">86</span> +currents determined by induction in the +Bell system. In order to obtain good results, +however, several accessory arrangements were +necessary, and we represent in <a href="#il_27">fig. 27</a> one of the +arrangements made in this part of Mr. Edison’s +telephonic system.</p> + +<figure id="il_27" class="figcenter" style="max-width: 16em;"> + <img src="images/i_p085.jpg" width="626" height="851" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 27.</span> + </figcaption> +</figure> + +<p>In <a href="#il_27">this figure</a> a section of the instrument is +given, and its form greatly resembles that of Bell. +<span class="allsmcap">L L</span> is the vibrating disk; <span class="allsmcap">O′ O</span>, the mouthpiece; <span class="allsmcap">M</span>, +the opening to the mouthpiece; <span class="allsmcap">N N N</span>, the case for +the instrument, which is, like the mouthpiece, made +of ebonite, and below the disk it presents a rather +large cavity, and a tubular hole which is scooped in +the handle. In its upper part this tube terminates +in a cylindrical rim, furnished with a worm on which +is screwed a little rod with a ridge on its inner side, +and the rheostatic system is placed within this tube. +The system consists, first, of a piston <span class="allsmcap">E</span>, fitted to +the end of a long screw <span class="allsmcap">E F</span>, and the turning of the +button will move the piston up or down within a +certain limit. Above this piston there is fitted a +very thin platinum plate <span class="allsmcap">A</span>, connected by a flexible +chain and a wire with a binding-screw <span class="allsmcap">P′</span>. Another +plate <span class="allsmcap">B</span>, exactly similar, is connected with the +binding-screw <span class="allsmcap">P</span>, and the carbon disk <span class="allsmcap">C</span> is placed +between these two plates. This disk is composed +of compressed lamp-black and petroleum, and its +resistance is one <em>ohm</em>, or 110 yards, of telegraphic +wire. Finally, an ebonite disk is fastened to the +upper platinum plate, and an elastic pad, composed<span class="pagenum" id="Page_87">87</span> +of a piece of caoutchouc tube <span class="allsmcap">G</span>, and of a cork +disk <span class="allsmcap">H</span>, is interposed between the vibrating plate +<span class="allsmcap">L L</span> and the disk <span class="allsmcap">B</span>, in order that the vibrations of +the plate may not be checked by the rigid obstacle +formed by the whole rheostatic system. When +these different parts are in position, the instrument +is regulated by the screw <span class="allsmcap">F</span>, and this is easily +done by screwing or unscrewing it until the receiving +telephone gives out its maximum of sound.</p> + +<figure id="il_28" class="figcenter" style="max-width: 16em;"> + <img src="images/i_p087.jpg" width="602" height="331" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 28.</span> + </figcaption> +</figure> + +<p>In another model, represented in <a href="#il_28">fig. 28</a>, which +has produced the best results in the distinctness +with which sounds are transmitted, the vibrating +plate <span class="allsmcap">L L</span> is supported on the disks of the secondary +carbon conductor <span class="allsmcap">C</span> by means of a little iron +cylinder <span class="allsmcap">A</span>, instead of the caoutchouc pad, and +the pressure is regulated by a screw placed below +<i>e</i>. The mouthpiece <span class="allsmcap">E</span> of the instrument is more +prominent, and its opening is larger. Finally, the +instrument, which is cased in nickel silver, is without +a handle. The rigid disk <i>b</i>, resting on the<span class="pagenum" id="Page_88">88</span> +first platinum plate <i>p</i>, is of aluminium instead of +ebonite.</p> + +<figure id="il_29" class="figcenter" style="max-width: 14em;"> + <img src="images/i_p088.jpg" width="535" height="855" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 29.</span> + </figcaption> +</figure> + +<p>The receiving telephone somewhat resembles +that of Mr. Bell, yet it presents some differences +which can be understood from the examination of +<a href="#il_29">fig. 29</a>. The magnet <span class="allsmcap">N S</span> is horseshoe in form, +and the magnetising coil <span class="allsmcap">E</span> only covers one of +the poles, <span class="allsmcap">N</span>: this pole is precisely in the centre of +the vibrating plate <span class="allsmcap">L L</span>, while the second pole is +near the edge of this plate. The size of the plate +itself is considerably reduced: its superficies is +about the same as that of a five-franc piece, and it<span class="pagenum" id="Page_89">89</span> +is enclosed in a kind of circular groove, which keeps +it in a definite position. In consequence of this +arrangement the handle of the instrument is of +solid wood, and the vacant space for the electro-magnetic +system is somewhat larger than in the +Bell model; but an arrangement is made for subduing +the echo, and there is a kind of sounding-box +to magnify the sound. It is evident that the relation +which the electro-magnetic system bears to the +vibrating disk must increase the sensitiveness of +the instrument; for as the pole <span class="allsmcap">S</span> is in close contact +with the disk <span class="allsmcap">L L</span>, the latter is polarised, and +becomes more susceptible to the magnetic influence +of the second pole <span class="allsmcap">N</span>, which is separated from it +by an interval not exceeding the thickness of a +sheet of coarse paper. In Mr. Edison’s two +instruments, the receiver and sender, the upper +part <span class="allsmcap">C C</span>, corresponding to the vibrating disk, instead +of being fixed by screws to the handle, is +screwed on to the handle itself, which makes it +much more easy to dismount the instrument.</p> + +<p>Mr. Edison has varied the form of his instruments +in many ways, and their cases have of late +been made of metal with a funnel-shaped mouthpiece +of ebonite.</p> + +<p>When Mr. Edison had ascertained, as indeed +Mr. Elisha Gray had done before him, that induced +currents are more favourable to telephonic +transmissions than voltaic currents, he transformed +the currents from the battery which passed through<span class="pagenum" id="Page_90">90</span> +his sender into induced currents by making them +pass through the primary circuit of a carefully insulated +induction coil; the line wire was then put +into communication with the secondary wire of the +coil. We shall afterwards describe some experiments +which show the advantages of this combination: +for the present we can only point out the fact, +for it is now an integral quality of almost all the +systems of battery telephones.</p> + +<p><i>Edison’s Chemical Telephone.</i>—The curious and +really useful effects produced by Mr. Edison with +his <em>electro-motograph</em> prompted, about the beginning +of the year 1877, his idea of applying the principle of +this instrument to the telephone for the reproduction +of transmitted sounds; and he obtained such +interesting results that the author of an article on +telephones, published in the ‘Telegraphic Journal,’ +August 15, 1877, put forward this invention as one +of the finest of the nineteenth century. It certainly +appears to have given birth to the phonograph, +which has lately become famous, and has so much +astonished men of science.</p> + +<p>To understand the principle of this telephone, +we must give some account of Mr. Edison’s electro-motograph, +discovered in 1872. This instrument +is based upon the principle that if a sheet of paper, +prepared with a solution of hydrate of potash, is +fastened on a metallic plate which is united to the +positive pole of a battery, and if a point of lead +or platinum connected with the negative pole is<span class="pagenum" id="Page_91">91</span> +moved about the paper, the friction which this +point encounters ceases after the passage of the +current, and it is then able to slide as if upon a +mirror until the current is interrupted. Now, as +this reaction may be effected instantaneously under +the influence of extremely weak currents, the +mechanical effects produced by these alternations +of arrest and motion may, by a suitable arrangement +of the instrument, determine vibrations in +correspondence with the interruptions of current +produced by the transmitter.</p> + +<p>In this system the telephonic receiver consists +of a resonator and a drum mounted on an axis and +turned by a winch. A paper band, wound upon a +reel, passes over the drum, of which the surface is +rough, and a point tipped with platinum, and fitted +to the end of a spring which is fixed in the centre +of the resonator, presses strongly on the paper. +The current from the battery, first directed on the +spring, passes by the platinum point through the +chemical paper, and returns by the drum to the +battery. On turning the winch, the paper moves +forward, and the normal friction which is produced +between the paper and the platinum point pushes +the point forward, while producing by means of +the spring a tension on one side of the resonator; +but since the friction ceases at each passage of the +current through the paper, the spring is no longer +drawn out, and the resonator returns to its normal +position. Since this double effect is produced by<span class="pagenum" id="Page_92">92</span> +each vibration made in the sender, a series of +vibrations takes place in the resonator, repeating +those of the sender, and consequently the musical +sounds which affected the sender are reproduced +to a certain extent. According to the American +journals, the results produced by this instrument +are astonishing: the weakest currents, which would +have no effect on an electro-magnet, become perfectly +efficacious in this way. The instrument can +even reproduce with great intensity the highest +notes of the human voice, notes which can hardly +be distinguished by the use of electro-magnets.</p> + +<p>The sender nearly resembles the one we have +previously described, except that, when it is used +for musical sounds, a platinum point is employed +instead of the disk of carbon, and it ought not to +be in constant contact with the vibrating plate. +According to the ‘Telegraphic Journal,’ it consists +simply of a long tube, two inches in diameter, +having one end covered with a diaphragm formed +of a thin sheet of copper, and kept in its place by +an elastic ring. A small platinum disk is riveted +to the centre of the copper diaphragm, and a point +of the same metal, fitted with a firm support, is +adjusted before the disk. When the singer stands +before the diaphragm, its vibration causes it to +touch the platinum point, and produces the number +of breaks in the current which corresponds to the +vibration of the notes uttered.</p> + +<p>The experiments lately made in America, in<span class="pagenum" id="Page_93">93</span> +order to decide on the merits of various telephonic +systems, show that Mr. Edison’s telephone gives +the best results. The ‘Telegraphic Journal,’ May 1, +1878, states that on April 2 Mr. Edison’s carbon +telephone was tested between New York and Philadelphia +on one of the numerous lines of the West +Union. The length of the line was 106 miles, and +ran parallel to other wires almost throughout +its length. The effects of induction caused by +telegraphic transmissions through the adjacent +wires were enough to make speech inaudible +through the other telephones, but they had no +influence on Edison’s telephone, which was worked +with a battery of two cells and a small induction +coil, and Messrs. Batchelor, Phelps, and Edison +were able to converse with ease. Mr. Phelps’ +magnetic telephone, which is considered to be the +most powerful of its kind, did not afford such good +results.</p> + +<p>In the experiments made between the Paris +Exhibition building and Versailles, the jury commission +was able to ascertain that the results were +equally favourable.</p> + +<p><i>Telephones by Colonel Navez.</i>—Colonel Navez +of the Belgian Artillery, inventor of the well-known +balistic chronograph, has endeavoured to improve +the Edison telephone by employing several disks +of carbon instead of one. He considers that the +variations of electric resistance produced by carbon +disks under the influence of unequal pressure depend<span class="pagenum" id="Page_94">94</span> +chiefly on their surface of contact, and he +consequently believes that the more these surfaces +are multiplied, the greater the differences in question +will be, just as it happens when light is polarised +through ice. He adds that these disks act +well by their surfaces of contact, since, if they are +separated by copper disks, the speech reproduced +ceases to be articulate.<a id="FNanchor_6" href="#Footnote_6" class="fnanchor">6</a></p> + +<p>I am not surprised to learn that Colonel Navez +has found a limit to the number of carbon disks, +for the reproduction of speech in this system is +due both to the greatness of the differences of +resistance in the circuit, and to the intensity of +the transmitted current. If therefore the instrument’s +sensitiveness to articulate sounds is increased +by increasing the number of imperfect contacts +in the circuit, the intensity of the transmitted +sounds is diminished, and thus sounds lose their +power. There is consequently a limit to be observed +in the number of carbon disks placed upon +each other; and it depends on the nature of the +imperfect contacts which are employed, and on the +tension of the electric generator.</p> + +<p>In order to stop the unpleasant musical vibrations +which accompany telephonic transmissions, +Colonel Navez employs for the vibrating plate of<span class="pagenum" id="Page_95">95</span> +the sender a silver-plated copper disk, and for +the vibrating plate of the receiver an iron disk +lined with brass and soldered together. He also +employs caoutchouc tubes with mouthpieces and +ear-tubes for the transmission and reception of +sound, and these instruments are placed level on a +table. For this purpose the magnetised bar of the +receiving telephone is replaced by two horizontal +magnets, acting through a pole of the same nature +on a little iron core which carries the coil, and +which is placed vertically between the two magnets.<span class="pagenum" id="Page_96">96</span> +He necessarily makes use of a small Ruhmkorff +coil to transform the electricity of the battery into +induced electricity.</p> + +<figure id="il_30" class="figcenter" style="max-width: 19em;"> + <img src="images/i_p095.jpg" width="758" height="864" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 30.</span> + </figcaption> +</figure> + +<figure id="il_31" class="figcenter" style="max-width: 17em;"> + <img src="images/i_p096.jpg" width="658" height="858" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 31.</span> + </figcaption> +</figure> + +<p><a href="#il_30">Figs. 30</a> and <a href="#il_31">31</a> represent the two parts of this +telephonic system. The carbon battery is in <span class="allsmcap">C</span> +(<a href="#il_30">fig. 30</a>), the vibrating disk in <span class="allsmcap">L L</span>, and the mouthpiece +<span class="allsmcap">E</span>, fitted to a caoutchouc tube <span class="allsmcap">T E</span>, corresponds +at the lower end to the vibrating disk. The carbon +battery is placed in metallic contact with the circuit +by a platinum rod <span class="allsmcap">E C</span>, and the vibrating disk +also communicates with the circuit through a binding-screw.<span class="pagenum" id="Page_97">97</span> +In the receiving telephone (<a href="#il_31">fig. 31</a>) the +upper part is arranged much as in the ordinary +telephones, except that, instead of a mouthpiece, +the instrument is fitted with an ear-tube <span class="allsmcap">T O</span>. The +two horseshoe magnets, <span class="allsmcap">A</span>, <span class="allsmcap">A</span>, which communicate a +uniform polarity to the iron core <span class="allsmcap">N</span>, support the +induction coil <span class="allsmcap">B</span>. The two terminals of this +receiver are connected with the supplementary +wire of the induction coil, and the two terminals of +the sender are connected with the two ends of +the primary of this coil, and with the battery which +is inserted in the circuit near this instrument.</p> + +<p><i>The Pollard and Garnier Telephones.</i>—The +battery telephone made by MM. Pollard and +Garnier differs from the foregoing in this particular: +it simply employs two points of graphite, mounted +in metallic porte-crayons, and these points are +directly applied against the vibrating plate with a +pressure which must be regulated. <a href="#il_32">Fig. 32</a> represents +the arrangement adopted, which, however, +may be infinitely varied.</p> + +<p><span class="allsmcap">L L</span> is the vibrating tin plate, above which is the +mouthpiece <span class="allsmcap">E</span>, and <span class="allsmcap">P</span>, <span class="allsmcap">P′</span> are the two graphite points +with their porte-crayons. There is a screw on the +lower part of the porte-crayons which is fixed in a +hole pierced in a metallic plate <span class="allsmcap">C C</span>, and by this +means the pressure of the pencils against the disk +<span class="allsmcap">L L</span> can be regulated. The metallic plate <span class="allsmcap">C C</span> is +made in two pieces, placed side by side, but +insulated from each other, so that they may be placed<span class="pagenum" id="Page_98">98</span> +in communication with a cylindrical commutator, +and by its means the circuit can be arranged in +different ways. Since the commutator consists of +five sheets, the transition from one combination to +another is instantaneous, and these combinations +are as follows:</p> + +<p>1. The current enters by the pencil <span class="allsmcap">P</span>, passes +into the plate, and so to line.</p> + +<p>2. The current enters by the pencil <span class="allsmcap">P′</span>, passes +into the plate, and so to line.</p> + +<p>3. The current comes simultaneously by the two +pencils <span class="allsmcap">P</span> and <span class="allsmcap">P′</span>, goes into the plate, and thence to +line.</p> + +<p>4. The current comes by the pencil <span class="allsmcap">P</span>, goes +thence to the plate, then into the pencil <span class="allsmcap">P′</span>, and so +to line.</p> + +<figure id="il_32" class="figcenter" style="max-width: 12em;"> + <img src="images/i_p098.jpg" width="459" height="305" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 32.</span> + </figcaption> +</figure> + +<p>By this means there are two elements of combination, +which may be employed separately, or by +coupling them for tension or quantity.</p> + +<p>When the pencils are properly regulated and +give a regular transmission of equal intensity, the +effects produced in the transition from one combination<span class="pagenum" id="Page_99">99</span> +to another may be easily studied, and it has +been ascertained: first, that in a short circuit there +is no appreciable change, whatever be the combination +employed; secondly, that when the circuit +is long, or of great resistance, the tension arrangement +is the best, and this in proportion to the length +of the line.</p> + +<p>This telephonic system, like the two preceding +ones, requires an inducing machine to transform +voltaic into induced currents: we shall presently +speak of this important accessory of these instruments.</p> + +<p>Besides this arrangement, MM. Pollard and +Garnier have employed the one we have represented +in <a href="#il_5">fig. 5</a>, which has given better results. We shall +see presently that it can be used as the receiving +organ of sounds. In each case the two carbons +must be placed in contact, and subjected to a +certain initial pressure, which should be regulated +by the screw fitted to the support of the lower +carbon.</p> + +<p>As for the receiving telephone, the arrangement +adopted by MM. Pollard and Garnier is the same +as Bell’s, except that they employ tin plates and +helices of greater resistance. This resistance ranges +in fact from 100 to 125 miles. ‘We have always +held,’ these gentlemen say, ‘that whatever may +be the resistance of the outer circuit, there is an +advantage in increasing the number of spirals,<span class="pagenum" id="Page_100">100</span> +even when using wire No. 42, which is the one we +prefer.’</p> + +<figure id="il_33" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p100.jpg" width="901" height="690" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 33.</span> + </figcaption> +</figure> + +<p><i>M. Hellesen’s Reaction Telephone.</i>—M. Hellesen +believed that the vibrations produced by the voice +on the carbon of a telephonic sender would be +magnified if the moveable part of the rheotome +were subjected to an electro-magnetic action resulting +from the vibrations themselves, and he has +contrived a sender, which is based on the principle +shown in <a href="#il_33">fig. 33</a>, and which has the merit of forming +in itself the inducing apparatus intended to transform +the voltaic currents employed. This instrument is +composed of a vertical iron tube, supported on a +magnetic bar <span class="allsmcap">N S</span>, and surrounded by a magnetising<span class="pagenum" id="Page_101">101</span> +coil <span class="allsmcap">B B</span>, above which is fixed an inducing +helix of fine wire <span class="allsmcap">I I</span>, communicating with +the circuit. Within the tube there is a lead pencil +<span class="allsmcap">C</span>, held by a porte-crayon which can be raised or +lowered by means of a screw <span class="allsmcap">V</span> fixed below the +magnetic bar. Finally, above this pencil, there is +an iron vibrating plate <span class="allsmcap">L L</span>, with a platinum point +in communication with the battery in its centre; +the local circuit communicates with the pencil by +means of the magnetising helix <span class="allsmcap">B</span>, and for this +purpose one end is soldered to the iron tube.</p> + +<p>From this arrangement it follows that the +vibrations of the plate <span class="allsmcap">L L</span>, at the moment when it +comes nearest to the pencil, tend to become greater +in consequence of the attractive force exerted on +the plate, and as the pressure of the lead pencil is +increased, it increases the differences of resistance +which result from it, and consequently causes +greater variations in the intensity of the transmitted +currents.</p> + +<p><i>Reaction Telephone of Messrs. Thomson and +Houston.</i>—The telephonic arrangement we have +described has lately been adopted by Mr. Elihu +Thomson and Mr. Edwin J. Houston, who, on +June 21, 1878, two months after M. Hellesen explained +his system to me,<a id="FNanchor_7" href="#Footnote_7" class="fnanchor">7</a> published an article in +‘The English Mechanic and World of Science’<span class="pagenum" id="Page_102">102</span> +about an instrument very similar to that of M. +Hellesen.</p> + +<p>In their instrument, the current, which passes +through a body of moderately conducting capacity, +acts on an electro-magnet provided with an induction +coil, and this electro-magnet reacts on the +diaphragm, in order to increase the range of its +vibrations, and to create at the same moment two +electric actions in the same direction: the only +difference lies in the arrangement of the contact of +this indifferent conductor with the vibrating plate. +Instead of a simple contact effected by pressure +between this plate and a carbon pencil, a fragment of +the same substance with a sharpened point is fixed +on the vibrating plate, and it dips into a drop of +mercury which has been poured into the receptacle +made for it at the upper end of the electro-magnet. +In other respects, the arrangement of the instrument +is that of an ordinary telephone, and the iron rod +of the electro-magnet represents the magnetised +bar of the Bell telephone. The inventors assert +that this instrument can be used both as a sender +and receiver, and it is in the following manner +that it is worked in each case.</p> + +<p>When the instrument is transmitting, the morsel +of carbon dips more or less into the mercury, and +consequently differences are produced in the surfaces +of contact, according to the range of vibrations +made by the plate; the current varies in +intensity in proportion to this range, and induced<span class="pagenum" id="Page_103">103</span> +currents in the induction coil result from these variations; +the induced currents react on the receiving +telephone, as in Bell’s instrument, and are further +strengthened by those which are produced electrically +by the movement of the diaphragm before +the induction coil, and the iron of the electro-magnet.</p> + +<p>When the instrument is used as a receiver, the +usual effects are displayed, for since the iron of the +electro-magnet is magnetised by the current, its +conditions are precisely those of the ordinary Bell +telephone, and the induced currents reach it in the +same manner, only with greater intensity. Messrs. +Thomson and Houston assert that their system has +produced excellent results, and that by it the sound +of the voice is much less altered than in other +telephones.</p> + +<p><i>Telephones with batteries and liquid senders.</i>—We +have seen that in 1867 Mr. Gray conceived +the idea of a telephonic system based on the +differences of resistance effected in a circuit completed +by a liquid, when the layer of liquid interposed +between the electrodes varies in thickness +under the influence of the vibrations of the telephonic +plate which is in communication with one +of these electrodes. This system has since been the +subject of study by several inventors, among others +by MM. Richemond and Salet; and I give some of +the accounts which have been published respecting +their researches.</p> + +<p><span class="pagenum" id="Page_104">104</span></p> + +<p>Another telephone for the reproduction of +articulate sounds, which M. Richemond terms the +<em>electro-hydro telephone</em>, has been recently patented +in the United States. It resembles that of Mr. +Edison in some respects, but instead of making use +of carbon disks to modify the resistance of the +circuit, water is employed, and this water is placed +in communication with the circuit and battery by +means of two platinum points, one of which is fixed +on the metallic diaphragm which vibrates under the +influence of the voice. As the vibrations of the diaphragm +transport the point which is attached to it to +different parts of the interpolar layer of liquid, they +diminish or increase the electric resistance of this +layer, and cause corresponding variations in the +intensity of the current traversing the circuit. The +receiving telephone is of the usual kind. (See +‘Telegraphic Journal,’ September 15, 1877.)</p> + +<p>M. Salet writes: ‘I thought it would be interesting +to construct a telephone in which there +should be absolute solidarity in the movements +of the two membranes, and for this purpose I +have availed myself of the great resistance of +liquids. Mr. Bell had already obtained some +results by attaching to the vibrating membrane a +platinum wire communicating with a battery, and +dipping more or less into a metallic vessel, itself +connected by the line with the receiving telephone +and containing some acidulated water. I have substituted +for the platinum wire a small aluminium<span class="pagenum" id="Page_105">105</span> +lever supporting a disk of platinum, and at a very +slight distance from it there is a second disk in connection +with the line. The vibrations of the membrane, +tripled or quadrupled in their range, are not +altered in form, thanks to the small size and light +weight of the lever: they cause variations in the +thickness of the liquid layer traversed by the +current, and consequently in its intensity, and these +variations cause corresponding differences in the +attractive force of the receiving electro-magnet. +Under its influence the receiving membrane executes +movements which are identical with those of +the sending membrane. The sound transmitted +is very distinct, and its <em>timbre</em> is perfectly maintained, +a result which might have been anticipated. +The consonants, however, are not so clearly pronounced +as those transmitted by Mr. Bell’s instrument. +This inconvenience is most apparent when +the lever is heavy, and might easily be obviated. +The electrolysis also produces a continual murmur, +but this does not interfere with the distinctness of +the sound.</p> + +<p>‘Since on this system the voice is not required +to <em>produce</em>, but only to <em>direct</em> the electric current +generated by a battery, the intensity of the sound +received might in theory be increased at pleasure. +I have in fact been able to make the receiver emit +very powerful sounds, and I think that this advantage +greatly counterbalances the necessity of employing +a battery, and a somewhat delicate sending<span class="pagenum" id="Page_106">106</span> +instrument. Unfortunately it can only be +used for moderate distances. Assuming that any +displacement of the transmitting membrane increases +the resistance to a degree equivalent to +five or six hundred yards of wire: if the line is five +hundred yards long, the intensity of the current +will be reduced by one half, and the receiving +membrane will take up a fresh position, considerably +differing from the first; but if the line is three +hundred miles in length, the intensity of the current +will only be modified by a thousandth part. An +immense battery must therefore be employed in +order that this variation may be translated by a +sensible change in the position of the receiving +membrane.’ (See ‘Comptes Rendus de l’Académie +des Sciences,’ February 18, 1878.)</p> + +<p>M. J. Luvini, in an article inserted in ‘Les +Mondes,’ March 7, 1878, has suggested a system +of rheotome by means of a current, for battery +telephones, which, although complicated, possibly +offers some advantages, since it produces currents +alternately reversed. In this system, the vibrating +disk of the sender, which should be in a vertical +position, reacts on a moveable horizontal wire, +turned back at a right angle, and supporting on +each of its branches two platinum points which +dip into two bulbs, filled with a liquid of moderate +conducting capacity. The two branches of this +wire, insulated from each other, are placed in communication +with the two poles of the battery, and<span class="pagenum" id="Page_107">107</span> +the four cups into which the platinum wire dips +communicate inversely with the line and the +earth by means of platinum wires immoveably +fixed in the cups. It follows from this arrangement, +that when the distances are duly regulated +between the fixed and moveable wires, two equal +currents will be opposed to each other across +the line circuit when the diaphragm is motionless; +but as soon as it vibrates, the respective +distances of the wires will vary, and it follows from +this that there will be a differential current, of which +the intensity will correspond with the extent of the +displacement of the system, or with the range of +vibrations, and the direction will vary with the +movements above or below the line of the nodes of +vibration. In this way the advantage of the induced +currents is obtained.</p> + +<p><i>Telephones with a battery and voltaic arcs.</i>—In +order to obtain variations of resistance of still +greater sensitiveness than is the case with liquids +or pulverised substances, the idea has been suggested +of employing conductors of heated gas, +and several arrangements of battery telephones +have been made in which the circuit was completed +by a stratum of air, separating the vibrating disk +from a platinum point, which serves to excite an +electric discharge of high tension. Under these +conditions, the stratum of air becomes the conductor, +and the intensity of the current which +traverses it corresponds to its thickness. This<span class="pagenum" id="Page_108">108</span> +problem has been solved, either by means of +voltaic currents of high tension, or by a Ruhmkorff +coil.</p> + +<p>The former system was arranged by M. Trouvé, +and he writes as follows on the subject in the +journal ‘La Nature’ of April 6, 1878: ‘A metallic +vibrating membrane forms one of the poles of a +high tension battery; the other pole is fastened +before the disk by a micrometer screw which can +be adjusted so as to vary the distance from the disk +according to the tension of the battery, but without +ever coming in contact with it. The distance +must not in any case exceed that to which the +discharge of the battery can extend. Under these +conditions, the membrane which vibrates under the +influence of the waves of sound has the effect of +constantly modifying the distance between the +two poles, and thus of continually varying the intensity +of the current: consequently the receiving +instrument (a Bell telephone, or telephone with an +electro-magnet) is subjected to magnetic variations, +corresponding to the variations of the current which +affect it, and this has the effect of making the +receiving instrument vibrate at the same moment. +This kind of telephonic instrument relies, therefore, +on the possibility of varying within wide limits the +resistance of the outer circuit of a high-tension +battery, in which the poles are not in contact. In +order to vary the conditions of this resistance, it is +also possible to interpose some vapour or other<span class="pagenum" id="Page_109">109</span> +medium, such as air, or gas of greater or less +rarity.’</p> + +<p>M. Trouvé thinks that he was successful with +his battery of small disks, moistened with sulphate +of copper and sulphate of zinc, arranging these +elements, to the number of five or six hundred, in +glass tubes of small diameter. It is well known +that it is unnecessary for the elements to be of +large size in order to obtain tension currents.</p> + +<p>M. de Lalagade has suggested an analogous +mode by employing for the formation of the arc +a current of which the tension is increased by inserting +a strong electro-magnet into the circuit. +This electro-magnet acts on a Hughes magnet in +order to produce induction currents capable of +making the receiving instrument act. M. de +Lalagade says that a Bunsen battery, or one of six +cells with bichromate of potash, will be enough +to produce a continuous voltaic arc between the +vibrating plate of a telephone and a platinum +point which is sufficiently remote to avoid contact. +It is necessary, however, to begin with a contact, in +order to produce the formation of this arc. In M. +de Lalagade’s system, the vibrating plate should +have in its centre a small platinum plate, in order +to obviate the oxidising effects of the spark. The +inventor asserts that sounds transmitted in this +way, and reproduced in a telephone of which the +electro-magnetic system is set upon a sounding-box, +will have greater intensity than the sounds<span class="pagenum" id="Page_110">110</span> +transmitted by an ordinary telephone, and the +speaker will appear to be close to the ear.</p> + +<p><i>Mercury Telephones.</i>—These systems are based +on the physical principle discovered by M. Lippmann, +that if a layer of acidulated water is placed above +mercury, and connected with it by an electrode +and wire, every mechanical action which exerts +pressure on the surface of the mercury, and alters +the form of its meniscus, will cause an electric +reaction, capable of producing a current with a +force which corresponds to the mechanical action +exerted. Conversely, every electric action produced +on the circuit of such a system will occasion +a displacement of the meniscus, and consequently +its movement, which will be more marked in proportion +to the smallness of the tube in which the +mercury is placed, and to the greatness of the +electric action. This electric action may result +from a difference of potential in the electric condition +of the two extremities of the circuit, which +communicate with the electric source employed, or +with some electric generator.<a id="FNanchor_8" href="#Footnote_8" class="fnanchor">8</a></p> + +<p><span class="pagenum" id="Page_111">111</span></p> + +<figure id="il_34" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p111.jpg" width="933" height="535" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 34.</span> + </figcaption> +</figure> + +<p>In accordance with these effects, it is intelligible +that if two tubes <span class="allsmcap">T</span> <span class="allsmcap">T</span>, pointed at the end, and containing +mercury, are plunged into two vessels <span class="allsmcap">V</span> <span class="allsmcap">V</span> +(<a href="#il_34">fig. 34</a>) containing acidulated water and mercury, +and metallic wires, <span class="allsmcap">P P</span>, <span class="allsmcap">Q Q</span>, are used, first to connect +the columns of mercury in the tubes, and secondly +the layers of mercury at the bottom of the two vessels, +the tubes being a little removed from the surface of +the mercury in the vessels, we shall then have a +metallic circuit, completed by two electrolytes, +one of which will be subjected to the mechanical +or electrical effects produced in the other. If two +vibratory plates <span class="allsmcap">B</span> <span class="allsmcap">B</span> are placed above the tubes, +and one of these is caused to vibrate, the other +will reproduce these vibrations, influenced by the +vibratory movements communicated by the corresponding<span class="pagenum" id="Page_112">112</span> +column of mercury. The vibrations +themselves will be in connection with the electrical +discharges resulting from the movements of the +column of mercury in the first tube, which are +mechanically produced. If an electric generator is +introduced into the circuit, the effect which we +have just analysed will be caused by modifications +in the potential of this generator, in consequence +of electro-capillary effects. But if no generator +is employed, the action will result from electric +currents determined by the electro-capillary attraction +itself. In the latter case, however, the instrument +must be more delicately made, in order to +obtain more sensitive electric reaction, and M. A. +Bréguet describes his instrument as follows.</p> + +<p>‘The instrument consists of a tube of thin +glass, a few centimètres in length, containing alternate +drops of mercury and acidulated water, so as to +constitute so many electro-capillary elements, connected +in tension. The two ends of the tube are +fused together, yet so as to allow a platinum wire +to touch the nearest drop of mercury on each side. +A small circle of thin deal is fixed at right angles to +the tube by its centre, thus providing a surface of +some extent, which can be applied to the ear when +the instrument is a receiver, and to make the tube +more mobile under the influence of the voice +when the instrument is a sender. The following +are the advantages offered by instruments of this +<span class="locked">construction:—</span></p> + +<p><span class="pagenum" id="Page_113">113</span></p> + +<p>‘1. They do not involve the use of a battery.</p> + +<p>‘2. The disturbing influence of the resistance of +a long line is almost destroyed in these instruments, +although it is still appreciable in the Bell +telephone.</p> + +<p>‘3. Two mercury telephones, coupled together +as we described above, are absolutely correlative, +in this sense, that even different positions in the +equilibrium of the mercury in one of them produce +different positions of equilibrium in the +opposite instrument. It is therefore possible to +reproduce at a distance, without a battery, not +merely faithful indications of oscillatory movements, +which is done by the Bell telephone, but +also the exact image of the most general movements.’</p> + +<p><i>Friction Telephones.</i>—Mr. E. Gray has quite +recently applied the principle of producing sounds +by the friction of animal tissues to the construction +of a speaking telephone which may be heard +through a whole room, like the singing condenser. +He obtains this result by means of clockwork, +which causes the rotation of the metallic disk of +which we have spoken (p. 23), and on which a piece +of skin is so arranged as to produce friction. A +carbon or liquid telephone is placed at the sending +station, in such a way as to react on an induction +coil, as in the systems of Edison, Navez, or +Pollard, and speech is reproduced on the rotating +disk, and is audible, as we have said, without<span class="pagenum" id="Page_114">114</span> +the necessity of approaching the ear to the instrument.</p> + +<p>The best arrangement of the metallic disk on +which the animal tissue rubs is that of a cylindrical +box, of which the outer lid is made of a thin sheet +of zinc with a highly polished, slightly oxidised +surface; for the agent of friction, glove-leather +slightly moistened with acidulated water may be +used, or a sinew of an ox, or skin taken from the +ear or tail of a pig.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="MODIFICATIONS_INTRODUCED_IN_THE_CONSTRUCTION"><span id="toclink_114"></span>MODIFICATIONS INTRODUCED IN THE CONSTRUCTION +OF THE BELL TELEPHONES.</h2> +</div> + +<p>The modifications which we have been considering +relate to the principle of the instrument; +those which we have now to consider are only +modifications in the form and arrangement of the +different organs which form the Bell telephone +itself, and which have been designed with the +object of increasing the intensity and distinctness +of the sounds produced.</p> + +<p><i>Telephones with several diaphragms.</i>—When we +remember that the induced currents caused in a +magnet result from the vibratory movements of +the diaphragm, and that these are produced by the +vibrations of the stratum of air interposed between +this diaphragm and the vocal organ, it necessarily +follows that if these vibrations of the air react on +several diaphragms, each attached to its electro-magnetic +organ, several induced currents might be<span class="pagenum" id="Page_115">115</span> +caused simultaneously, and if these were properly +connected, their effects on the receiver would be +so much the more intense, since the sounds produced +would result from the combination of +several sources of sound. Several inventors, starting +from this argument, have planned instruments +of varying ingenuity, which we will now describe, +but without being able to declare who was the +first to realise this idea. It is in fact so simple, +that it probably suggested itself to the minds +of several inventors at the same time, and we see +that while M. Trouvé proposed this improvement +in France in November 1877, it was tried +in America and discussed in England, where +indeed it was not expected to produce very +favourable results. Mr. Preece wrote on the subject +in a paper entitled ‘On some Physical Points connected +with the Telephone,’ which was published in +April 1878. He observes that all the attempts +to improve the telephone have ended in disappointment +and failure. One of the first attempts +of the kind was made by Mr. Wilmot, who expected +to obtain favourable results by augmenting +the number of diaphragms, helices, and magnets, +connecting the helices in a series, and causing them +to act simultaneously, so as to increase the energy +of the currents developed by the influence of the +voice; but experience showed that when the instrument +acted directly, the vibratory effect of +each of the diaphragms decreased in proportion to<span class="pagenum" id="Page_116">116</span> +their number, and the general effect remained the +same as with a single diaphragm. Mr. Wilmot’s +instrument was made in the beginning of October +1877, and that of M. Trouvé was only an imitation +of it.</p> + +<p>On the other hand, we see that if the telephones +with several membranes were not successful in +England, this was not the case in America, for the +telephones which experience has shown to give the +best results in that country are those of Mr. Elisha +Gray and Mr. Phelps, and these have several diaphragms. +It is evident that there are details of construction +in these instruments which may appear +insignificant in theory, and which are notwithstanding +very important from a practical point of +view, and we believe that it is to this circumstance +that instruments of this kind owe their success or +failure. Thus, for example, it seems that the +vibrations of air caused in the mouthpiece ought to +be immediately directed on the surface of the diaphragms +by means of distinct channels; it is +necessary that the empty space round each diaphragm +should be sufficiently limited to prevent +echoes and interruptions, unless the case is so large +that there is no danger of such effects. Above all, it +is necessary that the organs should be fixed in some +material unsusceptible of reverberation, and for this +reason a preference is given to iron or ebonite. It is +certain that when the instrument is properly made, +its effects are superior to those of the Bell telephones,<span class="pagenum" id="Page_117">117</span> +and it is asserted in the ‘Telegraphic Journal’ that +experiments were made with one of these instruments +before the Royal Society, in London, May +1, 1878, and that the intensity of sound was in +proportion to the number of diaphragms. This +instrument was designed by Mr. Cox Walker, of +York, and possessed eight diaphragms. He considers +that this is the arrangement which gives the +best results.</p> + +<figure id="il_35" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p117.jpg" width="761" height="987" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 35.</span> + </figcaption> +</figure> + +<p><span class="pagenum" id="Page_118">118</span></p> + +<p><i>Mr. Elisha Gray’s System.</i>—Mr. Elisha Gray’s +last system, which we represent in <a href="#il_35">fig. 35</a>, is one +of those which have given the best effects. It +is made, as we see, of two telephones, side by side, +to which correspond two tubes, issuing from a common +mouthpiece <span class="allsmcap">E</span>. One of these telephones is seen +in section in the plate, the other in elevation, and +they correspond to the two branches of a nickel-plated +horseshoe magnet <span class="allsmcap">N U S</span>, which may serve as +a suspension ring. In that part of the plate which +represents the section, the induction coil is shown +in <span class="allsmcap">B</span>, and the magnetic core, of soft iron, in <span class="allsmcap">A</span>, +which is screwed to the polar end of the magnet <span class="allsmcap">S</span>; +the vibrating plate is in <span class="allsmcap">L L</span>, and, as we see, the +tube of the mouthpiece terminates on its surface.</p> + +<p>In another model there are four telephones side +by side, instead of two, and the effects produced +are still more marked.</p> + +<p><i>Mr. Phelps’s System.</i>—This system is only deduced +from the last, but there are two models of it. +In the larger one, which makes it possible to hear +as distinctly as if the person with whom conversation +is held were speaking in a loud voice in the +same room, the two telephones are placed parallel +to each other, and so as to present their diaphragms +vertically; the space between these two diaphragms +is occupied by a vertical tube, terminating at its +lower end in a horizontal tube corresponding to +the centres of the two diaphragms, and on this +tube the mouthpiece is fitted, which projects outside<span class="pagenum" id="Page_119">119</span> +the box in which the instrument is enclosed. +The induction coils, and the magnetic cores which +traverse them, follow the axis of the system, and +seem to constitute the axis of a wheel which +is polarised by the poles of a horseshoe magnet, +of which the position with reference to the surface +of the diaphragms can be regulated by moveable +screws. The appearance of the instrument somewhat +resembles a gyroscope, resting by a horizontal +axis on two shafts which issue from a flattened +horseshoe magnet.</p> + +<p>Above this system there is the electro-magnetic +apparatus of the call-bell, in which there is nothing +peculiar, and which is like the German +alarums of which we shall speak at the end of this +account. This instrument is remarkable for strength +and clearness of sound, and especially for its freedom +from the Punch and Judy voice so displeasing +in other telephones.</p> + +<p>Mr. Phelps’s small model is in the form of an +oblong or elliptical snuff-box, of which the two +centres are occupied by two telephonic systems, +influenced by the same magnet. This magnet is +placed in a horizontal position below the snuff-box, +and its poles correspond to the magnetic cores of +the coils. These cores are made of iron tubes, +split longitudinally in order to destroy irregular +induction reactions, and the iron diaphragms rest on +five spiral springs, which raise them above the +magnetic system. On their other surface the diaphragms<span class="pagenum" id="Page_120">120</span> +are provided with rings of some semi-elastic +substance, which prevent the central vibrations +of the disks from becoming complicated by +those of their edges. The lid, hollowed out in +very shallow cavities, is next placed upon the disks, +and there are channels of communication in it to +serve as a sounding-box. The mouthpiece corresponds +to one of these cavities, and the other is closed +by a small metallic stopper, which can be withdrawn +to regulate the instrument when necessary. +Since the vibrations of air are transmitted by the +channels to both cavities, the two telephones act +together, although at first sight only one of them +seems to be required to produce the effect.</p> + +<p>Mr. Phelps praises the simultaneous effects produced +on the two instruments, which he ascribes, +first, to the semi-elastic ring surrounding the rim of +each disk, and acting as the hammer of the ear, +that is, as a damper; then, to the longitudinal splits +of the magnetic core, and lastly to the small size of +the cavities left above the vibrating disks. The +instrument is made of ebonite, grooved on the +surface in order to give a better grasp to the +hand.</p> + +<p>Mr. Phelps has a new model, called <em>the crown +telephone</em>, which is now in use in America, together +with Mr. Edison’s carbon sender. In it each of +the two systems of the large model we have +described is worked by six horseshoe magnets +radiating round the magnetic core, and so arranged<span class="pagenum" id="Page_121">121</span> +that the north poles correspond to this core, and +the other poles to the circular rim of the diaphragm. +In this way the magnetic field is considerably +enlarged, and the sound much intensified.</p> + +<p>In experiments recently made at Dr. Wells’s +church, New York, an assembly of three hundred +people were able to hear speech and vocal or +instrumental music distinctly in different parts of +the hall.</p> + +<p><i>Mr. Cox Walker’s System.</i>—This system, on +which we have already said a few words, has +exactly the arrangement of that by Mr. Elisha +Gray. The magnets which act upon the diaphragms +are horseshoe, and separate pipes, issuing from a +common mouthpiece, direct the vibrations of air +on the diaphragms. These, indeed, are only +defined parts of one diaphragm, bounded in a circle +by mouthpieces corresponding to the air-pipes, and +sufficiently restricted on their edges to limit the +field of vibration.</p> + +<p><i>M. Trouvé’s System.</i>—M. Trouvé has simplified +the arrangement of telephones with a double +diaphragm, by designing the instrument so as to +make Bell’s bar magnet react by both poles at +once on several disks. For this purpose, he +employs a tubular magnet, and winds a helix +throughout its whole length, as we see in <a href="#il_36">fig. 36</a>. +This magnet is maintained in a fixed position in +the centre of a small cylindrical box, of which the +base is slightly funnel-shaped, thus acting as a<span class="pagenum" id="Page_122">122</span> +mouthpiece and acoustic tube. It is consequently +pierced in the centre with a hole larger at <i>a</i>, the +station for speaking, than on the opposite side <i>b</i>. +Between the base and the poles of the magnet +there are two vibrating iron plates, <span class="allsmcap">M</span>, <span class="allsmcap">M′</span>, one of +which, <span class="allsmcap">M</span>, is pierced with a hole <i>a</i> of the same +diameter as the hollow part of the magnet, and +consequently smaller than that of the mouthpiece. +Finally, several other plates <i>n</i>, <i>n</i>, <i>n</i>, are ranged in +parallel lines between these two plates, so that the +magnet and its helix may pass through them.</p> + +<figure id="il_36" class="figcenter" style="max-width: 18em;"> + <img src="images/i_p122.jpg" width="697" height="505" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 36.</span> + </figcaption> +</figure> + +<p>When anything is said before the mouthpiece +<i>a</i>, the waves of sound encountering the edges of +the plate <span class="allsmcap">M</span> place it in vibration, and, continuing +their passage inside the tubular magnet, they cause +the plate <span class="allsmcap">M</span>′ to vibrate at the same time as <span class="allsmcap">M</span>. A +double inducing action therefore takes place on the<span class="pagenum" id="Page_123">123</span> +tubular magnet, and this is translated by the +induced currents developed in the helix, which +have greater energy since each of the plates intensifies +the magnetic effects produced at the pole +opposite to the one they influence, which is always +the case with bar magnets when the inactive pole +is provided with an armature. This advantage +may even be obtained in the case of ordinary +telephones, if the screw which holds the magnet is +placed in contact with a mass of soft iron.</p> + +<p>In M. Trouvé’s arrangement, the induced +currents therefore possess greater energy; but he +adds that the sounds reproduced will also be +strengthened by the multiplicity of vibratory +effects, and by the enlargement of the magnetic +effects, which results from a better arrangement of +the magnets.</p> + +<p>‘When the ear is placed at <i>a</i>,’ M. Trouvé writes, +‘it perceives immediately the sounds produced by +the first plate <span class="allsmcap">M</span>, and those of the second plate +reach the ear through the interior of the magnet. +This new arrangement is well adapted for an +experimental comparison of the results produced +by a telephone with a single membrane (a Bell +telephone), and those produced by a telephone with +several membranes. It is in fact enough to listen at +the two faces of the telephone alternately, in order +to perceive at once the difference of intensity in +the sounds produced. Those collected at <i>a</i>, on +the side of the pierced iron plate, appear manifestly<span class="pagenum" id="Page_124">124</span> +doubled in intensity compared with those +collected at <i>b</i> on the side of the simple membrane +which forms the ordinary telephone.</p> + +<p>‘The difference is still more striking if, in +transmitting or receiving a sound of invariable +intensity through a multiple telephone, the unbroken +membrane <span class="allsmcap">M′</span> is repeatedly prevented from +vibrating.’</p> + +<p>Before making this arrangement M. Trouvé had +planned another, which he presented to the Académie +des Sciences, November 26, 1877, and which +we have glanced at in the beginning of this chapter. +He describes it in these <span class="locked">terms:—</span></p> + +<p>‘In order to increase the intensity of the effects +produced in the Bell telephone, I have substituted +for the single membrane a cubic chamber, of which +each face is, with one exception, formed of a vibrating +membrane. Each of these membranes, put in +vibration by the same sound, influences a fixed magnet, +which is also provided with an electric circuit. +In this way, by connecting all the currents generated +by the magnets, a single intensity is obtained, +which increases in proportion to the number of magnets +influenced. The cube might be replaced by a +polyhedron, of which the faces might be formed of +an indefinite number of vibrating membranes, so as +to obtain the desired intensity.’</p> + +<p><i>M. Demoget’s System.</i>—Several other systems of +telephones with multiple membranes have been +proposed. One of them, planned by M. Demoget,<span class="pagenum" id="Page_125">125</span> +consists in placing before the vibrating disk of the +ordinary Bell telephone, separated by the space of +a millimètre, one or two similar vibrating disks, +taking care to pierce in the centre of the first a +circular hole of the same diameter as that of the bar +magnet, and to pierce a larger hole in the second +membrane. The inventor asserts that the distinctness +as well as the intensity of sounds is increased +in this way.</p> + +<p>‘By this arrangement,’ says M. Demoget, ‘since +the vibrating magnetic mass is larger in proportion +to the magnet, the electro-motive force of the +currents generated is increased, and consequently +the vibrations of the disks of the second telephone +are more perceptible.’</p> + +<p><i>Mr. McTighe’s Telephone.</i>—In this telephone, +which has several diaphragms, there is a horseshoe +magnet, and instead of placing the coils upon the +poles, there is a single coil fastened to an iron +core, which is inserted between wide polar appendices +fitted to the two poles of the magnet. These +appendices consist of thin plates, which act as +vibrating plates.</p> + +<p><i>Modifications in the arrangement of Telephonic +Organs.</i>—We see that the forms given to the Bell +telephone are very varied, and this is still more +the case with its constituent organs, without, however, +producing any remarkable improvements. +Mr. Preece observes that little has been gained by +varying the size and strength of the magnets, and<span class="pagenum" id="Page_126">126</span> +the best effects have been obtained by using the +horseshoe magnets directed by Mr. Bell himself. +The telephone was certainly introduced into Europe +with the arrangement which is theoretically the +best, although Mr. Bell is still occupied in improving +it. This is also the opinion of M. Hellesen, who, +like Mr. Preece, has made many experiments on +this point; but this has not deterred several +people from declaring that they have discovered +the way of making a telephone speak so as to be +audible to an assembly of people.</p> + +<p>Of the different instruments made with this object, +that of M. Righi seems to be the most important. +It was lately tried with success at the Académie +des Sciences, the Conservatoire des Arts et Métiers, +and the Press pavilion of the Exhibition.</p> + +<figure id="il_37" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p127.jpg" width="770" height="803" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 37.</span> + </figcaption> +</figure> + +<p>The receiver is only a Bell telephone of large +size, with a diaphragm of parchment <span class="allsmcap">L L</span> (<a href="#il_37">fig. 37</a>), +in the centre of which there is a sheet-iron disk <span class="allsmcap">F</span>. +This membrane is stretched on a large funnel <span class="allsmcap">E</span>, +which is fixed on a box <span class="allsmcap">C C</span>, containing the electro-magnetic +coil <span class="allsmcap">B</span>: and the magnet <span class="allsmcap">N S</span>, much larger +than in the ordinary instruments, issues from the +box, and serves as its support.</p> + +<figure id="il_38" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p127b.jpg" width="902" height="515" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 38.</span> + </figcaption> +</figure> + +<p>The sender resembles the one represented +in <a href="#il_19">fig. 19</a>, except that, instead of liquid, M. Righi +employs plumbago mixed with powdered silver, +and the platinum needle is replaced by a metallic +disk <span class="allsmcap">D</span> (<a href="#il_38">fig. 38</a>). The receiver <span class="allsmcap">I</span>, which contains the +powder, is supported on a spring <span class="allsmcap">R</span>, which can be<span class="pagenum" id="Page_128">128</span> +pushed up and down by a regulating screw <span class="allsmcap">V</span>, and +the whole is fitted into a box <span class="allsmcap">C C</span>, and supported +on a foot <span class="allsmcap">P</span>. The speaker places himself above +the mouthpiece <span class="allsmcap">E</span>, and the vibrations transmitted +to the membrane <span class="allsmcap">L L</span> cause the variations of resistance +in <span class="allsmcap">I</span> which are necessary for the transmission +of speech, as in the Edison system. Two +Bunsen cells are enough to set the instrument +at work, and it will make the sound of a trumpet +or flute audible throughout a room. Vocal music, +which is less intense, is necessarily transmitted to +a rather less distance, and words spoken in the +natural voice are heard by those standing about +two yards and a half from the instrument.</p> + +<p>The maximum distance at which the instrument +has been worked with the battery only is +twenty-eight miles, the distance between Bologna +and Ferrara, and for greater distances it is necessary +to have recourse to induction coils.</p> + +<p>In this case, an induction coil is introduced +into the circuit at each station, and its primary +wire is traversed by a current from the local battery, +and so also is the sender, which is elsewhere +connected with the receiver by a commutator. +The secondary circuit of these coils is completed +through the earth and line wire. From +this arrangement it follows that the induced +current which influences the receiver in correspondence, +only produces its effect after a second +induction, produced on the primary wire of the<span class="pagenum" id="Page_129">129</span> +local coil, and it appears that this is a sufficient +effect; but the advantage of this arrangement is, +that it is possible to receive and transmit sounds +without the aid of anything but the commutator.</p> + +<p>Among other arrangements which have been +suggested, we may mention one in which, instead +of the bar magnet, a horseshoe magnet is used, +with a vibrating plate placed between its poles. +For this purpose the poles are tipped with iron, and +one of them is pierced with a hole which corresponds +to the mouthpiece of the instrument. The +two branches of the magnet are also furnished with +magnetising helices. When anything is spoken +before the hole, the vibrating plate causes induced +currents in the two helices: these currents would +be of opposite direction if the poles were of like +nature, but, since the magnetic poles are of contrary +nature, they are in the same direction. The +vibrating plate then acts like the two plates of +M. Trouvé’s instrument, which we have described +above.</p> + +<p>In another arrangement, lately made by Ader, +the receiver is only an ordinary two-branched +magnet, of which the armature is supported, at +about two millimètres from its poles, by a glass +plate to which it is glued, and the plate itself is +fastened to two rigid supports. In order to hear it +is only necessary to apply the ear to the plate. The +sender is a moveable rod of iron or carbon, which<span class="pagenum" id="Page_130">130</span> +rests on a fixed piece of carbon, with no pressure +except its own weight, and it supports a concave +disk, to which the speaker applies his mouth. +These two parts are so arranged as to move horizontally, +so that, when the instrument is suspended, +the circuit is forcibly disconnected by the fact of its +position, and is therefore closed until anyone takes +it up to speak. Speech is well reproduced by this +system, and may be transmitted to some distance if +it is made on a larger scale.</p> + +<p>Again, an anonymous inventor, in a little note +inserted in ‘Les Mondes,’ February 7, 1878, writes +as follows: ‘Since the intensity of the currents +produced in the telephone is in proportion to the +mass of soft iron which vibrates before the pole of +the magnet, and since, on the other hand, the plate +is sensitive in proportion to its tenuity, I employ, +instead of the ordinary plate, one reduced by nitric +acid to the least possible thickness, and I fix it to +a circle of soft iron, which keeps it stretched and +forms part of the same substance. This circle is +placed in a circular opening made inside the compartment. +The intensity of a telephone is much +increased when such a system replaces the ordinary +plate, even at one end of the line.’</p> + +<p>In order to obtain vibrating plates of extreme +tenuity, M. E. Duchemin thought of employing +very thin plates of mica, sprinkled with pulverised +iron fixed to the plate by a layer of silicate of +potash. The inventor asserts that it is possible to<span class="pagenum" id="Page_131">131</span> +correspond in a low voice with the aid of this system; +but it has this inconvenience, that the plate +will be broken by speaking too loud.</p> + +<p>Professor Jorgenson, of Copenhagen, has also +made a Bell telephone which produces very +intense sounds, and which has permitted him to +observe some curious effects. In this instrument, +the magnet is made in a mode analogous to Nicklès’ +tubular magnets. There is first a cylindrical +magnet with a core of soft iron at its upper end, +to which the coil is fitted; next, a magnetised tube, +formed of a steel ring, which encloses the first magnetic +system, and is connected with it by an iron +tube. Finally, above the polar extremities of this +system, there is the vibrating disk, with the same +arrangement as that of ordinary telephones, and +of which the superficies is large. If this plate is +only a millimètre in thickness, the words spoken +can be heard throughout a room; but the sounds +lose their clearness when the ear is approached to +the vibrating plate, the words are confused, and there +is the reverberation which is observed on speaking +in a place apt to produce echoes: the listener is, in +fact, stunned by the sounds produced. On using a +thicker plate—one, for example, of three or four +millimètres—the telephone only produces the effect +of the ordinary instruments, and it is necessary +to apply the ear to it.</p> + +<p>M. Marin Maillet, of Lyons, has suggested that +the sounds reproduced by the telephone might be<span class="pagenum" id="Page_132">132</span> +increased by reflecting them through a certain +number of reflectors, which, by concentrating them +in a focus on a resonator, would considerably +enlarge them. Since this idea was not accompanied +by experiments, it can hardly be regarded as +serious.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="TELEPHONIC_EXPERIMENTS"><span id="toclink_132"></span>TELEPHONIC EXPERIMENTS.</h2> +</div> + +<p>Since Mr. Bell’s experiments of which an account +has been given in the early part of this +work, much study has been given by men of +science and inventors to the effects produced in +this curious instrument, so as to ascertain its theory +and deduce improvements in its construction. We +will take a glance at these researches in succession.</p> + +<p><i>Experiments on the Effects produced by Voltaic +and Induced Currents.</i>—The comparative study of +the effects produced in the telephone by voltaic and +induced currents was one of the first and most +important. In 1873, as we have seen, Mr. Elisha +Gray converted the voltaic currents, which he +employed to cause the vibrations of his transmitting +plate, into induced currents by means of an +induction coil, such as Ruhmkorff’s. The voltaic +currents then traversed the primary helix of the +coil, and the induced currents reacted on the +receiving instrument, producing on its electro-magnetic +system the vibrations excited at the sending +station. When Mr. Edison designed his battery<span class="pagenum" id="Page_133">133</span> +telephone, he had recourse to the same means to +work his receiving telephone, since he had ascertained +that induced currents were superior to voltaic +currents. But this peculiarity of Mr. Edison’s +arrangement was not clearly understood from the +descriptions which reached Europe, so that several +persons believed that they had invented this arrangement—among +others, Colonel Navez and MM. +Pollard and Garnier.</p> + +<p>Colonel Navez, in an interesting paper on the +new telephonic system, presented to the Belgian +Royal Academy, February 2, 1878, only suggests +this arrangement as a mode of reproducing speech +at a great distance; but he quotes no experiment +which distinctly shows the advantages of this combination. +Twenty days later, MM. Pollard and +Garnier, unacquainted with Colonel Navez’s +researches, sent to me the results they had obtained +by similar means, and these results appeared +to me so interesting that I communicated them to +the Académie des Sciences, February 25, 1878. +In order that the importance of these results may +be clearly understood, I will repeat the text of M. +Pollard’s letter, addressed to me on February 20, +1878:</p> + +<p>‘With the object of increasing the variations of +electric intensity in the Edison system, we induce +a current in the circuit of a small Ruhmkorff coil, +and we fix the receiving telephone to the extremities +of the induced wire. The current received has the<span class="pagenum" id="Page_134">134</span> +same intensity as that of the inducing current, and +consequently the variations produced in the current +which works the telephone have a much wider +range. The intensity of the transmitted sounds is +strongly increased, and the value of this increase +depends upon the relative number of spirals in the +inducing and induced circuits. Our attempts to +determine the best proportions have been laborious, +since it is necessary to make a coil for each experiment; +we have hitherto obtained excellent results +with a small Ruhmkorff coil reduced to its simplest +form, that is, without condenser or contact-breaker. +The inducing wire is No. 16, and is wound in five +layers; the induced wire is No. 32, and in twenty +layers. The length of the coil is seven centimètres.</p> + +<p>‘The following is the most remarkable and +instructive experiment: When setting the sender +to work with a single Daniell cell, there is no +appreciable effect at the receiving station, at least +in the telephone which I have made, when it is +in immediate connection with the circuit; after +inserting the small induction coil, sounds become +distinctly audible, and their intensity equals that +of good ordinary telephones. Since the battery +current is only moderately intense, the points of +plumbago are not worn down, and the regulating +apparatus lasts for a long while. When a stronger +battery is used, consisting of six cells of bichromate +of potash (in tension) or twelve Leclanché<span class="pagenum" id="Page_135">135</span> +cells, sufficient intensity is obtained by the direct +action to make sounds nearly as audible as +in ordinary telephones; but when the induction +coil is inserted, the sounds become much more +intense, and may be heard at a distance of from +fifty to sixty centimètres from the mouthpiece. +Songs may, under such circumstances, be heard +at a distance of several yards; but the relative +increase does not appear to be so great as in the +case of the single Daniell cell.’</p> + +<p>On the other hand, ‘Les Mondes,’ March 7, +1878, contains an account of a series of experiments +made by Signor Luvini, Professor of Physics +at the Military Academy of Turin, which proved +that the introduction of electro-magnets into the +circuit which connects the two telephones sensibly +increases the intensity of sound. The maximum +effect is produced by placing one close to the transmitting, +and the other close to the receiving +telephone, and the introduction of other magnets +is of no use. The inducing wire of a Ruhmkorff +coil, when introduced into such a circuit, excited +no sensible effects of induction in the induced +circuit, and consequently could not set the telephone +in connection with this circuit at work. But +the current of a Clarke machine produces sounds +resembling the beats of a drum, which are deafening +when the ear is applied to the instrument: +they become very faint, however, at the distance of +a mètre. The currents of a Ruhmkorff machine are<span class="pagenum" id="Page_136">136</span> +still more energetic, and the sound fills a whole +room. By modifying the position of the lever of +the coil, the sound passes through different tones, +which are always in unison with the breaks of the +current, at least up to a certain pitch.</p> + +<p>This property of currents induced by the +Ruhmkorff coil has enabled M. Gaiffe to obtain by +their means a very simple mode of regulating +telephones, so as to produce in them the maximum +amount of sensibility. For this purpose he places +the telephone he proposes to regulate in the circuit +of an induction instrument with moveable helices +and graduated intensities. The sounds which +result from the vibrator are then reverberated from +the telephone, and are audible at a distance from +the instrument; by using a screw-driver, it is +possible to adjust the screw to which the free end +of the bar magnet of the instrument is fixed. It +can be tightened or loosened, so as to advance or +withdraw the other end of the magnet from the +vibrating plate of the telephone, and the process is +repeated until the maximum intensity of sound is +obtained.</p> + +<p>On the other hand, as the sounds given out by +the two telephones in correspondence are intense in +proportion to the degree of unison in the vibrations +produced by them, it is necessary to select those +which emit the same sounds for the same given +note; and the mode we have just described may be +employed with advantage, since it will be enough<span class="pagenum" id="Page_137">137</span> +to observe what instruments give the same note +in the condition of maximum sensibility, when +regulated in the same way by the induction machine.</p> + +<p>It is very important that the telephones in +correspondence should be well matched, not only to +ensure clear transmissions, but also with reference +to the tone of voice of those who are to use it. +The sound becomes more audible when the tone +of voice corresponds to the telephonic tone; and +for this reason some telephones repeat the voices +of women and children better than those of men, +and with others the reverse takes place.</p> + +<p>The telephonic vibrations vary in different +instruments, and these variations may be noted in +the way we have indicated.</p> + +<p>The advantages of induced currents in telephonic +transmissions may be easily understood, if +we consider that the variations of resistance in the +circuit, resulting from the greater or less range in +the vibrations of the transmitting plate, are of constant +value, and can only manifest their effects +distinctly in short circuits; consequently the articulate +sounds which result from them can only be +really appreciable in circuits of great resistance. +According to Mr. Warren de la Rue’s experiments +(reported in the ‘Telegraphic Journal,’ March 1, +1878), the currents produced by the vibrations +of the voice in an ordinary telephone represent +in intensity those of a Daniell cell traversing<span class="pagenum" id="Page_138">138</span> +100 megohms of resistance (or 10,000,000 kilomètres); +and it is plain that the simple question of +greater or less intensity in the currents acting on +the receiving telephone is not the only thing we +have to consider. With an energetic battery, it is +evident, in fact, that the differential currents will +always be more intense than the induced currents +produced by the action of the instrument. I +myself am inclined to believe that induced currents +owe the advantages they possess to the succession +of inverse currents and their brief duration. These +currents, of which M. Blaserna considers that the +duration does not exceed 1/200 of a second, are much +more susceptible than voltaic currents of the multiplied +vibrations which are characteristic of phonetic +vibrations, and especially since the succession +of inverse currents which take place discharge the +line, reverse the magnetic effects, and contribute to +make the action more distinct and rapid. We +cannot therefore be surprised that the induced +currents of the induction coil, which can be produced +under excellent conditions at the sending +station, since the circuit of the voltaic current +is then very short, are able to furnish results, not +only more effective than the voltaic currents from +which they take their origin, but even than the induced +currents resulting from the action of the Bell +telephone, since they are infinitely more energetic.</p> + +<p>As for the effects produced by the currents of +Bell telephones, which are relatively great when we<span class="pagenum" id="Page_139">139</span> +consider their size, they are easily explained from +the fact that they are produced under the influence +of the vibrations of the telephone plate, so that +their variations of intensity always maintain the +same proportion, whatever may be the resistance of +the circuit, and consequently they are not effaced +by the distance which divides the two telephones.</p> + +<p><i>Experiments on the part taken by the different +telephonic organs in the transmission of speech.</i>—In +order to introduce all the improvements of which a +telephone is capable, it is important to be quite +decided as to the effects produced in the several +parts of which it is composed, and as to the part +taken by the several organs which are at work. To +attain this object several men of science and +engineers have undertaken a series of experiments +which have produced very interesting results.</p> + +<p>One of the points on which it was most important +to throw light was that of ascertaining +whether the vibrating plate used in their telephone +receivers by Messrs. Bell and Gray is the only cause +of the complex vibrations which reproduce speech, +or if the different parts of the electro-magnetic +system of the instrument all conduce to this effect. +The experiments made by Mr. Page in 1837 on the +sounds produced by the resonant electro-magnetic +rods, and the researches pursued in 1846 by Messrs. +de la Rive, Wertheim, Matteucci, &c., on this curious +phenomenon, allow us to state the question, which +is certainly more complex than it at first appears.</p> + +<p><span class="pagenum" id="Page_140">140</span></p> + +<p>In order to start from a fixed point, it must +first be ascertained whether a telephone can transmit +speech without a vibrating plate. Experiments +made by Mr. Edison<a id="FNanchor_9" href="#Footnote_9" class="fnanchor">9</a> in November 1877, with +telephones provided with copper diaphragms, which +produced sounds, make the hypothesis credible; and +it received greater weight from the experiments +made by Mr. Preece and Mr. Blyth. The fact was +placed beyond a doubt by Mr. Spottiswoode (see +the ‘Telegraphic Journal’ of March 1, 1878), who +assures us that the vibrating plate of the telephone +may be entirely suppressed without preventing the +transmission of speech, provided that the polar extremity +of the magnet be placed quite close to the +ear; and it was after this that I presented to the +Académie des Sciences my paper on the theory +of the telephone, which led to an interesting discussion +of which I shall speak presently. At first +the authenticity of these results was denied, and +then an attempt was made to explain the sounds +heard by Mr. Spottiswoode as a mechanical transmission<span class="pagenum" id="Page_141">141</span> +of the vibrations, effected after the manner +of string telephones; but the numerous experiments +which have subsequently been made by Messrs. +Warwick, Rossetti, Hughes, Millar, Lloyd, Buchin, +Canestrelli, Wiesendanger, Varley, and many others, +show that this is not the case, and that a telephone +without a diaphragm can transmit speech electrically.</p> + +<p>Colonel Navez himself, who had first denied +the fact, now admits that a telephone without a +diaphragm can emit sounds, and even, under certain +exceptional conditions, can reproduce the human +voice; but he still believes that it is impossible to +distinguish articulate words.</p> + +<p>This uncertainty as to the results obtained by +the different physicists who have studied the +matter shows that at any rate the sounds thus +reproduced are not clearly defined, and that in +physical phenomena, only appreciable to our senses, +the appreciation of an effect so undefined must +depend on the perfection of our organs. We shall +presently see that this very slight effect can be +largely increased by the arrangement adopted by +Messrs. Bell and Gray, and we shall also see that, +by a certain mode of magnifying the vibrations, it +has been decisively proved that a telephone without +a diaphragm can readily reproduce speech. I +proceed to give the description of such a telephone, +which was shown by Mr. Millar at the meeting of +the British Association at Dublin in August 1878.</p> + +<p><span class="pagenum" id="Page_142">142</span></p> + +<p>This instrument consists of a small bar magnet, +three inches in length and 5/16 of an inch in width +and thickness, and a copper helix (No. 30) of +about six mètres in length is wound round the bar. +It is fixed in a box of rather thick pasteboard, +fitted above and below with two zinc plates, which +render it very portable. With a telephonic battery +sender and a single Leclanché cell, speech can +be perfectly transmitted; the whistling of an air, +a song, and even the act of respiration become +audible. It seems also that the instrument can +act without a magnet, merely with a piece of iron +surrounded by the helix; but the sounds are then +much fainter.</p> + +<p>Signor Ignace Canestrelli obtained the same +results by making one of the carbon telephonic +senders react on a telephone without a diaphragm, +by means of an induction coil influenced +by two Bunsen cells. He writes as follows on +the subject:</p> + +<p>‘With this arrangement I was able to hear the +sound of any musical instrument on a telephone +without a diaphragm: singing, speaking, and +whistling were perfectly audible. Whistling could +be heard, even when the telephone without a +diaphragm was placed at some distance from the +ear. In some cases, depending on the pitch of the +voice, on the distance of the sending station, and on +the joint pressure exerted by the carbons, I could +even distinguish words.</p> + +<p><span class="pagenum" id="Page_143">143</span></p> + +<p>‘I finally discharged the currents of the transmitter +into the coils of insulated copper wire with +which the two poles of a magnet were provided. +This magnet was placed on a musical box, made +of very thin slips of wood, and on placing the ear +at the opening of the box I obtained the same +results as with the ordinary telephones without a +diaphragm.’</p> + +<p>M. Buchin, after repeating experiments of the +same kind as the above, intimates that it is easy +to hear the sounds produced by a telephone without +a diaphragm, by introducing into the ear the +end of an iron rod, of which the other end is applied +to the active pole of the bar magnet of the +telephone. (See ‘Le Journal d’Electricité,’ October +5, 1878.)</p> + +<p>I repeat finally the account of some experiments +made by Mr. Hughes and M. Paul Roy +which are interesting from our present point of +view.</p> + +<p>1. If an armature of soft iron is applied to the +poles of an electro-magnet, with its two branches +firmly fixed on a board, and if pieces of paper are +inserted between this armature and the magnetic +poles, so as to obviate the effects of condensed +magnetism; if, finally, this electro-magnet is connected +with a speaking microphone, of the form +given in <a href="#il_39">fig. 39</a>, it is possible to hear the words +spoken in the microphone on the board which +supports the electro-magnet.</p> + +<p><span class="pagenum" id="Page_144">144</span></p> + +<p>2. If two electro-magnets are placed in communication +with a microphone, with their poles of +contrary signs opposite to each other, and if their +poles are separated by pieces of paper, speech will +be distinctly reproduced, without employing armature +or diaphragm. These experiments are, however, +delicate, and demand a practised ear.</p> + +<p>3. If, instead of causing the current produced +by a microphone to pass through the helix of a +receiving telephone, it is sent directly into the bar +magnet of this telephone in the direction of its axis—that +is, from one pole to another—the words pronounced +in the microphone may be distinctly heard. +This experiment by M. Paul Roy indicates, if it +is exact, that the electric pulsations which traverse +a magnet longitudinally will modify its magnetic +intensity. The experiment, however, demands +verification.</p> + +<p>Another point was obscure. It was important +to know whether the diaphragm of a telephone +really vibrates, or at least if its vibrations could +involve its displacement, such as occurs in an +electric vibrator, or in wind instruments which +vibrate with a current of air. M. Antoine Bréguet +has made some interesting experiments on the +subject, which show that such a movement cannot +take place, since speech was reproduced with great +distinctness from telephones with vibrating plates +of various degrees of thickness, and he carried the +experiment so far as to employ plates fifteen centimètres<span class="pagenum" id="Page_145">145</span> +in thickness.<a id="FNanchor_10" href="#Footnote_10" class="fnanchor">10</a> When pieces of wood, +caoutchouc, and other substances were laid upon +these thick plates, the results were the same. In +this case it cannot be supposed that the plates +were moved to and fro. I have moreover ascertained, +by placing a layer of water or of mercury on +these plates, and even on thin diaphragms, that no +sensible movement took place, at least when the +induced currents produced by the action of speaking +were used as the electric source. No ripples +could be seen on the surface of the liquid, even +when luminous reflectors were employed to detect +them. And indeed it can hardly be admitted that +a current not more intense than that of a Daniell +element, which has traversed 10,000,000 kilomètres +of telegraphic wire—a current which can only +show deviation on a Thomson galvanometer—should +be powerful enough to make an iron plate as +tightly stretched as that of a telephone vibrate by +attraction, even if we grant that the current was +produced by laying a finger on the diaphragm.</p> + +<p>Very nice photographic experiments do, however, +show that vibrations are produced on the +diaphragm of the receiving telephone; they are +indeed excessively slight, but Mr. Blake asserts +that they are enough to cause a very light index, +resting on the diaphragm, to make slight inflections<span class="pagenum" id="Page_146">146</span> +on a line which it describes on a register. +Yet this small vibration of the diaphragm does not +show that it is due to the effect of attraction, for it +may result from the act of magnetisation itself in +the centre of the diaphragm.<a id="FNanchor_11" href="#Footnote_11" class="fnanchor">11</a> An interesting experiment +by Mr. Hughes, repeated under different +conditions by Mr. Millar, confirms this opinion.</p> + +<p>If the magnet of a receiving telephone consists +of two magnetised bars, perfectly equal, separated +from each other by a magnetic insulator, +and they are so placed in the coil as to bring +alternately the poles of the same and of contrary +signs opposite to the diaphragm, it is known that +the telephone will reproduce speech better in the +latter case than in the former. Now, if the effects +were due to attraction, this would not be the case; +for the actions are in disagreement when the poles +of contrary signs are subjected to the same electric +influence, while they are in agreement when these +poles are of like signs.</p> + +<p>On the other hand, it is known that if several<span class="pagenum" id="Page_147">147</span> +iron plates are put together in order to form the +diaphragm of the receiver, the transmission of +sounds is much stronger than with a simple diaphragm; +and yet the attraction, if it has anything +to do with it, could only be exerted on one of the +diaphragms.</p> + +<p>It further appears that it is not merely the +magnetic core which emits sounds, but that they +are also produced with some distinctness by the +helices. Signor Rossetti had already ascertained +this fact, and had even remarked that they could be +animated by a slight oscillatory movement along +the bar magnet, when they were not fixed upon it. +Several observers, among others M. Paul Roy, Herr +Wiesendanger, and Signor Canestrelli, have since +mentioned similar facts, which are really interesting.</p> + +<p>‘If,’ writes M. Paul Roy, ‘a coil of fine wire, +which is at the extremity of the bar magnet of a +Bell telephone, receives the pulsatory currents +transmitted by a carbon telephone, it is only necessary +to bring the coil close to the ear in order to +hear the sounds.</p> + +<p>‘The sounds received in this way are very faint, +but become much stronger if a piece of iron is introduced +into the circuit coil. A magnet acts with +still greater force, even when it consists of a simple +magnetised needle. Finally, the sound assumes its +maximum intensity when an iron disk is inserted +between the ear and the coil.</p> + +<p>‘By placing the end of the coil to the ear, and<span class="pagenum" id="Page_148">148</span> +sending a current through it from the bar magnet, +it is ascertained that the sound is at its minimum +when the neutral line of the magnet is enclosed by +the coil, and that it increases until attaining its +maximum, when the magnet is moved until one of +its poles corresponds to the coil.</p> + +<p>‘This fact of the reproduction of sounds by a +helix is universal. Every induction coil and every +electro-magnet are capable of reproducing sound +when the currents of the sender are of sufficient +intensity.’</p> + +<p>Signor Canestrelli writes as follows: ‘With the +combination of a carbon telephone and one without +diaphragm or magnet—that is, with only a +simple coil—I was able to hear whistling through +the coil, placed close to the ear. This coil was of +very fine copper wire, and the currents were produced +through an induction coil by two Bunsen +elements. The contacts of the telephone were +in carbon, and it was inserted in the primary +circuit.</p> + +<p>‘I fastened the coil to the middle of a tightly +stretched membrane which served as the base of a +short metal cylinder. When a magnet was placed +near this part of the coil, the sounds were intensified, +and when I fixed the magnet in this position, +I could hear what was said.</p> + +<p>‘I afterwards substituted for the magnet a +second coil, fastened to a wooden bar, and on +causing the induced currents to pass into both coils<span class="pagenum" id="Page_149">149</span> +at once I was able to hear articulate speech, although +not without difficulty.</p> + +<p>‘Under these latter conditions I found it possible +to construct a telephone without a magnet, +but it required a strong current, and it was necessary +to speak into the sender in a special manner, +so as to produce strong and concentrated sounds.’</p> + +<p>Another very interesting experiment by M. A. +Bréguet shows that all the constituent parts of the +telephone—the handle, the copper rims, and the +case, as well as the diaphragm and the electro-magnet—can +transmit sounds. M. Bréguet ascertained +this fact by the use of string telephones, +which he attached to different parts of the telephone +on which the experiment was made. In +this way he was not only able to establish a correspondence +between the person who worked the +electric telephone and the one who was listening +through the string telephone, but he also made +several string telephones act, which were attached +to different parts of the electric telephone.</p> + +<p>These two series of experiments show that +sounds may be obtained from different parts of the +telephone without any very appreciable vibratory +movements. But Signor Luvini wished for a further +assurance of the fact, by ascertaining whether the +magnetisation of any magnetic substance, followed +by its demagnetisation, would involve a variation +in the form and dimensions of this substance. He +consequently caused a large tubular electro-magnet<span class="pagenum" id="Page_150">150</span> +to be made, which he filled with a quantity of +water, so that, when its two ends were corked, the +liquid should rise in a capillary tube fitted to one +of the corks. In this way the slightest variations +in the capacity of the hollow part of the electro-magnet +were revealed by the ascent or descent of +the liquid column. He next sent an electric +current of varying intensity through the electro-magnet, +but he was never able to detect any +change in the level of the water in the tube; +although by this arrangement he could measure a +change of volume of 1/30 of a cubic millimètre. It +appears from this experiment that the vibrations +produced in a magnetic substance under the influence +of successive magnetisations and demagnetisations, +are wholly molecular. Yet other experiments +made by M. Canestrelli seem to show that +these vibrations are so far sensible as to produce +sounds which can be detected by the microphone. +He writes as follows on the subject:</p> + +<p>‘When the broken currents of an induction +coil are discharged into a coil placed on a sounding-box, +it is possible to hear at a little distance the +sounds produced by the induced currents thus +generated. On approaching the magnet to the +opening of the coil, these sounds are intensified, +and the vibrations of the magnet become sensible +to the touch; this vibration might even be made +visible by suspending the magnet inserted into +the coil to a metallic wire, which is fitted to a membrane<span class="pagenum" id="Page_151">151</span> +stretched on a drum, and the latter will +then reproduce sounds. When the same magnet +is suspended to a microphone, it is possible, with +the aid of a telephone, to ascertain the same effects, +which are then increased.’</p> + +<p>We shall presently consider how these different +deductions are to be interpreted, so as to render +the true theory of the telephone intelligible; but, +before doing so, we will mention some other experiments +which are not without interest.</p> + +<p>We have seen that the experiments of Messrs. +Edison, Blyth, and Preece, show that sounds may +be reproduced by a telephone with a diaphragm +made of some unmagnetic substance, and they also +show, which is still more curious, that these sounds +may be transmitted under the influence of induced +currents produced by these diaphragms when they +are placed in vibration before the magnet. Messrs. +Edison and Blyth had already adduced this fact, +which was received with incredulity, but it has +been confirmed by Mr. Warwick in an article +published in the ‘English Mechanic.’ He writes +that in order to act upon the magnet, so as to produce +induced currents, something possessed of +greater energy than gas must first be made to +vibrate. It is not, however, necessary that this +substance should be magnetic, for diamagnetic +substances act perfectly.<a id="FNanchor_12" href="#Footnote_12" class="fnanchor">12</a> Mr. Preece sought for<span class="pagenum" id="Page_152">152</span> +the cause in the induced currents developed in +any conducting body when a magnet is moved<span class="pagenum" id="Page_153">153</span> +before it, currents which give rise to the phenomenon +discovered by Arago and known by the +name of magnetism by rotation. Yet these facts do +not appear to us to be sufficiently well established +to make the theory worthy of serious consideration, +and it is possible that the effects observed resulted +from simple mechanical transmissions.</p> + +<p>To conclude the account of these experiments, +we will add that Mr. W. F. Barrett thinks it somewhat +difficult to define the mode of vibration of the +diaphragm, since, while a certain amount of compression +exerted on the iron destroys the sounds<span class="pagenum" id="Page_154">154</span> +resulting from the peculiar effects of magnetisation, +a still stronger compression causes them to reappear. +It is certain that the question is full of +obscurity, and demands great research: it is enough +to have shown that the theory hitherto held is insufficient.</p> + +<p>On the other hand, Colonel Navez considers +that the intensity of sound reproduced in a telephone +depends not only on the range of vibrations, +but also on the vibrating surface and the effect it +produces on the stratum of air which transmits the +sound. (See paper by Colonel Navez in the +‘Bulletin de l’Académie de Belgique,’ July 7, +1878.)</p> + +<p><i>Experiments on the Effects which result from +Mechanical Shocks communicated to different parts +of a Telephone.</i>—If a piece of iron is applied to the +screw which holds the magnet of the ordinary telephone, +it is observed that the transmitted sounds are +more distinct, owing to the force supplied to the +active pole of the magnet; but at the moment when +the piece of iron is applied to the screw a distinct +noise is heard, which seems to be due to the mechanical +vibrations caused in the magnet at the moment +of the shock. M. des Portes, a lieutenant in the +French navy, has lately made some interesting +experiments on this class of phenomena. He has +observed that if, in a telephonic circuit of 90 +yards completed by the earth, the sending telephone +is reduced to a simple magnet, provided<span class="pagenum" id="Page_155">155</span> +with the coil which constitutes its electro-magnetic +organ, and if this magnet is suspended vertically +by a silken thread, with the coil above it, a blow +struck upon the magnet, either by a copper rod or +a piece of wood, will cause distinct sounds to be +produced in the receiving telephone—sounds which +will increase in intensity when the blow is struck +close to the coil, and which will become still +stronger, but less clear, if a vibrating plate of soft +iron is placed in contact with the upper pole of the +magnet.</p> + +<p>When the striking instrument is made of iron, +the sounds in question are more strongly marked +than if it is of wood, and when the magnet has a +vibrating disk applied to its active pole, a vibration +of the disk takes place at the moment when the +shock is heard.</p> + +<p>If the striking body is a magnet, the sounds +produced resemble those obtained when it is of +iron, if the effect is produced between poles of the +same nature; but if the poles are of contrary +natures, a second noise is heard after each blow, +which is produced by drawing away the magnet, +and which appears to be a blow struck with much +less force. The sound is of course increased if the +magnet is provided with its vibrating disk.</p> + +<p>If words are uttered on the vibrating disk of +the sending telephone, when it is applied to the +pole of the magnet, various sounds are heard on +the receiving telephone, somewhat similar to those<span class="pagenum" id="Page_156">156</span> +produced by vibrating one of the strings of a +violin, and the sound made in withdrawing the +disk from contact with the magnet is distinctly +heard in the receiver.</p> + +<p>The person who applies his ear to the vibrating +disk of the sender when it is arranged as above, +may hear the voice of anyone who speaks into +the receiver, but cannot distinguish the words, +owing, no doubt, to the condensed magnetism at +the point of contact between the magnet and the +vibrating disk, which slackens the magnetic variations +and makes it more difficult for them to take +place.</p> + +<p>A coil is not necessary in order to perceive the +blows struck upon the magnet with a rod of soft +iron. It is enough to wind three turns of naked +conducting wire, which acts as line wire, round one +end of the magnet, and the sounds perceived cease, +as in other experiments, when the circuit is broken, +plainly showing that they are not due to mechanical +transmission. It is a still more curious fact +that if the magnet is placed in the circuit, so as to +form an integral part of it, and if the two ends of +the conducting wire are wound round the ends of +the magnet, the blows struck upon the latter with +the soft iron rod are perceived in the telephone +as soon as one pole of the magnet is provided with +a vibrating disk.</p> + +<p>I have myself repeated M. des Portes’ experiments +by simply striking on the screw which, in<span class="pagenum" id="Page_157">157</span> +ordinary telephones, fastens the magnet to the instrument, +and I have ascertained that, whenever the +circuit was complete, the blows struck with an ivory +knife were repeated by the telephone: they were, it +is true, very faint when the vibrating disk was removed, +but very marked when the disk was in its +place. On the other hand, no sound was perceived +when the circuit was broken. These sounds +were louder when the blows were struck upon the +screw than when they were struck on the pole of +the magnet itself above the coil: for this reason, +that in the first case the magnet could vibrate +freely, while in the second the vibrations were +stifled by the fixed position of the bar magnet.</p> + +<p>These effects may be to some extent explained +by saying that the vibrations caused in the magnet +by the shock produce undulatory displacements of +the magnetised particles in the whole length of the +bar, and that induced currents would, according to +Lenz’s law, result in the helix from these displacements—currents +of which the force would increase +when the power of the magnet was further excited +by the reaction of the diaphragm, which acts as an +armature, and also by that of the striking instrument +when it also is magnetic. Yet it is more difficult to +explain M. des Portes’ later experiments, and the +effect may be produced by something more than +the ordinary induced currents.</p> + +<p>These are not the only experiments which +show the effects produced under the influence of<span class="pagenum" id="Page_158">158</span> +molecular disturbance of various kinds. Mr. +Thompson, of Bristol, has observed that if a piece +of iron and a tin rod placed perpendicularly on the +iron are introduced into the circuit of an ordinary +telephone, it is enough to strike the tin rod in +order to produce a loud sound in the telephone. +He has also shown that if the two ends of a bar +magnet are enclosed by two induction coils which +are placed in connection with the circuit of a telephone, +and if the flame of a spirit lamp is moved +below the magnet in the space dividing the two +coils, a distinct sound is heard as soon as the flame +exerts its influence on the bar magnet. This effect +is undoubtedly due to the weakening of the magnetic +force of the bar which is produced by the +action of heat. I have myself observed that a +scratching sound on one of the wires which connect +the telephones is heard in both of them, at +whatever point in the circuit the scratch is made. +The sounds produced are indeed very faint, but they +can be distinctly heard, and they become more +intense when the scratch is made on the binding-screws +of the telephone wires. These sounds +cannot result from the mechanical transmission of +vibrations, since they are imperceptible when the +circuit is broken. From these experiments it appears +that some sounds which have been observed +in telephones tried on telegraph stations may +arise from the friction of the wires on their supports—a +friction which produces those very intense<span class="pagenum" id="Page_159">159</span> +sounds which are sometimes heard on telegraphic +wires.</p> + +<p><i>Theory of the Telephone.</i>—It appears from the +several experiments of which we have spoken +that the explanation generally given of the effects +produced in the telephone is very imperfect, and +that the transmission of speech, instead of resulting +from the repetition by the membrane of the +receiving telephone (influenced by electro-magnetism) +of vibrations caused by the voice on the +membrane of the transmitting membrane, is due +to molecular vibrations produced in the whole +electro-magnetic system, and especially on the +magnetic core contained in the helix. These vibrations +must be of the same nature as those +which have been observed in resonant electro-magnetic +rods by MM. Page, de la Rive, Wertheim, +Matteucci, &c., and these have been employed +in telephones by Reiss, by Cecil and Leonard +Wray, and by Vanderweyde.</p> + +<p>According to this hypothesis, the principal +office of the vibrating plate consists in its reaction, +in order to produce the induced currents when the +voice has placed it in vibration, and by this reaction +on the polar extremity of the bar magnet it +strengthens the magnetic effects caused in the +centre of the bar when it vibrates under the electro-magnetic +influence, or at least when it is affected +by the magnet. Since the range of these vibrations +for a single note is great in proportion to the<span class="pagenum" id="Page_160">160</span> +flexibility of the note, and since, on the other hand, +the variations in the magnetic condition of the +plate are rapid in proportion to the smallness of +its mass, the advantage of employing, as Mr. +Edison has done, very thin and relatively small +plates is readily understood. In the case of transmission, +the wider range of vibration increases the +intensity of the induced currents transmitted. In +the case of reception the variations in the magnetising +force which produces the sounds are rendered +clearer and more distinct, both in the armature +membrane and in the bar magnet: something +is gained, therefore, in each case. This hypothesis +by no means excludes the phonetic effects of the +mechanical and physical vibrations which may be +produced in the armature plate under the influence +of magnetisation and demagnetisation to which it +is subjected, and these join their influence to that +of the magnetic core.</p> + +<p>What is the nature of the vibrations sent into +the receiving telephone? This question is still +obscure, and those who have studied it are far +from being in agreement: as early as 1846 it was +the subject of an interesting discussion between +MM. Wertheim and de la Rive, and the new discoveries +render it still more complex. M. Wertheim +considers that these vibrations are at once +longitudinal and transverse, and arise from attractions +exchanged between the spirals of the +magnetising helix and the magnetic particles of<span class="pagenum" id="Page_161">161</span> +the core. M. de la Rive holds that in the case we +are considering the vibrations are simply longitudinal, +and result from molecular contractions and +expansions produced by the different combinations +assumed by the magnetic molecules under the +influence of magnetisation and demagnetisation. +This appears to us to be the most natural explanation, +and it seems to be confirmed by the +experiment made by M. Guillemin in 1846. M. +Guillemin ascertained that if a flexible iron rod, +surrounded by a magnetising helix, is kept in position +by a vice at one end, and bent back by a weight +at the other, it can be made to return instantly to +its normal position by sending a current through +the magnetising helix. This recovery can in such +a case be due to nothing but the contraction +caused by the magnetic molecules, which, under the +influence of their magnetisation, tend to produce +intermolecular attractions, and to modify the elastic +conditions of the metal. It is known that when +iron is thus magnetised it becomes as hard as steel, +and a file makes no impression on its surface.</p> + +<p>It is at any rate impossible to dispute that +sounds are produced in the magnetic core, as well +as in the armature, under the influence of intermittent +electric action. These sounds may be +musical or articulate; for as soon as the sender has +produced the electric action required, there is no +reason why vibrations which are effected in a +transverse or longitudinal direction should transmit<span class="pagenum" id="Page_162">162</span> +the one more than the other. These vibrations +may, as we have seen, be termed microscopic.</p> + +<p>Signor Luvini, who shares our opinion of the +foregoing theory, does not, however, think it wholly +satisfactory, unless account is taken of the reaction +caused by the bar magnet on the helix which surrounds +it. ‘There cannot,’ he says, ‘be <em>action</em> without +<em>reaction</em>, and consequently the molecular action +produced in the magnet ought to cause corresponding +variations in the helix, and these two effects ought to +contribute to the production of sounds.’ He supports +this remark by a reference to Professor Rossetti’s experiment, +of which we have spoken above.</p> + +<p>We believe, however, that this double reaction +of which Signor Luvini speaks is not indispensable, +for we have seen that insulated helices can produce +sounds; it is true that the spirals, reacting on each +other, may be the cause of this.</p> + +<p>The difficulty of explaining the production of +sounds in an electro-magnetic organ destitute of +armature caused the authenticity of the experiments +we have described to be at first denied, and +Colonel Navez started a controversy with us which +is not likely to be soon terminated; yet one result +of this controversy is that Colonel Navez was obliged +to admit <em>that the sound of the human voice may be +reproduced by a telephonic receiver without a disk</em>. +But he still believes that this reproduction is so faint +that it is not possible to recognise articulate words, +and he maintains that the transverse vibrations of<span class="pagenum" id="Page_163">163</span> +the disk, which are due to effects of attraction, are +the only ones to reproduce articulate speech with +such intensity as to be of any use.</p> + +<p>It is certain that the articulation of speech +requires a somewhat intense vibration which cannot +easily be produced in a telephone without a +diaphragm; for it must be remembered that in an +instrument so arranged, the magnetic effects are +reduced in a considerable ratio, which is that of the +magnetic force developed in the magnet, multiplied +by itself, and that so faint an action as that effected +in a telephone becomes almost null when, in consequence +of the suppression of the armature, it is +only represented by the square root of the force +which produced it. It is therefore possible that +the sounds which are hardly perceptible in a telephone +without a diaphragm become audible when +the cause which provokes them is multiplied by +itself, and when there are in addition the vibrations +produced in the heart of the armature itself, influenced +by the magnetisations and demagnetisations +to which it is subjected.</p> + +<p>In order to show that the action of the +diaphragm is less indispensable than Colonel +Navez seems to imagine, and that its vibrations +are not due to electro-magnetic attractions, it will +be enough to refer to Mr. Hughes’s experiments, +which we have mentioned above. It is certain +that if this were the effect produced, we should +hear better when the two bar magnets present<span class="pagenum" id="Page_164">164</span> +their poles of the same nature before the diaphragm, +than when they present the poles of +contrary natures, since the whole action would then +converge in the same direction. Again, the more +marked effects obtained with multiple diaphragms +in juxtaposition completely exclude this hypothesis. +It is, however, possible that in electro-magnetic +telephones the iron diaphragm, in virtue of the rapid +variations of its magnetic condition, may contribute +to render the sounds clearer and more distinct; it +may react in the way the tongue does; but we +believe that the greater or less distinctness of the +articulate sounds must be chiefly due to the range +of vibrations. Thus Mr. Hughes has shown that +the carbons of metallised wood employed in his +microphonic speakers were to be preferred to +retort carbons for the transmission of speech, for +the very reason that they had less conductivity, +so that the differences of resistance which result +from differences of pressure are more marked, +and consequently it is easier to seize the different +degrees of vocal sounds which constitute articulate +speech.</p> + +<p>It must be clearly understood that what we +have just said only applies to the Bell telephone, +that is, to a telephone in which the electric currents +have such a faint intensity that it cannot be supposed +there is any external attractive effect. When +these currents are so energetic as to produce such +an effect, a transverse electro-magnetic vibration<span class="pagenum" id="Page_165">165</span> +certainly takes place, which is added to the molecular +vibration, and helps to increase the sounds +produced. But it is no less true that this transverse +vibration by attraction or by movement of +the diaphragm is not necessary for the reproduction +of sounds, whether musical or articulate.</p> + +<p>We are not now concerned with the discussion +of magnetic effects; there has been an advance in +science since Colonel Navez started the controversy, +and we must ask how his theory of the movements +of the telephone diaphragm by attraction +will explain the reproduction of speech by a +receiving microphone destitute of any electro-magnetic +organ, and I can assert that my experiments +show that there can be no mechanical +transmission of vibrations, since no sound is +heard when the circuit is broken or deprived of +its battery. Colonel Navez must therefore accept +the molecular vibrations. This certainly gives us +a new field for study; but it is because European +men of science persist in remaining bound by +incomplete theories that we have allowed the +Americans who despise them to reap the glory of +the great discoveries by which we have lately been +astonished.</p> + +<p>The experiments quoted above show that +sounds may be reproduced not only by simple +helices without an electro-magnetic organ, but +also by the plates of a condenser, in spite of the +pressure exerted upon them; and when we add<span class="pagenum" id="Page_166">166</span> +to this the effects I have just pointed out, it may +be supposed that vibrations of sound must result +from every reaction between two bodies which has +the effect of producing abruptly and at close intervals +modifications in the condition of their +electric or magnetic equilibrium. It is known that +the presence of ponderable matter is necessary for +the production of electric effects, and it is possible +that the molecular vibrations of which I have +spoken may be the result of molecular movements, +due to the variations of the electric force which +holds the molecules in a special condition of reciprocal +equilibrium.</p> + +<p>In conclusion, the theory of the telephone and +microphone, considered as reproductive organs of +speech, is still far from being perfectly clear, and +it would be imprudent to be too positive on questions +of such recent origin.</p> + +<p>The theory of the electric transmission of +sounds in electro-magnetic telephones is somewhat +complex. It has been seen that they can be +obtained from diaphragms of non-magnetic substance, +and even from simple mechanical vibrations +produced by shocks. Are we to ascribe them in +the first case to the inductive reaction of the +magnet on the vibrating plate, and in the second +case to the movements of magnetic particles before +the spirals of the helix? The matter is still very +obscure; yet it is conceivable that the modifications +of the inducing action of the magnet on the<span class="pagenum" id="Page_167">167</span> +vibrating diaphragm may involve variations in the +magnetic intensity, just as we can admit an effect +of the same kind due to the approach and withdrawal +of the magnetic particles of the spirals of +the helix; M. Trève, however, believes that there +is in the latter case a special action, which he has +already had occasion to study under other circumstances, +and he sees in the current thus caused the +effect of the transformation of the mechanical +labour produced amidst the magnetic molecules. +The question is complicated by the fact that these +effects are often produced by purely mechanical +transmissions.</p> + +<p>There is another point to consider, on which +Colonel Navez has made some interesting remarks; +that is, whether the effects in the receiver +are stronger with permanent than with temporary +magnets. In the first model of the telephone, +exhibited by Mr. Bell at Philadelphia, the receiver +was, as I have said, made of a tubular electro-magnet, +furnished with a vibrating disk at its +cylindrical pole; but this arrangement was abandoned +by Mr. Bell, with the object, as he states +in his paper, of rendering his instrument both +a receiver and a sender.<a id="FNanchor_13" href="#Footnote_13" class="fnanchor">13</a> Yet Colonel Navez +maintains that the magnet plays an important<span class="pagenum" id="Page_168">168</span> +part, and is even indispensable under the present +conditions of its form. ‘It is possible,’ he says, +‘under certain circumstances, and by making the +instrument in a special way, to make a Bell receiver +speak without a permanent magnet, yet with an +instrument of the usual construction the sound +ceases when the magnet is withdrawn and replaced +by a cylinder of soft iron. In order to restore the +voice of the telephone, it is enough to approach +the pole of a permanent magnet to the cylinder +of soft iron. It follows from these experiments +that a Bell telephone cannot act properly unless +the disk is subjected to an initial magnetic tension +obtained by means of a permanent magnet. It +is easy to deduce this assertion from a consideration +of the theory.’</p> + +<p>The assertion may be true in the case of Bell +telephones, which are worked by extremely weak +currents, but when these currents are relatively +strong, all electro-magnets will reproduce speech +perfectly, and we have seen that M. Ader made +a telephone with the ordinary electro-magnet +which acted perfectly.</p> + +<p>The action of the currents sent through the +helix of a telephone can be easily explained. +Whatever may be the magnetic conditions of the +bar, the induced currents of different intensity +which act upon it produce modifications in its +magnetic state, and hence the molecular vibrations +follow from contraction and expansion. These<span class="pagenum" id="Page_169">169</span> +vibrations are likewise produced in the armature +under the influence of the magnetisations and demagnetisations +which are produced by the magnetic +action of the core, and they contribute to the +vibrations of the core itself, while at the same +time the modifications in the magnetic condition +of the system are increased by the reaction of the +two magnetic parts upon each other.</p> + +<p>When the bar is made of soft iron, the induced +currents act by creating magnetisations of greater +or less energy, followed by demagnetisations which +are the more prompt since inverse currents always +succeed to those which have been active, and this +causes the alternations of magnetisation and demagnetisation +to be more distinct and rapid. +When the bar is magnetised, the action is differential, +and may be exerted in either direction, according +as the induced currents corresponding to +the vibrations which are effected pass through the +receiving coil in the same or opposite direction as +the magnetic current of the bar. If these currents +are in the same direction, the action is strengthening, +and the modifications are effected as if a +magnetisation had taken place. If these currents +are of opposite direction, the inverse effect is +produced; but, whatever the effects may be, +the molecular vibrations maintain the same +reciprocal relations and the same height in +the scale of musical sounds. If the question +is considered from the mathematical point of<span class="pagenum" id="Page_170">170</span> +view, we find the presence of a constant, corresponding +with the intensity of the current, which +does not exist in mechanical vibrations, and which +may possibly be the cause of the peculiar tone of +speech reproduced by the telephone, a tone which +has been compared to the voice of Punch. M. +Dubois Raymond has published an interesting +paper on this theory, which appeared in ‘Les +Mondes,’ February 21, 1878, but we do not reproduce +it here, since his remarks are too scientific +for the readers for whom this work is intended. +We will only add that Mr. C. W. Cunningham +asserts that the vibrations produced in a telephone +cannot be manifested under precisely the same conditions +as those which affect the tympanum of the +ear, because the latter has a peculiar funnel-shaped +form, which excludes every fundamental note, specially +adapted to it, and this is not the case with +the bars and magnetic plates which possess fundamental +notes capable of greatly altering the half-tones +of the voice. He considers the alteration of +the voice observed in the telephone must be ascribed +to these fundamental notes.</p> + +<p><i>M. Wiesendanger’s Thermophone.</i>—M. Wiesendanger, +in an article inserted in the ‘English +Mechanic and World of Science,’ September 13, +1878, ascribes the reproduction of speech in certain +telephones to vibratory movements resulting from +molecular expansions and contractions produced +by variations of temperature, and these variations<span class="pagenum" id="Page_171">171</span> +would follow from the currents of varying intensity +which are transmitted through the telephonic +circuits. He was conscious of one objection to +this theory, namely, that the movements of expansion +and contraction due to heat are slowly +produced, and consequently are not capable of +substantial action, rapid enough to produce vibrations; +but he considers that molecular effects need +not take place under the same conditions as those +which are displayed in the case of material substances.</p> + +<p>M. Wiesendanger believes that this hypothesis +will explain the reproduction of speech in the +receiving microphones of Mr. Hughes, and that it +may even be applied to the theory of the electro-magnetic +telephone, if we consider that a magnetising +helix, as well as a magnetic core, round +which an electric current circulates, is more or +less heated, according to the intensity of the +current which traverses it, especially when the wire +of the helix and the core are bad conductors of +electricity and of magnetism. Pursuing this idea, +M. Wiesendanger has sought to construct telephones +in which calorific effects are more fully +developed, and with this object he used very fine +wire of German silver and platinum to make the +coils. He ascertained that these coils could produce +sounds themselves, and, to increase their intensity, +he put them between disks of iron, or on +tin tubes, placed on resonant surfaces close to the<span class="pagenum" id="Page_172">172</span> +disks. In this way he says that he was able to +make a good receiving telephone without employing +magnets. He afterwards arranged the instrument +in different ways, of which the two following +are the most noteworthy.</p> + +<p>In the first, the electro-magnetic system was +simply formed by a magnetic disk with a helix +wound round it, of which the wire was in connection +with the circuit of a microphone, and which +was fastened to the centre of the parchment membrane +of an ordinary string telephone; the disk +consisted of two iron plates separated by a carbon +disk of smaller diameter, and the whole was so +compressed as to form a solid mass.</p> + +<p>In the second, the helix was wound on a tin +tube, six inches long and five-eighths of an inch in +diameter, which was soldered by merely a point to +the centre of the diaphragm of an ordinary telephone.</p> + +<p>The inventor asserts that the tube and diaphragm +only act as resonators, and that the sounds +produced by this instrument are nearly the same +as those obtained from the ordinary string telephone: +the tunes of a musical box were heard, +and the reproduction of speech was perfect, both +in intensity and in distinctness of sound; it even +appeared that telephonic sounds were audible with +the tin tube alone, surrounded by the helix. M. +Wiesendanger says that ‘these different receiving +telephones show clearly that the diaphragm and<span class="pagenum" id="Page_173">173</span> +magnet are not essential, but merely accessory, +parts of a telephone.’</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="VARIOUS_EXPERIMENTS_MADE_WITH_THE"><span id="toclink_173"></span>VARIOUS EXPERIMENTS MADE WITH THE +TELEPHONE.</h2> +</div> + +<p>We must now consider a series of experiments +which demonstrate the wonderful properties of the +telephone, and which may also give some indication +of the importance of the influences by which it is +liable to be affected.</p> + +<p><i>Experiments by M. d’Arsonval.</i>—We have seen +that the telephone is an extremely sensitive instrument, +but its sensitiveness could scarcely be appreciated +by ordinary means. In order to gauge it, M. +d’Arsonval has compared it to the nerve of a frog, +which has hitherto been regarded as the most +perfect of all galvanoscopes, and it appears from +his experiments that the sensitiveness of the +telephone is two hundred times greater than that of +the frog’s nerve. M. d’Arsonval has given the +following account of his researches in the records of +the Académie des Sciences, April 1, 1878:</p> + +<p>‘I prepared a frog in Galvani’s manner. I +took Siemens’ instrument of induction, used in +physiology under the name of the chariot instrument. +I excited with the ordinary pincers the +sciatic nerve, and I withdrew the induced coil until +the nerve no longer responded to the electric excitement. +I then substituted the telephone for +the nerve, and the induced current, which had<span class="pagenum" id="Page_174">174</span> +ceased to excite the latter, made the instrument +vibrate strongly. I withdrew the induced coil, and +the telephone continued to vibrate.</p> + +<p>‘In the stillness of night I could hear the +vibration of the telephone when the induced coil +was at a distance fifteen times greater than the +minimum at which the excitement of the nerve +took place; consequently, if the same law of inverse +squares applies to induction and to distance, +it is evident that the sensitiveness of the telephone +is two hundred times greater than that of the nerve.</p> + +<p>‘The sensitiveness of the telephone is indeed +exquisite. We see how much it exceeds that +of the galvanoscopic frog’s leg, and I have thought +of employing it as a galvanoscope. It is very +difficult to study the muscular and nervous currents +with a galvanometer of 30,000 turns, because +the instrument is deficient in instantaneous action, +and the needle, on account of its inertia, cannot +display the rapid succession of electric variations, +such as are effected, for example, in a muscle thrown +into electric convulsion. The telephone is free from +this inconvenience, and it responds by vibration to +each electric change, however rapid it may be. The +instrument is therefore well adapted for the study +of electric tetanus in the muscle. It is certain that +the muscular current will excite the telephone, since +this current excites the nerve, which is less sensitive +than the telephone. But for this purpose some +special arrangement of the instrument is required.</p> + +<p><span class="pagenum" id="Page_175">175</span></p> + +<p>‘It is true that the telephone can only reveal +the variations of an electric current, however faint +they may be; but I have been able, by the use +of a very simple expedient, to reveal by its means +the presence of a continuous current, also of extreme +faintness. I send the current in question +into the telephone, and, to obtain its variations, I +break this current mechanically with a tuning-fork. +If no current is traversing the telephone, it remains +silent. If, on the other hand, the faintest current +exists, the telephone vibrates in unison with the +tuning-fork.’</p> + +<p>Professor Eick, of Wurzburg, has also used the +telephone for physiological researches, but in a +direction precisely opposite to that explored by +M. d’Arsonval. He ascertained that when the +nerves of a frog were placed in connection with a +telephone, they were forcibly contracted when anyone +was speaking into the instrument, and the force +of the contractions chiefly depended on the words +pronounced. For instance, the vowels <i>a</i>, <i>e</i>, <i>i</i> produced +hardly any effect, while <i>o</i> and especially <i>u</i> +caused a very strong contraction. The words <em>Liege +still</em>, pronounced in a loud voice, only produced a faint +movement, while the word <em>Tucker</em>, even when +spoken in a low voice, strongly agitated the frog. +These experiments, reminding us of those by +Galvani, were necessarily based on the effects produced +by the induced currents developed in the +telephone, and they show that if this instrument is<span class="pagenum" id="Page_176">176</span> +a more sensitive galvanoscope than the nerve of a +frog, the latter is more susceptible than the most +perfect galvanometer.</p> + +<p><i>Experiments by M. Demoget.</i>—In order that he +might compare the intensity of the sounds transmitted +by the telephone with the intensity of +original sounds, M. Demoget placed two telephones +in an open space. He held the first to +his ear, while his assistant withdrew to a distance, +constantly repeating the same syllable with the +same intensity of tone in the second instrument. +He first heard the sound transmitted by the telephone, +and then the sound which reached him +directly, so that comparison was easy, and he +obtained the following results.</p> + +<p>At a distance of 93 yards the original and the +transmitted sounds were received with equal intensity, +while the vibrating disk was about 5 centimètres +from the ear. At this moment, therefore, +the relative intensity was as 25 to 81,000,000. In +other words, the sound transmitted by the telephone +was only 1/3000000 of the emitted sound. ‘But,’ +said M. Demoget, ‘since the stations at which we +worked could not be regarded as two points freely +vibrating in space, the ratio may be reduced by +one half on account of the influence of the earth, +and the sound transmitted by the telephone may +be supposed to be 1,500,000 times weaker than +that emitted by the voice.</p> + +<p>‘Again, since we know that the intensity of the<span class="pagenum" id="Page_177">177</span> +two sounds is in proportion to the square of the +range of vibrations, it may be concluded that the +vibrations of the two telephone disks were in direct +proportion to the distance, that is, as 5 to 9,000, +or that the vibrations of the sending telephone +were eighteen hundred times greater than those +of the receiving telephone. These latter may +therefore be compared to molecular vibrations, since +the range of those of the sending telephone was +extremely small.</p> + +<p>‘Without in any degree detracting from the +merit of Bell’s remarkable invention,’ continues M. +Demoget, ‘it follows from what I have said above +that the telephone, considered as a sending instrument, +leaves much to be desired, since it only +transmits the 18/100 part of the original power; and +if it has produced such unexpected results, this +is due to the perfection of the organ of hearing, +rather than to the perfection of the instrument itself.’</p> + +<p>M. Demoget considers this loss of power which +takes place in the telephone to be chiefly owing +to the eight transformations in succession to which +sound is subjected before reaching the ear, setting +aside the loss due to the electric resistance of the +line, which might in itself suffice to absorb the +whole force.</p> + +<p>In order to estimate the force of the induced +currents which act upon a telephone, M. Demoget +has attempted to compare them with currents of +which the intensity is known, and which produce<span class="pagenum" id="Page_178">178</span> +vibrations of like nature and force: for this purpose +he has made use of two telephones, <span class="allsmcap">A</span> and <span class="allsmcap">B</span>, communicating +through a line 22 yards in length. +He placed a small file in slight contact with the +vibrating disk of the telephone <span class="allsmcap">A</span>, and caused friction +between the file and a metallic plate: the sound +thus produced was necessarily transmitted by the +telephone <span class="allsmcap">B</span>, with an intensity which could be +estimated. He then substituted a battery for the +telephone <span class="allsmcap">A</span>, and the file was introduced into +the circuit by connecting it with one of the poles. +The current could only be closed by the friction of +the file with the plate, which had a spring, and was +in communication with the other end of the circuit. +In this way broken currents were obtained, which +caused vibration in the telephone <span class="allsmcap">B</span>, and produced +a sound of which the intensity varied with the +strength of the battery current. In this way M. +Demoget endeavoured to find the electric intensity +capable of producing a sound similar to that of the +telephone <span class="allsmcap">A</span>, and he ascertained that it corresponded +in intensity to that produced in a small thermo-electric +battery formed of an iron and a copper +wire, two millimètres in diameter, flattened at the +end, and soldered to the tin: the faint current produced +by this battery only caused a short wire +galvanometer to deviate two degrees.</p> + +<p>This estimate does not appear to us to unite so +many conditions of accuracy as to enable us to +deduce from it the degree of sensitiveness possessed<span class="pagenum" id="Page_179">179</span> +by a telephone, a sensitiveness which the experiments +of Messrs. Warren de la Rue, Brough, and +Peirce show to be much greater. Mr. Warren de la +Rue, as we have seen, used Thomson’s galvanometer, +and compared the deviation produced on +the scale of this galvanometer with that caused by +a Daniell cell traversing a circle completed by +a rheostat: he ascertained that the currents discharged +by an ordinary Bell telephone are equivalent +to those of a Daniell cell traversing 100 +megohms of resistance, that is, 6,200,000 miles +of telegraphic wire. Mr. Brough, the Director +of Indian Telegraphs, considers that the strongest +current which at any given moment causes a Bell +telephone to work does not exceed 1/1000000 of the +unit of current, that is, one Weber, and the current +transmitted to the stations on the Indian telegraphic +line is 400,000 times as strong. Finally, +Professor Peirce, of Boston, compares the effects +of the telephonic current with those which would +be produced by an electric source of which the +electro-motive force should be 1/200000 part of a volt, +or one Daniell cell. Mr. Peirce justly remarks +that it is difficult to estimate the real value of +these kinds of currents at any precise sum, since it +essentially varies according to the intensity of the +sounds produced on the transmitting telephone; but +it may be affirmed that it is less than the 1/1000000 part +of the current usually employed to work the instruments +on telegraphic lines.</p> + +<p><span class="pagenum" id="Page_180">180</span></p> + +<p>Signor Galileo Ferraris, who has recently published +an interesting treatise on this question in the +‘Atti della Reale Accademia delle Scienze di +Torino’ (June 13, 1878), states that the intensity of +the currents produced by the ordinary Bell telephone +varies with the pitch of the sound emitted.</p> + +<p><i>Experiments by M. Hellesen, of Copenhagen.</i>—In +order to estimate the reciprocal effects of different +parts of a telephone, M. Hellesen has made telephones +of the same size with three different arrangements +which act inversely to each other. The first +was of the ordinary form, the second like that of Bell’s +first system, that is, with a membrane supporting a +small iron armature on its centre, instead of a vibrating +disk, and the third telephone consisted of a +hollow cylindrical magnet, with the vibrating disk +fixed to one of its poles, and the disk was adapted +to move before a flat, snail-shaped spiral, of which +the number of spirals equalled those of the two other +helices. In this last arrangement, the induced +currents resulting from the vibrations of the voice +might be assimilated to those which follow from +the approximation and withdrawal of the two +parallel spirals, one of which should be traversed by +a current. It is this last arrangement which Mr. +Bell has adopted as producing the best effects, and +it is rare in the history of discoveries that an +inventor hits at once on the best arrangement of his +instrument.</p> + +<p><i>Experiments by M. Zetsche.</i>—There are always a<span class="pagenum" id="Page_181">181</span> +few perverse minds, impelled by a spirit of contradiction +to deny evidence, and thus they attempt to +depreciate a discovery of which the glory irritates +them. The telephone and the phonograph have +been the objects of such unworthy criticism. It has +been said that electric action had nothing to do +with the effects produced in the telephone, and that +it only acted under the influence of mechanical +vibrations transmitted by the conducting wire, just +as in a string telephone. It was in vain to demonstrate +to these obstinate minds that no sound +is produced when the circuit is broken, and in order +to convince them M. Zetsche has made some experiments +to show, from the mode in which sound +is propagated, that it is absurd to ascribe the sound +produced in a telephone to mechanical vibration. +He wrote to this effect in an article inserted in the +‘Journal Télégraphique,’ Berne, January 25, 1878:</p> + +<p>‘The correspondence by telephone between +Leipzig and Dresden affords another proof that +the sounds which reproduce words at the receiving +station are due to electric currents, and not to +mechanical vibrations. The velocity with which +sound is transmitted by vibrations on the wire, in +the case of longitudinal undulations, may be estimated +at three miles one furlong a second, so that +the sound ought to traverse the distance from +Leipzig to Dresden in 25 seconds. The same time +ought to elapse before receiving the answer. Consequently +there should be an interval of more than<span class="pagenum" id="Page_182">182</span> +three-quarters of a minute allowed for each exchange +of communication, which is by no means the case.’</p> + +<p><i>Experiments which may be made by anyone.</i>—We +will conclude this chapter, devoted to the +account of the different experiments made with +the telephone, by the mention of a singular experiment, +which, although easily performed, has only +been suggested a few months ago by a Pennsylvanian +newspaper. It consists in the transmission +of speech by a telephone simply laid on some part +of the human body adjacent to the chest. It has +been asserted that any part of the body will produce +this effect, but according to my experience, +I could only succeed when the telephone was firmly +applied to my chest. Under such conditions, and +even through my clothes, I could make myself +heard when speaking in a very loud voice, from +which it appears that the whole of the human body +takes part in the vibrations produced by the voice. +In this case, the vibrations are mechanically +transmitted to the diaphragm of the sending telephone, +not by the air, but by the body itself acting +on the outside of the telephone.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="THE_MICROPHONE"><span id="toclink_182"></span>THE MICROPHONE.</h2> +</div> + +<p>The microphone is in fact only the sender +of a battery telephone, but with such distinctive +characteristics that it may be regarded as an +original invention which is entitled to a special<span class="pagenum" id="Page_183">183</span> +name. The invention has lately given rise to an +unfortunate controversy between its inventor, Mr. +Hughes, and Mr. Edison, the inventor of the carbon +telephone and the phonograph—a controversy +which has been embittered by the newspapers, and +for which there were no grounds. For although +the scientific principle of the microphone may +appear to be the same as that of Mr. Edison’s +carbon sender, its arrangement is totally different, +its mode of action is not the same, and the effect +required of it is of quite another kind. Less than +this is needed to constitute a new invention. +Besides, a thorough examination of the very +principle of the instrument must make us wonder +at Mr. Edison’s claim to priority. He cannot +in fact regard as his exclusive possession the discovery +of the property possessed by some substances +of moderate conductivity of having this +power modified by pressure. In 1856, and often +subsequently, as for example in 1864, 1872, 1874, +and 1875, I made numerous experiments on this +point, which are described in the first volume of +the second edition of my ‘Exposé des applications +de l’Electricité,’ and also in several papers presented +to the Académie des Sciences, and inserted in their +<i lang="fr">Comptes rendus</i>. M. Clarac again, in 1865, employed +a tube made of plumbago, and provided +with a moveable electrode, to produce variable +resistances in a telegraphic circuit. Besides, in +Mr. Edison’s telephonic sender, the carbon disk, as<span class="pagenum" id="Page_184">184</span> +we have seen, must be subjected to a certain +initial pressure, in order that the current may +not be broken by the vibrations of the plate on +which it rests, and consequently the modifications +of resistance in the circuit which produce articulate +sounds are only caused by greater or less increase +and diminution of pressure, that is, by differential +actions. We shall presently see that this is not +the case with the microphone. In the first place, +the carbon contact is effected in the latter instrument +on other carbons and not with platinum +disks, and these contacts are multiple. In the +second place, the pressure exerted on all the points +of contact is excessively slight, so that the resistances +can be varied in an infinitely greater ratio than in +Mr. Edison’s system; and for this very reason it +is possible to magnify the sounds. In the third +place, a microphone can be made of other substances +besides carbon. Finally, no vibrating disk +is needed to make the microphone act; the simple +medium of air is enough, so that it is possible to +work the instrument from some little distance.</p> + +<p>We do not therefore see the grounds for Mr. +Edison’s assertions, and especially for the way in +which he has spoken of Messrs. Hughes and +Preece, who are well known in science and are in +all respects honourable men. I repeat my regret +that Mr. Edison should have made this ill-judged +attack on them, since it must injure himself, and is +unworthy of an inventor of such distinction. If we<span class="pagenum" id="Page_185">185</span> +look at the question from another point of view, +we must ask Mr. Edison why, if he invented the +microphone, he did not make us acquainted with +its properties and results. These results are indeed +startling, since the microphone has in so short a time +attracted general attention; and it is evident that +the clear-sighted genius of this celebrated American +inventor would have made the most of the discovery +if it were really his. The only justification for Mr. +Edison’s claim consists in his ignorance of the +purely scientific discoveries made in Europe, so +that he supposed the invention of the microphone +to be wholly involved in the principle which he +regards as his peculiar discovery.</p> + +<p>In Mr. Hughes’s instrument which we are now +considering, the sounds, instead of reaching the +receiving stations much diminished, which is the +case with ordinary telephones, and even with that +of Mr. Edison, are often remarkably increased, and +it is for this reason that Mr. Hughes has given to +this telephonic system the name of Microphone, +since it can be employed to discover very faint +sounds. Yet we must add that this increase really +takes place only when the sounds result from +mechanical vibrations transmitted by solid substances +to the sending instrument. The sounds +propagated through the air are undoubtedly a +little more intense than in the ordinary system, +but they lose some of their force, and therefore it +cannot be said that in this case the microphone<span class="pagenum" id="Page_186">186</span> +has the same effect upon sounds as the microscope +has on objects on which light is thrown. It is true +that with this system it is possible to speak at a +distance from the instrument, and I have even been +able to transmit conversation in a loud voice, when +standing at a distance of nine yards from the +microphone. When close to the instrument, I was +also perfectly able to make myself heard at the +receiving station while speaking in a low voice, and +even to send the sounds to a distance of ten or +fifteen centimètres from the mouthpiece of the +receiving telephone by raising the voice a little; +but the increase of sound is not really very evident +unless it is produced by a mechanical action transmitted +to the standard of the instrument.</p> + +<p>Thus the steps of a fly walking on the stand +are clearly heard, and give the sensation of a +horse’s tread; and even a fly’s scream, especially at +the moment of death, is said by Mr. Hughes to be +audible. The rustling of a feather or of a piece of +stuff on the board of the instrument, sounds +completely inaudible in ordinary circumstances, are +distinctly heard in the microphone. It is the same +with the ticking of a watch placed upon the +stand, which may be heard at ten or fifteen +centimètres from the receiver. A small musical +box placed upon the instrument gives out so +much sound, in consequence of its vibratory +movements, that it is impossible to distinguish the +notes, and in order to do so it is necessary to<span class="pagenum" id="Page_187">187</span> +place the box close to the instrument, without +allowing it to come in contact with any of its +constituent parts. It therefore appears that the +instrument is affected by the vibrations of air, and +the transmitted sounds are fainter than those heard +close to the box. On the other hand, the +vibrations produced by the pendulum of a clock, +when placed in communication with the standard +of the instrument by means of a metallic rod, are +heard perfectly, and may even be distinguished +when the connection is made by the intervention of +a copper wire. A current of air projected on the +system gives the sensation of a trickle of water heard +in the distance. Finally, the rumbling of a carriage +outside the house is transformed into a very intense +crackling noise, which may combine with the ticking +of a watch, and will often overpower it.</p> + +<p><i>Different Systems of Microphones.</i>—The microphone +has been made in several ways, but the one +represented in <a href="#il_39">fig. 39</a> is the arrangement which +renders it the most sensitive. In this system, two +small carbon cubes, <span class="allsmcap">A</span>, <span class="allsmcap">B</span>, are placed one above the +other on a vertical wooden prism; two holes are +pierced in the cubes to serve as sockets for a spindle-shaped +carbon pencil, that is, with the points fined +off at the two ends, and about four centimètres +long: if of a large size, the inertia will be too +great. One end of this pencil is in the cavity of +the lower carbon, and the other must move freely +in the upper cavity which maintains it in a position<span class="pagenum" id="Page_188">188</span> +approaching to that of instable equilibrium, that +is, in a vertical position. Mr. Hughes states that the +carbons become more effective if they are steeped +in a bath of mercury at red heat, but they will act +well without undergoing this process. The two +carbon cubes are also provided with metallic contacts +which admit of their being placed in connection +with the circuit of an ordinary telephone in +which a Leclanché battery has been placed, or one, +two, or three Daniell cells, with an additional resistance +introduced into the circuit.</p> + +<figure id="il_39" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p188.jpg" width="789" height="895" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 39.</span> + </figcaption> +</figure> + +<p><span class="pagenum" id="Page_189">189</span></p> + +<p>In order to use this instrument, it is placed on +a table, with the board which serves to support it, +taking care to deaden any extraneous vibrations +by interposing between this board and the table +several folds of stuff so arranged as to form a +cushion, or, which is better, a belt of wadding, or +two caoutchouc tubes: what is said by a person +standing before this system is immediately reproduced +in the telephone, and if a watch is placed on +the stand, or a box with a fly enclosed in it, all +its movements are heard. The instrument is so +sensitive that words said in a low voice are most +easily heard, and it is possible, as I have already +said, to hear the speaker when he is standing +nine yards from the microphone. Yet some precautions +are necessary in order to obtain good +results with this system, and besides the cushions +placed beneath the instrument to guard it from the +extraneous vibrations which might ensue from any +movements communicated to the table, it is also +necessary to regulate the position of the carbon +pencil. It must always rest on some point of the +rim of the upper cavity; but as the contact may be +more or less satisfactory, experience alone will +show when it is in the best position, and it is a +good plan to make use of a watch to ascertain +this. The ear is then applied to the telephone, +and the pencil is placed in different positions until +the maximum effect is obtained. To avoid the +necessity of regulating the instrument in this way,<span class="pagenum" id="Page_190">190</span> +which must be done repeatedly by this arrangement, +MM. Chardin and Berjot, who are ingenious +in the construction of telephones on this +pattern, have added to it a small spring-plate, of +which the pressure can be regulated, and which +rests against the carbon pencil itself. This system +works well.</p> + +<figure id="il_40" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p190.jpg" width="1009" height="667" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 40.</span> + </figcaption> +</figure> + +<p>M. Gaiffe, by constructing it like a scientific +instrument, has given the instrument a more elegant +form. <a href="#il_40">Fig. 40</a> represents one of his two models. +In this case, the cubes or carbon dice are supported +by metallic holders, and the upper one <span class="allsmcap">E</span> is made +to move up and down a copper column <span class="allsmcap">G</span>, so as to be +placed in the right position by tightening the screw <span class="allsmcap">V</span>.<span class="pagenum" id="Page_191">191</span> +In this way the carbon pencil can be made to +incline more or less, and its pressure on the upper +carbon can be altered at pleasure. When the pencil +is in a vertical position, the instrument transmits +articulate sounds with difficulty, on account of the +instability of the points of contact, and rustling +sounds are heard. When the inclination of the +pencil is too great, the sounds are purer and more +distinct, but the instrument is less sensitive. The +exact degree of inclination should be ascertained, +which is easily done by experiment. In another +model M. Gaiffe substitutes for the carbon pencil +a very thin square plate of the same material, +bevelled on its lower and upper surfaces, and revolving +in a groove cut in the lower carbon. This +plate must be only slightly inclined in order to +touch the upper carbon, and under these conditions +it transmits speech more loudly and distinctly.</p> + +<p>I must also mention another arrangement, devised +by Captain Carette of the French Engineers, +which is very successful in transmitting inarticulate +sounds. In this case the vertical carbon is pear-shaped, +and its larger end rests in a hole made in +the lower carbon; its upper and pointed end goes +into a small hole made in the upper carbon, but so +as hardly to touch it, and there is a screw to regulate +the distance between the two carbons. Under +such conditions, the contacts are so unstable that +almost anything will put an end to them, and consequently +the variations in the intensity of the<span class="pagenum" id="Page_192">192</span> +transmitted current are so strong that the sounds +produced by the telephone may be heard at the +distance of several yards.</p> + +<figure id="il_41" class="figcenter" style="max-width: 25em;"> + <img src="images/i_p192.jpg" width="964" height="771" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 41.</span> + </figcaption> +</figure> + +<p><a href="#il_41">Fig. 41</a> represents another arrangement, devised +by M. Ducretet. The two carbon blocks are +at <span class="allsmcap">D</span> <span class="allsmcap">D′</span>, the moveable carbon pencil is at <span class="allsmcap">C</span>, the telephone +at <span class="allsmcap">T</span>, and the binding screws at <span class="allsmcap">B</span> <span class="allsmcap">B′</span>. An +enlarged figure of the arrangement of the carbons +is given on the left. The arm which holds the +upper carbon <span class="allsmcap">D</span> is fastened to a rod, bearing a plate +<span class="allsmcap">P′</span>, of which the surface is rough, and a little cage +<span class="allsmcap">C′</span>, made of wire netting, can be placed upon the<span class="pagenum" id="Page_193">193</span> +plate, so as to enable us to study the movements +of living insects.</p> + +<p>When speech is to be transmitted with a force +which can make the telephone audible in a large +room, the microphone must have a special arrangement, +and <a href="#il_42">fig. 42</a> represents the one which Mr. +Hughes considers the most successful, to which +he has given the name of <em>speaker</em>.</p> + +<figure id="il_42" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p193.jpg" width="847" height="481" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 42.</span> + </figcaption> +</figure> + +<p>In this new form, the moveable carbon which is +required to produce the variable contacts is at <span class="allsmcap">C</span>, at +the end of a horizontal bar <span class="allsmcap">B A</span>, properly balanced +so as to move up and down on its central point. +The support on which the bar oscillates is fastened +to the end of a spring plate in order that it may +vibrate more easily, and the lower carbon is placed +at <span class="allsmcap">D</span> below the first. It consists of two pieces laid +upon each other, so as to increase the sensitiveness +of the instrument, and we represent the upper piece<span class="pagenum" id="Page_194">194</span> +at <span class="allsmcap">E</span>, which is raised so as to show that when it is +desired only one of these carbons need be used. +For this purpose the carbon <span class="allsmcap">E</span> is fastened to a +morsel of paper, which is fixed to the little board +and contributes to the articulation. A spring <span class="allsmcap">R</span>, of +which the tension can be regulated by the screw <i>t</i>, +serves to regulate the pressure of the two carbons. +Mr. Hughes recommends the use of metallised charcoal +prepared from deal.<a id="FNanchor_14" href="#Footnote_14" class="fnanchor">14</a> The whole is then enclosed +in a semi-cylindrical case <span class="allsmcap">H I G</span>, made of +very thin pieces of deal, and the system is fixed, +together with another similar system, in a flat box, +<span class="allsmcap">M J L I</span>, which, on the side <span class="allsmcap">M I</span>, presents an opening +before which the speaker stands, taking care to +keep his lower lip at a distance of two centimètres +from the bottom of the box. If the two telephones +are connected for strength, and if the battery +employed consists of two cells of bichromate of +potash, it is possible to act so strongly on the current, +that, after traversing an induction coil only +six centimètres long, a telephone of Bell’s square +model can be made to speak, so as to be heard +from all parts of a room; a speaking tube, about a +yard long, must indeed be applied to it. Mr. +Hughes asserts that the sounds produced by it are +nearly as loud as those of the phonograph, and +this is confirmed by Mr. Thomson.</p> + +<p><span class="pagenum" id="Page_195">195</span></p> + +<p>M. Boudet de Paris has lately invented a +microphone speaker of the same kind, with which +it is possible to make a small telephone utter a loud +sound. An induction coil, influenced by a single +Leclanché cell, must be employed.</p> + +<p>Suppose that a very small carbon rod with +pointed ends is placed at the bottom of a box, of +about the size of a watch. One end of the rod +rests against a morsel of carbon, which is fastened +to a very thin steel diaphragm, placed before a +mouthpiece which acts as a lid to the box, and is +screwed above it. Next suppose that a small piece +of paper, folded in two, in the shape of the letter +V, is fixed above that part of the carbon in contact +with the carbon of the diaphragm. This constitutes +the instrument, and in order to work it, it +must be held in a vertical position before the mouth, +at a distance of about three centimètres, and it is +necessary to speak in the ordinary tone. If the +telephone is placed in direct communication with +this instrument, it will send the voice to a distance. +Without employing a Leclanché cell, the voice +may be heard at the distance of ten yards, if one of +the carbons used for the phonograph is placed +before the mouthpiece of the telephone.</p> + +<p>In this system, the sensitiveness of the instrument +is entirely due to the slightness of the contact +between the two carbons, and the slight elasticity +of the folded paper constitutes the contact. Perhaps +the paper itself has some influence; at any rate the<span class="pagenum" id="Page_196">196</span> +most delicate spiral spring is incapable of producing +the same effect, and it is necessary to suspend the +instrument vertically, in order that the weight of +the moveable carbon may not affect it. It can be +regulated by depressing or elevating that part of +the paper which rests on the carbon rod.</p> + +<p>Although it is possible to work all telephones +with this instrument, some are more effective than +others. The mouthpiece must be concave, and the +diaphragm must be close to its rim, and must be +made of a particular kind of tin. The ordinary +diaphragm does not act well, and M. Boudet de +Paris has tried several, so as to obtain the maximum +effect.</p> + +<p>It is certain that when the instruments are as +well regulated as those which the inventor has +deposited with me, their results are really surprising. +It is even possible, by using several microphones at +the sending station, to obtain the reproduction of +duets, and even of trios, with remarkable effect.</p> + +<p>With this kind of microphone speaker M. +Boudet de Paris is able to transmit speech into a +snuff-box telephone, merely consisting of a flat +helix of wire, placed before a slightly magnetised +steel plate, and without insertion of a magnetic +core. A single Leclanché cell was enough. An +experiment of the same nature was tried in England, +but it was found necessary to use six Leclanché +cells.</p> + +<figure id="il_43" class="figcenter" style="max-width: 17em;"> + <img src="images/i_p197.jpg" width="643" height="347" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 43</span> + </figcaption> +</figure> + +<figure id="il_44" class="figcenter" style="max-width: 25em;"> + <img src="images/i_p197b.jpg" width="965" height="371" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 44.</span> + </figcaption> +</figure> + +<p>The microphone may also be made of morsels<span class="pagenum" id="Page_197">197</span> +of carbon pressed into a box between two metallic +electrodes, or enclosed in a tube with two electrodes +represented by two elongated fragments of carbon. +In the latter case the carbons ought to be as cylindrical +as possible, and those made by M. Carré for +the Jablochkoff candles are very suitable. <a href="#il_43">Fig. 43</a> +represents an instrument of this kind which M. +Gaiffe arranged for me, and which, as we shall see, +serves as a thermoscope (<a href="#il_44">fig. 44</a>). It is composed +of a quill filled with morsels of carbon, and those +at the two ends are tipped with metal. One of +these metal tips ends in a large-headed screw which, +by means of its supports <span class="allsmcap">A B</span>, is able to press more +or less on the morsels of carbon in the tube, and +consequently to establish a more or less intimate<span class="pagenum" id="Page_198">198</span> +contact between them. When the instrument is +properly regulated, speech can be reproduced by +speaking above the tube. It is therefore a microphone +as well as a thermoscope. Mr. Hughes has +remarked one curious fact, namely, that if the different +letters of the alphabet are pronounced separately +before this sort of microphone, some of them +are much more distinctly heard than others, and it +is precisely those which correspond to the breathings +of the voice.</p> + +<p>A microphone of this kind may be made by +substituting for the carbon powders of more or +less conductivity, or even metal filings. I have +shown in my paper on the action of substances of +moderate conductivity, that such power varies considerably +with the pressure and the temperature; +and as the microphone is based on the differences +of conducting power which result from differences +of pressure, we can understand that these powders +may be used as a means of telephonic transmission. +In a recent arrangement of this system Mr. Hughes +has made the powder adhere together with a sort +of gum, and has thus made a cylindrical pencil +which, when connected with two electrodes which +are good conductors, can produce effects analogous +to those we have just described. As I have said, +it is possible to use metal filings, but Mr. Hughes +prefers powdered charcoal.</p> + +<p>Mr. Blyth states that a flat box, about 15 inches +by 9, filled with coke, and with two tin electrodes<span class="pagenum" id="Page_199">199</span> +fixed to the two ends, is one of the best arrangements +for a microphone. He says that three of +these instruments, hung like pictures against the +wall of a room, would suffice, when influenced +by a single Leclanché cell, to make all the sounds +produced in a telephone audible, and especially +vocal airs. Mr. Blyth even asserts that a microphone +capable of transmitting speech can be made +with a simple piece of coke, connected with the +circuit by its two ends, but it must be coke: a retort +carbon, with electrodes, will not act.</p> + +<p>It is a remarkable property of these kinds of +microphones that they can act without a battery, +at least when they are so arranged as to form a +voltaic element for themselves, and this can be +done by throwing water on the carbons. Mr. Blyth, +who was the first to speak of this system, does not +distinctly indicate its arrangement, and we may +assume that his instrument did not differ from the +one we have already described, to which water +must have been added. In this way, indeed, I have +been able to transmit not only the ticking of a +watch and the sounds of a musical box, but speech +itself, which was often more distinctly expressed +than in an ordinary microphone, since it was free +from the sputtering sound which is apt to accompany +the latter. Mr. Blyth also asserts that sounds +may be transmitted without the addition of water, +but in this case he considers that the result is due +to the moisture of the breath. Certainly much<span class="pagenum" id="Page_200">200</span> +moisture is not required to set a voltaic couple in +action, especially when a telephone is the instrument +of manifestation. The ordinary microphone +may be used without a battery, if the circuit in +which it is inserted is in communication with the +earth by means of earthen cakes; the currents +which then traverse the circuit will suffice to make +the tickings of a watch placed upon the microphone +perfectly audible. M. Cauderay, of Lausanne, +in a paper sent to the Académie des Sciences, +July 8, 1878, informs us that he made this experiment +on a telegraphic wire which unites the Hôtel +des Alpes at Montreux with a <i lang="fr">châlet</i> on the hill—a +distance of about 550 yards.</p> + +<p><i>The Microphone used as a Speaking Instrument.</i>—The +microphone can not only transmit speech, +but it can also under certain conditions reproduce +it, and consequently supply the place of the receiving +telephone. This seems difficult to understand, +since a cause for the vibratory motion +produced in part of the circuit itself can only be +sought in the variations in intensity of the current, +and the effects of attraction and magnetisation have +nothing to do with it. Can the action be referred +to the repulsions reciprocally exerted by the contiguous +elements of the same current? Or are we +to consider it to be of the same nature as that +which causes the emission of sounds from a wire +when a broken current passes through it, so that +an electric current is itself a vibratory current, as<span class="pagenum" id="Page_201">201</span> +Mr. Hughes believes? It is difficult to reply to +these questions in the present state of science; we +can only state the fact, which has been published +by Messrs. Hughes, Blyth, Robert Courtenay, and +even by Mr. Edison himself. I have been able to +verify the fact myself under the experimental conditions +indicated by Mr. Hughes, but I was not so +successful in the attempt to repeat Mr. Blyth’s experiments. +This gentleman stated that in order to +hear speech in a microphone it would be enough to +use the model made from fragments of carbon, as +we have described, to join to it a second microphone +of the same kind, and to introduce into the circuit +a battery consisting of two Grove elements. If +anyone then speaks above the carbons of one of +the microphones, what is said should be distinctly +heard by the person who puts his ear to the other, +and the importance of the sounds thus produced +will correspond with the intensity of the electric +source employed. As I have said, I was unable +by following this method to hear any sound, still +less articulate speech; and if other experiments had +not convinced me, I should have doubted the correctness +of the statement. But this negative experiment +does not in fact prove anything, since it +is possible that my conditions were wrong, and that +the cinders which I employed were not subject to +the same conditions as Mr. Blyth’s fragments of +coke.</p> + +<figure id="il_45" class="figcenter" style="max-width: 15em;"> + <img src="images/i_p202.jpg" width="564" height="737" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 45.</span> + </figcaption> +</figure> + +<p>With respect to Mr. Hughes’s experiments, I<span class="pagenum" id="Page_202">202</span> +have repeated them with the microphone made by +MM. Chardin and Berjot, using that by M. Gaiffe +as the sender, and I ascertained that with a battery +of only four Leclanché cells, a scratch made +on the sender, and even the tremulous motion +and the airs played in a little musical box placed +on the sender, were reproduced—very faintly, +it is true—in the second microphone; in order +to perceive them, it was enough to apply the ear +to the vertical board of the instrument. It is true +that speech was not reproduced, but of this Mr. +Hughes had warned me; it was evident that with<span class="pagenum" id="Page_203">203</span> +this arrangement the instrument was not sufficiently +sensitive.</p> + +<p>A different arrangement of the microphone is +required for the transmission and the reproduction +of speech by this system, and a section of the one +which Mr. Hughes found most successful is given +in <a href="#il_45">fig. 45</a>. It somewhat resembles Mr. Hughes’s +microphone speaker, placed in a vertical position, +and the fixed carbon is fastened to the centre of +the stretched membrane of a string telephone. +The ear or mouth tube is at <span class="allsmcap">A</span>, the membrane at +<span class="allsmcap">D D</span>, the carbon just mentioned at <span class="allsmcap">C</span>: this carbon is of +metallised charcoal prepared from deal, and so also is +the double carbon <span class="allsmcap">E</span>, which is in contact with it and is +fastened to the upper end of the little bar <span class="allsmcap">G I</span>. +The whole is enclosed in a small box, and the +pressure exerted on the contact of the two carbons is +regulated by a spring <span class="allsmcap">R</span> and a screw <span class="allsmcap">H</span>. The tube +of the telephone serves as an acoustic tube for +the listener, and Mr. Hughes’s speaker, described +above, acts as sender. It is hardly necessary to say +that the two instruments are placed at each end of +the circuit, that the carbons are connected with the +two poles of a battery of one or two cells of bichromate +of potash, or two Bunsen or six Leclanché cells, +and the two instruments are connected by the line +wire. Under such conditions, conversation may be +exchanged, but the sounds are always much less +distinct than they are in a telephone.</p> + +<p>I was able to ascertain this fact with a roughly<span class="pagenum" id="Page_204">204</span> +made instrument brought from England by Mr. +Hughes. MM. Berjot, Chardin, and de Méritens, +who were also present at the experiments, were +able with me to hear speech perfectly, and I have +since successfully repeated the experiment alone, +but it does not always succeed, and under its present +conditions the instrument has no importance +in a scientific point of view. It is evident that the +instrument can dispense with any support, and the +little box then forms the handle of the instrument; +in this case the two binding screws are placed at the +end of this handle, as in a telephone. The microphone +speaker with a disk, represented in <a href="#il_5">fig. 5</a>, +which acts as sender to the singing condenser, can +be used, when properly regulated, as a receiving +microphone. M. Berjot has obtained good results +from a little instrument of the same kind as that +in <a href="#il_45">fig. 45</a>, but with a metal diaphragm, and the +microphonic system consists of a cylindrical piece of +carbon resting on a small disk of the same substance, +which is galvanised and soldered to the +diaphragm. The whole is enclosed in a small +round box, with its upper part cut in the form of a +mouthpiece.</p> + +<p>It seems that all microphone senders with disks +can reproduce speech more or less perfectly; it is +a question of adjusting and refining the carbon +points of contact. A weak battery, consisting of a +single Leclanché cell, is better for these instruments +than a strong battery, precisely because<span class="pagenum" id="Page_205">205</span> +of the effects of oxidation and polarisation, which +are so energetically produced at these points of +contact when the battery is strong.</p> + +<p>The effects of the microphone receiver explain +the sounds, often very intense, produced by +the Jablochkoff candles when they are influenced +by electro-magnetic machines. These sounds +always vibrate in unison with those emitted by the +machine itself, and they result, as I have already +shown, from the rapid magnetisations and demagnetisations +which are effected by the machine. +These effects, observed by M. Marcel Deprez, +were particularly marked in M. de Méritens’ first +machines.</p> + +<p><i>Other Arrangements of Microphones.</i>—An arrangement +such as we have just described has +been employed by M. Carette to form an extremely +powerful microphone speaker. The only difference +is that the stretched membrane is replaced by +a thin metallic disk: he fastens one of the carbons +to the centre of this disk, and applies to it the +other carbon, which is pointed, and held by a +<i lang="fr">porte-carbon</i> with a regulating screw, so that the +pressure which takes place between the two carbons +may be regulated at pleasure. By this arrangement +speech may be heard at a distance from +the telephone. In other respects it resembles the +telephone sender represented in <a href="#il_5">fig. 5</a>.</p> + +<p>M. de Méritens has executed the system represented, +<a href="#il_45">fig. 45</a>, on a large scale, forming the tube<span class="pagenum" id="Page_206">206</span> +<span class="allsmcap">A B</span> of a zinc funnel a yard in length, and in this +way he has been able to magnify the sounds, so +that a conversation held in a low voice, three or +four yards from the instrument, has been produced +in a telephone with more sonorous distinctness. The +instrument was placed on the floor of the apartment, +with the opening of the funnel above, and +the telephone was in the cellars of the house.</p> + +<p>The form of the microphone has been varied +in a thousand ways, to suit the purposes to which +it was to be applied. In the ‘English Mechanic +and World of Science,’ June 28, 1878, we see the +drawings of several arrangements, one of which is +specially adapted for hearing the steps of a fly. It +is a box, with a sheet of straw paper stretched on +its upper part; two carbons, separated by a morsel +of wood, and connected with the two circuit wires, +are fastened to it, and a carbon pencil, placed +crosswise between the two, is kept in this position +by a groove made in the latter. A very weak +battery will be enough to set the instrument at +work, and when the fly walks over the sheet of +paper it produces vibrations strong enough to +react energetically on an ordinary telephone. +The instrument must be covered with a glass globe. +When a watch is placed on the membrane, with its +handle applied to the morsel of wood which divides +the two carbons, the noise of its ticking may be +heard through a whole room. Two carbon cubes +placed side by side, and only divided by a playing-card,<span class="pagenum" id="Page_207">207</span> +may also be used instead of the arrangement +of carbons described above. A semicircular +cavity, made in the upper part of the two carbons, +in which are placed some little carbon balls, +smaller than a pea and larger than a mustard seed, +will make it possible to obtain multiple contacts +which are very mobile and peculiarly fit for telephonic +transmissions. This arrangement has been +made by Mr. T. Cuttriss.</p> + +<p>Several other arrangements of microphones +have been devised by different makers and inventors, +such as those of Messrs. Varey, Trouvé, +Vereker, de Combettes, Loiseau, Lippens, de +Courtois, Pollard, Voisin, Dumont, Jackson, Paterson, +Taylor, &c., and they are more or less satisfactory. +The instruments of MM. Varey, Trouvé, +Lippens, and de Courtois are the most interesting, +and we will describe them.</p> + +<p>M. Varey’s microphone consists of a sounding +box of deal, mounted in a vertical position on a +stand, and two microphones are arranged on +either side of it, with vertical carbons united for +tension. A small Gaiffe cell of chloride of silver, +without liquid, is applied to the standard of the +instrument, and is enough to make it work perfectly. +This system is extremely sensitive.</p> + +<p>M. Trouvé’s microphones, represented in <a href="#il_46">figs. 46</a>, +<a href="#il_47">47</a>, <a href="#il_48">48</a>, are extremely simple, so that he is able +to sell them at a very moderate price. They +generally consist of a small vertical cylindrical<span class="pagenum" id="Page_208">208</span> +box, as we see in the figure, with disks of carbon +at its two ends, which are united by a carbon rod, +or by a metallic tube tipped with carbon. This +rod or tube turns freely in two cavities made in +the carbons, and the box, while acting as a sounding +box, becomes at the same time a prison for the +insects whose movements and noises are the objects +of study.</p> + +<figure id="il_46" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p208.jpg" width="805" height="433" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 46.</span> + </figcaption> +</figure> + +<p>These boxes may be suspended on a cross-bar +(<a href="#il_47">fig. 47</a>) by the two communicating wires, so as to be +completely insulated. In this case the ticking of a +watch placed upon the board, friction, and external +shocks are hardly heard, but on the other hand the +sound vibrations of the air alone are transmitted, +and they acquire great distinctness. We have often +repeated these experiments, and have always found +that the tones of the voice were perfectly preserved.</p> + +<p><span class="pagenum" id="Page_209">209</span></p> + +<p>The model represented <a href="#il_48">fig. 48</a> is still more +simple, and appears to be the latest development +of this kind of instrument. It consists of a stand +and a disk united by a central rod. The upper +disk moves round the central rod, and permits +the vertical carbon to assume any inclination +which is desired. It is evident that the instrument +will become less sensitive when the carbon +is more oblique.</p> + +<figure id="il_47" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p209.jpg" width="818" height="637" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 47.</span> + </figcaption> +</figure> + +<p>We must also mention a very successful microphone +devised by M. Lippens. It is a slightly +made box, like that of M. Varey, and on its +opposite faces there are applied, on two frames +left empty for the purpose, two thin plates of +hardened caoutchouc, in the centre of which inside<span class="pagenum" id="Page_210">210</span> +the box, two carbons are fastened, and on their +outer surface a half-sphere is hollowed.</p> + +<figure id="il_48" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p210.jpg" width="813" height="437" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 48.</span> + </figcaption> +</figure> + +<p>The interval between the two carbons hardly +amounts to two millimètres, and a carbon ball is +inserted into the two cavities which form its +spherical case. This ball is supported by a spiral +spring which can be extended more or less by means +of a wire wound on a windlass which is fixed +above the instrument, like the spring of an electric +telegraph instrument. By means of this spring, +the pressure of the carbon ball against the sides of +the cavity which contains it can be regulated at +pleasure, and the sensitiveness of the instrument +and its capacity for transmitting speech can be +adjusted. Under these conditions, the vibrations +of the caoutchouc plates directly affect the microphone, +and the currents of air have no influence +on it, so that the effects are more distinct. It is so +sensitive that it is best for the speaker to place<span class="pagenum" id="Page_211">211</span> +himself at the distance of at least 50 centimètres +from the instrument. M. Lippens’ instrument is a +pretty one, mounted on a wooden stand, which is +neatly turned.</p> + +<p>In order to put an end to the sputtering usual +in microphones, it occurred to M. de Courtois to +prevent any cessation of contact between the +carbons by keeping them close together, and to +effect the variations of resistance necessary for +articulate sounds by making them slide over each +other, so as to insert a shorter or longer portion of +the carbon in the circuit. For this purpose a +vibrating disk is placed in a vertical position in a +rigid frame, and a small conducting rod, terminated +by a pointed carbon, is applied to it, with this +carbon point resting on another flat piece of carbon +placed below it. Influenced by the vibrations of +the disk, the carbon point moves to and fro, effecting +more or less extensive contacts with the lower +carbon, and thus producing variations of resistance +which almost correspond to the range of +vibrations on the disk.</p> + +<p><i>Experiments made with the Microphone.</i>—I must +now mention the interesting experiments which led +Mr. Hughes to the invention of the remarkable +instrument of which we have spoken, as well as +those undertaken by other scientific men, either +from a scientific or a practical point of view.</p> + +<p>Believing that light and heat can modify the +conductivity of bodies, Mr. Hughes went on to<span class="pagenum" id="Page_212">212</span> +consider whether sound vibrations, transmitted to +a conductor traversed by a current, would not +also modify this conductivity by provoking the +contraction and expansion of the conducting molecules, +which would be equivalent to the shortening +or lengthening of the conductor thus affected. If +such a property existed, it would make it possible +to transmit sounds to a distance, since variations in +the conductivity would result from variations corresponding +to the intensity of the current acting on +the telephone. The experiment which he made +on a stretched metal wire did not, however, fulfil +his expectation, and it was only when the wire +vibrated so strongly as to break, that he heard a +sound at the moment of its fracture. When he +again joined the two ends of the wire, another +sound was produced, and he soon perceived that +imperfect contact between the two broken ends of +wire would enable him to obtain a sound. Mr. +Hughes was then convinced that the effects he +wished to produce could only be obtained with a +divided conductor, and by means of imperfect +contacts.</p> + +<p>He then sought to discover the degree of +pressure which it was most expedient to exert +between the two adjacent ends of the wire, and for +this purpose he effected the pressure by means of +weights. He ascertained that when the pressure +did not exceed the weight of an ounce on the +square inch at the point of connection, the sounds<span class="pagenum" id="Page_213">213</span> +were reproduced with distinctness, but somewhat +imperfectly. He next modified the conditions of the +experiment, and satisfied himself that it was unnecessary +to join the wires end to end in order to +obtain this result. They might be placed side by +side on a board, or even separated (with a conductor +placed crosswise between them), provided that the +conductors were of iron, and that they were kept in +metallic connection by a slight and constant pressure. +The experiment was made with three Paris points, +and arranged as it appears in <a href="#il_49">fig. 49</a>, and it has +since been repeated under very favourable conditions +by Mr. Willoughby Smith with three of the +so-called rat-tail files, which made it possible to +transmit even the faint sound of the act of +respiration.<a id="FNanchor_15" href="#Footnote_15" class="fnanchor">15</a></p> + +<figure id="il_49" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p213.jpg" width="871" height="525" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 49.</span> + </figcaption> +</figure> + +<p><span class="pagenum" id="Page_214">214</span></p> + +<p>He afterwards tried different combinations of +the same nature, which offered several solutions of +continuity, and a steel chain produced fairly good +results, but slight inflections, like those caused by +the <em>timbre</em> of the voice, were not reproduced, and +he tried other arrangements. He first sought to +apply metallic powders to the points of contact; +powdered zinc and tin, known in commerce under +the name of white bronze, greatly increased the +effects obtained; but they were unstable, on +account of the oxidation of the contacts; and it +was in seeking to solve this difficulty, as well as +to discover the most simple means of obtaining a +slight and constant pressure on the contacts, that +Mr. Hughes was led to the arrangement, previously +described, of carbons impregnated with mercury, +and he thus obtained the maximum effect.<a id="FNanchor_16" href="#Footnote_16" class="fnanchor">16</a></p> + +<p><span class="pagenum" id="Page_215">215</span></p> + +<p>Mr. Hughes considers that the successful effects +of the microphone depend on the number and +perfection of the contacts, and this is doubtless the +reason why some arrangements of the carbon +pencil in the instrument described above were +more favourable than others.</p> + +<p>In order to reconcile these experiments with +his preconceived ideas, Mr. Hughes thought that, +since the differences of resistance proceeding from +the vibrations of the conductor were only produced +when it was broken, the molecular movements were +arrested by the lateral resistances which were equal +and opposite, but that if one of these resistances +were destroyed, the molecular movement could be +freely developed. He considers that an imperfect +contact is equivalent to the suppression of one of +these resistances, and as soon as this movement +can take place, the molecular expansions and +contractions which result from the vibrations must +correspond to the increase or diminution of resistance +in the circuit. We need not pursue Mr. +Hughes’s theory further, since it would take too +long to develope it, and we must continue our +examination of the different properties of the +microphone.<a id="FNanchor_17" href="#Footnote_17" class="fnanchor">17</a></p> + +<p><span class="pagenum" id="Page_216">216</span></p> + +<p>Carbon, as we have said, is not the only +substance which can be employed to form the +sensitive organ of this system of transmission. +Mr. Hughes has tried other substances, including +those which are good conductors, such as metals. +Iron afforded rather good results, and the effect +produced by surfaces of platinum when it was +greatly subdivided was equal, if not superior, to +that furnished by the mercurised carbon. Yet +since the difficulty of making instruments with this +metal is greater, he prefers the carbon, which +resembles it in being incapable of oxidation.</p> + +<p>We have already said that the microphone may +be used as a thermoscope, in which case it must +have the special arrangement represented in <a href="#il_43">fig. 43</a>. +Under these conditions, heat, reacting on +the conductivity of these contacts, may cause +such variations in the resistance of the circuit that +the current of three Daniell cells will be annulled +by approaching the hand to the tube. In +order to estimate the relative intensity of the +different sources of heat, it will be enough to<span class="pagenum" id="Page_217">217</span> +introduce into the circuit of the two electrodes <span class="allsmcap">A</span> +and <span class="allsmcap">B</span>, <a href="#il_43">fig. 43</a>, a battery <span class="allsmcap">P</span>, of one or two Daniell +cells, and a moderately sensitive galvanometer +<span class="allsmcap">G</span>. For this purpose one of 120 turns will suffice. +When the deviation decreases, it shows that the +source of heat is superior to the surrounding atmosphere; +and conversely, that it is inferior when +the deviation increases. Mr. Hughes says that the +effects resulting from the intervention of sunshine +and shadow are shown on the instrument by considerable +variations in the deviations of the galvanometer. +Indeed it is so sensitive to the slightest +variations of temperature that it is impossible to +maintain it in repose.</p> + +<p>I have repeated Mr. Hughes’s experiments +with a single Leclanché cell, and for this purpose +I employed a quill, filled with five fragments +of carbon, taken from the cylindrical carbons +of small diameter which are made by M. Carré for +the electric light. I have obtained the results +which are mentioned by Mr. Hughes, but I ought +to say that the experiment is a delicate one. +When the pressure of the fragments of carbon +against each other is too great, the current traverses +them with too much force to allow the calorific +effects to vary the deviation of the galvanometer, +and when the pressure is too slight, the current +will not pass through them. A medium degree of +pressure must therefore be effected to ensure the +success of the experiment, and when it is obtained,<span class="pagenum" id="Page_218">218</span> +it is observed that on the approach of the hand to +the tube, a deviation of 90° will, after a few +seconds, diminish, so that it seems to correspond +with the approach or withdrawal of the hand. +But breathing produces the most marked effects, +and I am disposed to believe that the greater +or less deviations produced by the emission of +articulate sounds when the different letters of the +alphabet are pronounced separately, are due to +more or less direct emissions of heated gas from +the chest. It is certain that the letters which require +the most strongly marked sounds, such as A, F, H, +I, K, L, M, N, O, P, R, S, W, Y, Z, produce the +greatest deviations of the galvanometric needle.</p> + +<p>In my paper on the conductivity of such bodies +as are moderately good conductors, I had already +pointed out this effect of heat upon divided substances, +and I also showed that after a retrograde +movement, which is always produced at once, +a movement takes place in an inverse direction to +the index of the galvanometer when heat has been +applied for some instants, and this deviation is +much greater than the one which is first indicated.</p> + +<p>In a paper published in the ‘American Scientific +Journal,’ June 28, 1878, Mr. Edison gives some +interesting details on the application of his system +of a telephonic sender to measuring pressures, +expansions, and other forces capable of varying the +resistance of the carbon disk by means of greater +or less compression. Since his experiments on<span class="pagenum" id="Page_219">219</span> +this subject date from December 1877, he again +claims priority in the invention of using the microphone +as a thermoscope; but we must observe that +according to Mr. Hughes’s arrangement of his +instrument, the effect produced by heat is precisely +the reverse of the effect described by Mr. Edison. +In fact, in the arrangement adopted by the latter, +heat acts by increasing the conductivity acquired +by the carbon under the increased pressure produced +by the expansion of a body sensitive to heat: +in Mr. Hughes’s system, the effect produced by +heat is precisely the contrary, since it then acts +only on the contacts, and not by means of pressure. +Therefore the resistance of the microphone-thermoscope +is increased under the influence of +heat, instead of being diminished. This contrary +effect is due to the division of some substance +which is only a moderate conductor, and I have +shown that under such conditions these bodies, +when only slightly heated, always diminish the +intensity of the current which they transmit. I +believe that Mr. Edison’s arrangement is the best +for the thermoscopic instrument, and makes it +possible to measure much less intense sources of +heat. Indeed he asserts that by its aid the heat of +the luminous rays of the stars, moon, and sun may +be measured, and also the variations of moisture in +the air, and barometric pressure.</p> + +<p>This instrument, which we give <a href="#il_50">fig. 50</a>, with +its several details, and with the rheostatic arrangement<span class="pagenum" id="Page_220">220</span> +employed for measuring, consists of a +metallic piece <span class="allsmcap">A</span> fixed on a small board <span class="allsmcap">C</span>, and on +one of its sides there is the system of platinum +disks and carbons shown in <a href="#il_28">fig. 28</a>. A rigid piece +<span class="allsmcap">G</span>, furnished with a socket, serves as the external +support of the system, and into this socket is +introduced the tapering end of some substance +which is readily affected by heat, moisture, or +barometric pressure. The other extremity is +supported by another socket <span class="allsmcap">I</span>, fitted to a screw-nut +<span class="allsmcap">H</span>, which may be more or less tightened by a +regulating screw. If this system is introduced into +a galvanometric circuit <i>a, b, c, i, g</i>, provided with +all the instruments of the electric scale of measure, +the variations in length of the substance inserted +are translated by greater or less deviations of the +galvanometric needle, which follow from the differences +of pressure resulting from the lengthening +or shortening of the surface capable of expansion +which is inserted in the circuit.</p> + +<figure id="il_50" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p221.jpg" width="939" height="1290" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 50.</span> + </figcaption> +</figure> + +<p>The experiments on the microphone made in +London at the meeting of the Society of Telegraphic +Engineers on May 25, 1878, were wonderfully +successful, and they were the subject of an +interesting article in the ‘Engineer’ of May 31, +which asserts that the whole assembly heard the +microphone speak, and that its voice was very like +that of the phonograph. When the meeting was +informed that these words had been uttered at +some distance from the microphone, the Duke of<span class="pagenum" id="Page_221">221</span> +Argyll, who was present, while admiring the important +discovery, could not help exclaiming that +this invention might have terrible consequences, +since, for instance, if one of Professor Hughes’s<span class="pagenum" id="Page_222">222</span> +instruments were placed in the room in Downing +Street, in which Her Majesty’s ministers hold their +cabinet council, their secrets might be heard in the +room in which the present meeting took place. +He added that if one of these little instruments +were in the pocket of Count Schouvaloff, or of +Lord Salisbury, we should at once be in possession +of the secrets for which all Europe was anxiously +waiting. If these instruments were able to repeat +all the conversations held in the room in which they +stood, they might be really dangerous, and the +Duke thought that Professor Hughes, who had +invented such a splendid yet perilous instrument, +ought next to seek an antidote for his discovery. +Dr. Lyon Playfair, again, thought that the microphone +ought to be applied to the aërophone, so +that by placing these instruments in the two Houses +of Parliament, the speeches of great orators might +be heard by the whole population within five or six +square miles.</p> + +<p>The experiments lately made with the microphone +at Halifax show that the Duke of Argyll’s +predictions were fully justified. It seems that a +microphone was placed on a pulpit-desk in a church +in Halifax, and connected by a wire about two +miles long with a telephone placed close to the bed +of a sick person, who was able to hear the prayers, +the chanting, and the sermon. This fact was communicated +to me by Mr. Hughes, who heard it +from a trustworthy source, and it is said that<span class="pagenum" id="Page_223">223</span> +seven patients have subscribed for the expense of an +arrangement by which they may hear the church +services at Halifax without fatigue.</p> + +<p>The microphone has also lately been applied to +the transmission of a whole opera, as we learn from +the following account in the ‘Journal Télégraphique,’ +Berne, July 25, <span class="locked">1878:—</span></p> + +<p>‘A curious micro-telephonic experiment took +place on June 19 at Bellinzona, Switzerland. A +travelling company of Italian singers was to perform +Donizetti’s opera, “Don Pasquale,” at the theatre of +that town. M. Patocchi, a telegraphic engineer, +took the opportunity of making experiments on +the combined effects of Hughes’s carbon microphone +as the sending instrument, and Bell’s telephone +as the receiver. With this object he placed a +Hughes microphone in a box on the first tier, close +to the stage, and connected it by two wires, from +one to half a millimètre in thickness, to four Bell +receivers, which were placed in a billiard-room +above the vestibule of the theatre, and inaccessible +to sounds within the theatre itself. A small battery +of two cells, of the ordinary type used in the +Swiss telegraphic service, was inserted in the circuit, +close to the Hughes microphone.</p> + +<p>‘The result was completely successful. The +telephones exactly reproduced, with wonderful +purity and distinctness, the instrumental music of +the orchestra, as well as the voices of the singers. +Several people declared that they did not lose a<span class="pagenum" id="Page_224">224</span> +note of either, that the words were heard perfectly; +the airs were reproduced in a natural key, with +every variation, whether <i lang="la">piano</i> or <i lang="la">forte</i>, and several +amateurs assured M. Patocchi that by listening to +the telephone they were able to estimate the musical +beauty, the quality of the singers’ voices, and the +general effect of the piece, as completely as if they +had been among the audience within the theatre.</p> + +<p>‘The result was the same when resistances +equivalent to 10 kilomètres were introduced into +the circuit, without increasing the number of cells +in the battery. We believe that this is the first +experiment of the kind which has been made in +Europe, at least in a theatre, and with a complete +opera; and those who are acquainted with the +delicacy and grace of the airs in “Don Pasquale” will +be able to appreciate the sensitiveness of the combined +instruments invented by Hughes and Bell, +which do not suffer the most delicate touches of +this music to be lost.’</p> + +<p>Although experiments with the microphone are +of such recent date, they have been very various, +and among other curious experiments we learn +from the English newspapers that the attempt has +been made to construct an instrument on the same +principle as the telephone, which shall be sensitive +to the variations of light. It is known that some +substances, and particularly selenium, are electrically +affected by light, that is, that their conductivity +varies considerably with the greater or less<span class="pagenum" id="Page_225">225</span> +amount of light which is shed upon them. If, +therefore, a circuit in which a substance of this +nature is inserted, is abruptly subjected to a somewhat +intense light, the increase of resistance which +results from it ought to produce a powerful sound +in a telephone inserted in the circuit. This fact has +been verified by experiment, and Mr. Willoughby +Smith infers from it, as we have already suggested, +that the effects produced in the microphone +are due to variations of resistance in the circuit, +which are produced by more or less close contacts +between imperfect conductors.</p> + +<p>In order to obtain this effect under the most +favourable conditions, Mr. Siemens employs two +electrodes, consisting of network of very fine platinum +wire, fitting into each other like two forks, of +which the prongs are interlaced. These electrodes +are inserted between two glass plates, and a drop +of selenium, dropped in the centre of the two pieces +of network, connects them on a circular surface large +enough to establish sufficient conductivity in the +circuit. It is on this flattened drop that the ray of +light must be projected.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="APPLICATIONS_OF_THE_MICROPHONE"><span id="toclink_225"></span>APPLICATIONS OF THE MICROPHONE.</h2> +</div> + +<p>The applications of the microphone increase +in number every day, and in addition to those of +which we have just spoken, there are others of +really scientific and even of practical interest. +Among the number is the use which can be made<span class="pagenum" id="Page_226">226</span> +of it as a system of relays for telegraphy, in +science for the study of vibrations imperceptible to +our senses, in medicine and surgery, and even in +manufactures.</p> + +<p><i>Its application to Scientific Research.</i>—We have +seen that several physicists, including Messrs. +Spottiswoode, Warwick, Rossetti, Canestrelli, +Wiesendanger, Lloyd, Millar, Buchin, and Blyth, +have been able to hear what is said in a telephone +which has no iron diaphragm, but it was so difficult +to establish the fact that it has been often disputed. +More certain evidence was desirable, and the +microphone is an opportune agent for affording it.</p> + +<p>The ‘Telegraphic Journal’ of September 1, 1878, +observes that M. du Moncel, in order to claim the +victory in his controversy with Colonel Navez, +had still to show that the sounds which appeared +to be inarticulate in telephones without a diaphragm +might become intelligible if they were +intensified. This has been done for him by the +use of Mr. Hughes’s microphone, and the following +experiments were made for the purpose.</p> + +<p>1. If a magnetising coil, surrounding a bar of +soft iron, is inserted in the circuit of a microphone, +with a battery of three cells, the ticking of a +watch and other sounds of the same kind may be +heard on approaching the ear to the electro-magnet +which has been thus constituted. It is true +that these sounds are very faint when they are +not amplified, but if the electro-magnet is fastened<span class="pagenum" id="Page_227">227</span> +to a board, and a second microphone is fixed to the +same board, the sounds produced by the electro-magnet +are magnified, and become distinctly audible +in the telephone which is placed in connection with +this second microphone.</p> + +<p>2. These sounds may be further amplified by +resting one of the extremities of the core of the +electro-magnet on one of the poles of a permanent +magnet, which is fixed upon the board. Articulate +speech may then be heard in the telephone which +is placed in connection with the microphone resting +on the board, and the point at issue between +MM. Navez and Du Moncel is completely decided +in this way: for the auxiliary microphone can +only propagate and amplify the vibration of +articulate sounds, which are communicated by +the bar magnet of the coil to the board on which +the two instruments are placed. In this way it +would be possible to render articulate sounds perceptible +to M. Navez, when transmitted by the +bar magnet of a telephone without a diaphragm.</p> + +<p>3. When a second bar magnet rests on the +free pole of the electro-magnet, so as to present to +it a pole of the same nature as the one with which +it is already in communication—in a word, if a bar +is placed between the two poles of a horseshoe +electro-magnet, the effects are still more marked, +and hence it may be assumed that the bar reacts +as an armature, by concentrating the lines of magnetic +force in the vicinity of the helix.</p> + +<p><span class="pagenum" id="Page_228">228</span></p> + +<p>4. When the two poles of a horseshoe magnet +are inserted together inside a coil, their effects are +equally energetic, although by this arrangement +one of the poles might be expected to neutralise +the effect of the other: but the most important +effects have been obtained by placing an armature +of soft iron across the poles of the magnet which +has been already inserted in the coil. Under these +conditions articulate sounds are distinctly heard.</p> + +<p>These experiments were confirmed by Mr. F. +Varley, in a letter published in the ‘Telegraphic +Journal’ of September 15, 1878, and among the +fresh experiments mentioned by him, we will quote +those which he made with an iron tube inserted in +a helix, in which the two opposite poles of two bar +magnets are introduced. These poles are only +separated from each other by the interval of an +inch, so that the centre of the iron tube may be +strongly magnetised.</p> + +<p>Mr. Varley says that this last arrangement +reproduces the articulate sounds which issue from a +sending microphone, and this experiment is more +decisive than that of Professor Hughes, in which +case it might be supposed that the bar magnet, +resting on the polar end of an electro-magnetic +bar, was only a modification of the disk in the +Bell telephone, set in vibration by the alternate +currents passing through the helix, and that these +vibrations were communicated to the board, and +became sensible when enlarged by the microphone.<span class="pagenum" id="Page_229">229</span> +But such an objection cannot be alleged in the +case of the arrangement described above, for since +the sound is produced between the current passing +into the helix and the magnetic current of the bar, +it can only be the result of a vibration produced +by a disturbance of the reciprocal relations subsisting +between these two elements. Mr. Varley +adds that these experiments confirm M. du Moncel’s +researches, which have thrown considerable light +upon the causes which are at work in the action of +the speaking telephone, and with which we have +hitherto been imperfectly acquainted.</p> + +<p><i>Its application to Telephonic Relays.</i>—In February +1878, I first began to consider the mode of forming +telephonic relays, but I was checked by the discovery +that there was no vibration in the receiving +telephone, and I made the following communication +on the subject to the Académie des Sciences +on February 25:—‘If the vibrations of the disk in +the receiving telephone were the same as those of +the sending telephone, it is easy to see that if a +telephone with a local battery, acting both as +sender and receiver, were substituted for the receiving +telephone, it might, by the intervention of +the induction coil, act as a relay, and might therefore +not only amplify the sound, but also transmit +it to any distance. It is, however, doubtful whether +the vibrations of the two corresponding disks are +of the same nature, and if the sound be due to +molecular contractions and expansions, the solution<span class="pagenum" id="Page_230">230</span> +of the problem becomes much more difficult. Here +is therefore a field for experiments.’ These experiments +have been successfully made by Mr. +Hughes, who acquainted me with them early in +June 1878, and they led to the discovery of a most +interesting system of microphonic relays.</p> + +<p>On a wooden board of moderate size, such as a +drawing board, he placed a microphone with a +carbon brought to a fine point at each end, and fixed +in a vertical position. One or more telephones were +placed in the circuit, with their membranes facing +the board, and a continuous sound was heard, +sometimes resembling a musical note, sometimes +the singing of boiling water in an oven; and the +sound, which could be heard at a distance, went +on indefinitely, as long as the electric force was exerted. +Mr. Hughes explains this phenomenon in +the following way.</p> + +<p>The slightest shock which affects the microphone +has the effect of sending currents, more or +less broken, through the telephones, which transform +them into sound vibrations, and since these +are mechanically transmitted by the board to +the microphone, they maintain and even amplify +its action, and produce fresh vibrations on the +telephones. Thus a fresh action is exerted on +the microphone, and so on indefinitely. Again, +if a second microphone, in connection with another +telephonic circuit, be placed upon the same +board, we have an instrument which acts as a<span class="pagenum" id="Page_231">231</span> +telephonic relay, that is, it transmits to a distance +the sounds communicated to the board, and these +sounds may serve either as a call, or as the elements +of a message in the Morse code, if a Morse +manipulator is placed in the circuit of the first +microphone. Mr. Hughes adds that he has made +several very successful experiments with this system +of instruments, although he only employed a +Daniell battery of six cells without any induction +coil. By fastening a pasteboard tube, 40 +centimètres in length, to the receiving telephone, +he was able to hear in all parts of a large room +the continuous sound of the relay, the ticking of a +watch, and the scratching of a pen upon paper. +He did not try to transmit speech, since it would +not have been reproduced with sufficient distinctness +under such conditions.</p> + +<p>Since this first attempt, Mr. Hughes has arranged +another and still more curious system of microphonic +relays, for which two microphones with +vertical carbons are required. He places two +microphones of this description on a board, and +connects one of them with a third microphone, +which acts as a sender, while the second is in communication +with a telephone and a second battery: +in this way the words uttered before the sender are +heard in the telephone, without employing any +electro-magnetic organ for the telephonic relay.</p> + +<p>In August 1878, Messrs. Houston and Thomson +likewise arranged a system of telephonic relays<span class="pagenum" id="Page_232">232</span> +which only differs from that of Mr. Hughes in the +particular of having the microphone fixed on the +diaphragm of the telephone, and not on the board +beside it. The system consists of three vertical +microphones, which can be combined for tension or +quantity, according to the conditions for which they +are required. The model of this instrument was +represented in the ‘Telegraphic Journal’ of August +15, 1878, to which we must refer our readers, if +they wish for further information on the subject.</p> + +<p><i>Its application to Medicine and Surgery.</i>—The +extreme sensitiveness of the microphone suggested +its use for the observation of sounds produced +within the human body, so that it might serve as a +stethoscope for listening to the action of the lungs +and heart. Dr. Richardson and Mr. Hughes are +now busy in the attempt to carry out this idea, but +so far the result is not very satisfactory, although +they still hope to succeed. Meanwhile, M. Ducretet +has made a very sensitive stethoscopic microphone, +which we represent in <a href="#il_51">fig. 51</a>. It consists +of a carbon microphone <span class="allsmcap">C P</span>, with a simple contact, +of which the lower carbon <span class="allsmcap">P</span> is fitted to one of M. +Marais’ tambourines with a vibrating membrane <span class="allsmcap">T</span>. +This tambourine is connected with another <span class="allsmcap">T′</span>, by a +caoutchouc tube, which is to be applied to the +different parts of the body which demand auscultation, +and which is therefore termed the <i lang="fr">tambour +explorateur</i>. The sensitiveness of the instrument is +regulated by means of a counterpoise <span class="allsmcap">P O</span>, which is<span class="pagenum" id="Page_233">233</span> +screwed upon the arm of a bent lever, and to +this the second carbon <span class="allsmcap">C</span> is fixed. The extreme +sensitiveness of M. Marais’ tambourines in transmitting +vibrations is well known, and since their +sensitiveness is further increased by the microphone, +the instrument becomes almost too impressionable, +since it reveals all sorts of sounds, which +it is difficult to distinguish from each other. Such<span class="pagenum" id="Page_234">234</span> +an instrument can only be of use when entrusted +to experienced hands, and a special education of +the organ of hearing is needful, in order to turn it +to account.</p> + +<figure id="il_51" class="figcenter" style="max-width: 26em;"> + <img src="images/i_p233.jpg" width="1037" height="1065" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 51.</span> + </figcaption> +</figure> + +<p>In a work lately published by M. Giboux on +the application of the microphone to medicine, this +stethoscopic system is rather severely criticised, and +not without reason if, as M. Giboux asserts, it is +only sensitive to the movements which take place +on the surface of the body, and those which are +internal are either lost or altogether changed in +character. But without pronouncing on the improvements +which may ultimately be made in the +instrument, M. Giboux thinks that its most important +use in medical practice consists in its allowing +a certain number of students to observe with the +professor the different sounds of the body, to study +them with him in their different phases, and thus +to profit more readily by his teaching. A microphonic +circuit might bifurcate between several telephones, +so that each person might hear for himself +what is heard by others.</p> + +<p>The most important application of the instrument +to surgical purposes has lately been made by +Sir Henry Thompson, aided by Mr. Hughes, for +the examination of the bladder in cases of stone. +It enables him to ascertain the presence and +precise position of calculi, however small they may +be. For the purpose of research, he uses a sound, +made of a Maillechort rod, a little bent at the end,<span class="pagenum" id="Page_235">235</span> +and placed in communication with a sensitive +carbon microphone. When the sound is moved +about in the bladder, the rod comes in contact with +stony particles, even if they are no +larger than a pin’s head, and friction +ensues, producing in the telephone +vibrations which can be easily distinguished +from those caused by the +simple friction of the rod on the +soft tissues of the sides of the +bladder. The arrangement of the +instrument is shown in <a href="#il_52">fig. 52</a>. +The microphone is placed in the +handle which contains the sound, +and is the same as that given in +<a href="#il_42">fig. 42</a>, but of smaller size, and +the two conducting wires <i>e</i> which +lead to the telephone, issue from +the handle by the end <i>a</i> opposite +to that <i>bb</i> to which the sound <i>dd</i> +is screwed. As this instrument +is not intended to reproduce speech, +retort carbons instead of wood +carbons may be used.</p> + +<figure id="il_52" class="figright" style="max-width: 5em;"> + <img src="images/i_p235.jpg" width="223" height="1164" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 52.</span> + </figcaption> +</figure> + +<p>Some deaf people, whose sense +of hearing is not completely destroyed, +have been able to hear by +an expedient based upon the principle of the microphone. +For this purpose two telephones, connected +by a metallic crown, which is placed on the temples,<span class="pagenum" id="Page_236">236</span> +are applied to the ears of the deaf person, and the +telephones are placed in communication with a +battery microphone, which hangs to the end of a +double conducting wire. The deaf man keeps the +microphone in his pocket, and presents it as an +acoustic tube to the person who wishes to converse +with him. Mr. Hughes’s speaker, represented +<a href="#il_42">fig. 42</a>, is the one used.</p> + +<p><i>Various Applications.</i>—The microphone may be +used in many other ways, some of which are suggested +in the ‘English Mechanic’ of June 21, +1878. The article states that by means of this +instrument, engineers will be able to estimate the +effects of the vibrations caused on old and new +buildings by the passage of heavy loads; a soldier +will be able to discover the enemy’s approach when +he is several miles off, and may even ascertain +whether he has to do with artillery or cavalry; the +approach of ships to the neighbourhood of torpedoes +may be automatically heralded on the coast +by this means, so that an explosion may be produced +at the right moment.</p> + +<p>It has also been proposed to use the microphone +to give notice of an escape of gas in coal-mines. +The gas, in escaping from between the +seams of coal, makes a whistling noise, which might, +with the aid of the microphone and telephone, be +heard at the top of the shaft. Again, it has been +suggested that the microphone might be used as a +seismograph to reveal the subterranean noises<span class="pagenum" id="Page_237">237</span> +which generally precede earthquakes and volcanic +eruptions, and which would be much intensified by +this instrument. It might even be of use to Signor +Palmieri for his observations in the Vesuvius +Observatory.</p> + +<p>The microphone has also been used by Mr. +Chandler Roberts to render the diffusion of gaseous +molecules through a porous membrane sensible to +the ear.</p> + +<p>As might have been expected, the acclamation +with which Mr. Hughes’s invention was received +led to the assertion of other claims to priority, and +in addition to that of Mr. Edison, on which we +have already given our opinion, there are several +others, showing that if some microphonic effects +were discovered at different times before the date +of Mr. Hughes’s discovery, they could not have +been considered important, since they were not +even announced. Among the number was that of +Mr. Wentworth Lascelles Scott, specified in the +‘Electrician’ of May 25, 1878, and that of M. Weyher, +presented to the Société de Physique, Paris, +in June 1878. Another, made by M. Dutertre, is +of somewhat greater importance, for his experiments +were reported in the Rouen papers in +February of the same year: yet there is no just +ground for such claims, since the earliest date of +his experiments is subsequent to the experiments +first made by Mr. Hughes. These began early in +December 1877, and in January 1878 they were<span class="pagenum" id="Page_238">238</span> +exhibited to officials of the Submarine Telegraph +Company, as Mr. Preece declared in a letter addressed +to the several scientific men.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="EXTERNAL_INFLUENCE_ON_TELEPHONIC"><span id="toclink_238"></span>EXTERNAL INFLUENCE ON TELEPHONIC +TRANSMISSIONS.</h2> +</div> + +<p>The obstacles which occur in telephonic transmissions +proceed from three causes: 1. The intensity +of sound is diminished by the loss of current in +transmission—a loss which is much greater in the +case of induced currents than in those received from +a battery. 2. Confusion is caused by the influence of +adjacent currents. 3. The induction from one wire +to another. This last influence is much greater +than is usually supposed. If two perfectly insulated +wires are placed side by side, one in communication +with the circuit of an electric bell, and the +other with the circuit of a telephone, the latter +will repeat the sounds of the bell with an intensity +often great enough to act as a call without applying +the instrument to the ear. MM. Pollard and +Garnier, in their interesting experiments with the +induced currents of the Ruhmkorff coil, have +ascertained that in this way not merely sounds may +be obtained which correspond with the induced +currents resulting from the action of the primary +current, but also those which result from the action +of the secondary current on other helices, which +are termed currents of the second order. These<span class="pagenum" id="Page_239">239</span> +different reactions frequently cause the telephonic +transmissions made on telegraphic lines to be disturbed +by irregular sounds, arising from the electric +transmissions on adjoining lines; but it does not +appear that these influences altogether neutralise +each other, so that conversation held in the ordinary +way and a message sent in the Morse code may be +heard simultaneously.</p> + +<p>At the Artillery School, Clermont, a telephonic +communication has been established, for the sake +of experiments, between the school and the butts, +which are at a distance of about eight miles. Another +communication of the same kind has been +established between the Clermont Observatory and +the one at Puy-de-Dôme, which is nearly nine miles +from the former. These two lines are carried on +the same posts for a course of six miles, together with +an ordinary telegraphic wire, and for a distance of +330 yards there are seven other such wires. The two +telephonic wires are separated from each other by +a space of 85 centimètres. The following facts +have been observed under these conditions.</p> + +<p>1. The school telephone is perfectly able to +read off from their sound the Morse messages +which pass through the two adjacent telegraph +wires, and the ticking of the instrument does not +at all interfere with the vocal communication of +the telephone, nor render it inaudible.</p> + +<p>2. The two adjacent telegraphic lines, although +not in contact, confuse their messages together, and<span class="pagenum" id="Page_240">240</span> +it has sometimes been possible to hear messages +from Puy-de-Dôme at the school through the wire +which runs to the butts, although the distance +between the two lines is nowhere less than 85 +centimètres.</p> + +<p>These inconveniences have been in some degree +remedied by inserting strong resistances in the +circuit, or by putting the current to earth at some +distance from the telephonic stations.</p> + +<p>M. Izarn, Professor of Physics at the Lycée, +Clermont, holds that telephonic electric currents +may readily be turned aside by the earth, especially +if in the course of their passage they encounter +metallic conductors, such as gas or water pipes. +He writes as follows on the subject, in a paper +addressed to the Académie des Sciences, on May +13, 1878:—‘I set up a telephone in the Clermont +Lycée with a single wire, more than 50 yards in +length, which crosses the court-yard of the Lycée, +and goes from the laboratory, where it is suspended +to a gas-burner, to a room near the porter’s lodge, +where it is suspended to another gas-burner. +When I applied my ear to the telephone, I could +distinctly hear the telegraphic signals, Morse or +otherwise, which came either from the telegraph +office at Clermont, or from the telephone office +which was at work between the School of Artillery +and the butts below Puy-de-Dôme, a distance of +eight miles. I could overhear words, and especially +the military orders issued at the butts for the<span class="pagenum" id="Page_241">241</span> +purpose of being heard at the school. Yet my +wire is perfectly independent of those used for +signalling, and is even very remote from them; but +as the wires of the telegraph office and of the +School of Artillery go to earth at a little distance +from the gas-pipes, it is probable that this phenomenon +is caused by a diversion of the current produced +in my wire, by means of the earth and the +network of metal pipes.’</p> + +<p>Mr. Preece made the same remark in his notice +of ‘some physical points connected with the +telephone.’ Again, we read in the ‘Telegraphic +Journal’ of June 15, 1878, that in a telephonic +concert transmitted from Buffalo to New York, the +singers at Buffalo were heard in an office placed +outside the telegraphic circuit in which the transmission +was effected. On enquiry, it was ascertained +that the wire through which the telephonic +transmission took place, was at one point in its +course close to the one which directly transmitted +the musical sounds, but the distance between the +two wires was not less than ten feet.</p> + +<p>When the circuits are altogether metallic, there +is much less risk of confusion, and M. Zetzche +declares that sounds proceeding from other wires +are in this case little heard, and then only +momentarily, so that it is much more easy to hear +with this arrangement than with the one in +ordinary use. ‘It is not,’ he says, ‘the resistances +of the wire, but rather the diversions of the current<span class="pagenum" id="Page_242">242</span> +near the posts, which interfere with telephonic +correspondence on long lines above ground. This +was proved by the following experiments:—I +connected the telegraphic line from Dresden to +Chemnitz with a line from Chemnitz to Leipzig +(54 miles), which made a circuit of 103 miles, going +to earth at its two extremities. There was no +communication between Dresden and Leipzig, but +Leipzig and Dresden could communicate with +ease, in spite of the greater extent of line. I broke +the connection with earth, first at Leipzig, then +simultaneously at Leipzig and Dresden, and I +observed the following effects. When insulation +took place at Leipzig only, the telephone could be +heard at the stations of Dresden, Riesa, and +Wurzen; when the line was insulated at both ends, +the communication was good between the two +latter stations, but it was observed that at the +intermediate station the words spoken at Wurzen +were more distinctly heard than the words spoken +at Riesa were heard at Wurzen. Since the distance +from Wurzen to Leipzig is little more than half +that from Riesa to Dresden, there are consequently +nearly twice as many posts on the latter line, which +carry the currents to earth, and hence I conclude +that these diversions of current explain the +possibility of conversing on an insulated line, and +also why sounds are more distinctly heard at the +Riesa station in consequence of the greater intensity +of current still remaining on the line.’</p> + +<p><span class="pagenum" id="Page_243">243</span></p> + +<p>Some vibrations also result from the action of +currents of air on telegraphic wires, which produce +the humming sound so well known on some lines, +and these may also react on the telephone; but +they are in this case generally mechanically +transmitted, and they may be distinguished from +the others, if the sounds which ensue are heard +after the telephone is excluded from the circuit by +a break with a short circuit and after the communication +to earth established behind the telephone +has been broken.</p> + +<p>The induced reactions caused by the line wires +on each other are not the only ones which may be +observed on a telephonic circuit: every manifestation +of electricity near a telephone may produce +sounds of greater or less force. Of this we have +already given a proof in M. d’Arsonval’s experiments, +and others by M. Demoget demonstrate the +fact still more clearly. In fact, if a small bar +magnet provided with a vibrator be placed before +one of the telephones of a telephonic circuit, and +the vibrating plate of the telephone be removed, in +order to draw away the sound produced by the +vibrator, its humming noise may be distinctly +heard on the second telephone of the circuit; a +noise which attains its maximum when the two extremities +of the electro-magnet are at their nearest +point to the telephone without a diaphragm, and it +is at its minimum when this electro-magnet is +presented to it along its neutral line. M. Demoget<span class="pagenum" id="Page_244">244</span> +supposes that the action which is exerted in this +instance is that of a magnet exerting two inducing +actions which are opposite and symmetrical, with +a field limited by a double paraboloid and with an +axis, according to his experiments, which extended +55 centimètres beyond the magnetic core, and a +vertical diameter of 60 centimètres. He believes +that in this way it would be easy to telegraph on +the Morse system, and that, in order to do so, it +would only be necessary to apply a key to the inducing +electro-magnet.</p> + +<p>Mr. Preece points out three ways of overcoming +the difficulty presented by the induced reactions +caused by the wires on each other.</p> + +<p>1. By increasing the intensity of the transmitted +currents, so as to make them decidedly stronger +than the induced currents, and to reduce the +sensitiveness of the receiving telephone.</p> + +<p>2. To place the telephonic wire beyond the +range of induction.</p> + +<p>3. To neutralise the effects of induction.</p> + +<p>The first mode may be effected by Edison’s +battery system, and we have seen that it is very +successful.</p> + +<p>In order to put the second mode in practice, +Mr. Preece says that it would be necessary to +study the two kinds of induction which are +developed on telegraphic lines: electro-static +induction, analogous to that produced on submarine +cables, and electro-dynamic induction, resulting<span class="pagenum" id="Page_245">245</span> +from electricity in motion. In the former +case, Mr. Preece proposes to interpose between the +telephone wire and the other wires a conducting +body in communication with the earth, capable of +becoming a screen to the induction by itself absorbing +the electro-static effects. He says that this +might be accomplished by surrounding the telegraphic +wires adjacent to the telephonic wire with +a metallic envelope, and then plunging them in +water. He adds that the effects of static induction +are not completely destroyed in this way, since the +substance used is a bad conductor, but they are +considerably reduced, as he has proved by experiments +between Dublin, Holyhead, Manchester, and +Liverpool. In the second case, Mr. Preece admits +that an iron envelope might paralyse the electro-dynamic +effects produced by absorbing them, so +that if insulated wires were employed, covered with +an iron case, and communicating with the earth, the +two induced reactions would be annulled. We will +not follow Mr. Preece in his theory as to these +effects—a theory which seems to us open to question, +but we content ourselves with pointing out +his proposed mode of attenuation.</p> + +<p>In order to carry out the third expedient, it +might be thought that it would be enough to +employ a return wire instead of going to earth, for +under such conditions the currents induced on one +of the wires would be neutralised by those resulting +from the same induction on the second wire,<span class="pagenum" id="Page_246">246</span> +which would then act in an opposite direction; but +this mode would only be successful when there is +a very small interval between the two telephone +wires, and they are at a considerable distance from +the other wires. When this is not the case, and +they are all close together, as in submarine or +subterranean cables, consisting of several wires, +this mode is quite inefficient. A small cable, +including two conductors, insulated with gutta-percha, +may be successfully carried through the +air.</p> + +<p>The use of two conductors has the further +advantage of avoiding the inconvenience of stray +currents on the line and through the earth, which, +when the communications to earth are imperfect, +permit the line current to pass more or less easily +into the telephonic line.</p> + +<p>In addition to the disturbing causes in telephonic +transmission we have just mentioned, there +are others which are also very appreciable, and +among them are the accidental currents which are +continually produced on telegraphic lines. These +currents may proceed from several causes, at one +time from atmospheric electricity, at another from +terrestrial magnetism, at another from thermo-electric +effects produced upon the lines, at another +from the hydro-electric reactions produced on the +wires and disks in communication with the earth. +These currents are always very unstable, and +consequently they are likely, by reacting on the<span class="pagenum" id="Page_247">247</span> +transmitted currents, to modify them so as to +produce sounds upon the telephone. Mr. Preece +asserts that the sound proceeding from earth +currents somewhat resembles that of falling water. +The discharges of atmospheric electricity, even +when the storm is remote, produce a sound which +varies with the nature of the discharge. When it +is diffused and the clap takes place near at hand, +Dr. Channing, of Providence, U.S., says that the +sound resembles that produced by a drop of fused +metal when it falls into water, or, still more, that of +a rocket discharged at a distance: in this case it +might seem that the sound would be heard before +the appearance of the flash, which clearly shows +that the electric discharges of the atmosphere only +take place in consequence of an electric disturbance +in the air. Mr. Preece adds that a wailing +sound is sometimes heard, which has been compared +to that of a young bird, and which must +proceed from the induced currents which terrestrial +magnetism produces in the metallic wires when +placed in vibration by currents of air.</p> + +<p>M. Gressier, in a communication made to the +Académie des Sciences on May 6, 1878, has +spoken of some of these sounds, but he is totally +mistaken in the source to which he ascribes them.</p> + +<p>‘In addition to the crackling sound caused by +the working of telegraph instruments on the +adjacent lines, a confused murmur takes place in +the telephone, a friction so intense that it might<span class="pagenum" id="Page_248">248</span> +sometimes be thought that the vibrating disk was +splitting. This murmur is heard more by night +than by day, and is sometimes intolerable, since it +becomes impossible to understand the telephone, +although nothing is going on in the office to disturb +the sound. The same noise is heard when +only one telephone is used. A good galvanometer +inserted in the circuit reveals the presence of +sensible currents, sometimes in one direction, sometimes +in another.’</p> + +<p>I studied these currents for a long time with +the galvanometer, and made them the subject of +four papers which were laid before the Académie +des Sciences in 1872, and I am convinced that +they have in general nothing to do with atmospheric +electricity, but result either from thermo-electric +or hydro-electric influence. They take +place constantly and in all weathers on telegraph +lines, whether these lines are insulated at one end, +or in contact with the earth at both ends. In the +first case, the polar electrodes of the couple are +formed by the telegraph wire and the earth plate, +generally of the same nature, and the intermediate +conducting medium is represented by the posts +which support the wire and the earth which completes +the circuit. In the second case, the couple +is formed in almost the same way, but the difference +in the chemical composition of the ground at +the two points where the earth plates are buried, and +sometimes their different temperature, exert a<span class="pagenum" id="Page_249">249</span> +strong influence. If only the first case be considered, +it generally happens that on fine summer +days the currents produced during the day are +inverse to those which are produced by night, and +vary with the surrounding temperature in one or +the other direction. The presence or absence of +the sun, the passage of clouds, the currents of air +involve abrupt and strongly marked variations, +which may be easily followed on the galvanometer, +and which cause more or less distinct sounds in the +telephone.</p> + +<p>During the day, the currents are directed from +the telegraph line to the earth plate, because +the heat of the wire is greater than that of the +plate, and these currents are then thermo-electric. +During the night, on the other hand, the wire +is cooled by the dew, which causes a greater oxidation +on the wire than that which takes place on the +plate, and the currents then become hydro-electric.</p> + +<p>I say more about these currents because, in +consequence of a mistaken belief as to their origin, +it has been supposed that the telephone might +serve for the study of the variations of the atmospheric +electricity generally diffused through the air. +Such an application of the telephone would, under +these conditions, be not only useless, but also misleading, +by inducing the study of very complex +phenomena, which could lead to nothing more +than I have already stated in my different papers +on the subject.</p> + +<p><span class="pagenum" id="Page_250">250</span></p> + +<p>Certain local influences will also produce sounds +in the telephone. Thus the distension of the +diaphragm by the moist heat of the breath, when +the instrument is held before the mouth in speaking, +causes a perceptible murmur.</p> + +<p>From the electro-static reactions, so strongly +produced on the submarine cables, in consequence +of electric transmissions, it might be supposed +that it would not be easy to hold telephonic correspondence +through this kind of conductor, and, to +ascertain the fact, an experiment was made on the +cable between Guernsey and Dartmouth, a distance +of sixty miles. Articulate speech, only a little indistinct, +was, however, perfectly transmitted. Other +experiments, made by Messrs. Preece and Wilmot, +on an artificial submarine cable, placed in conditions +analogous to those of the Atlantic cable, +showed that a telephonic correspondence might be +kept up at a distance of a hundred miles, although +the effects of induction were apparent. At the distance +of 150 miles, it was somewhat difficult to hear, +and the sounds were very faint, as if some one were +speaking through a thick partition. The sound diminished +rapidly until the distance of 200 miles was +reached, and after that it became perfectly indistinct, +although singing could still be heard. It was +even possible to hear through the whole length of +the cable, that is, for 3,000 miles, but Mr. Preece +believed this to be due to the induction of the condenser +on itself: he holds, however, that singing<span class="pagenum" id="Page_251">251</span> +may be heard at a much greater distance than +speech, owing to the more regular succession of +electric waves.</p> + +<p>Mr. Preece also made experiments on the subterranean +telegraphs between Manchester and +Liverpool, a distance of 30 miles, and found no +difficulty in exchanging correspondence; and it +was the same with the cable from Dublin to Holyhead, +a distance of 67 miles. This cable had seven +conducting wires, and when the telephone was connected +with one of them, the sound was repeated +through all the others, but in a fainter degree. +When the currents of the telegraphic instruments +passed through the wires, the induction was apparent, +but not so great as to prevent telephonic +communication.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="ESTABLISHMENT_OF_A_TELEPHONIC_STATION"><span id="toclink_251"></span>ESTABLISHMENT OF A TELEPHONIC STATION.</h2> +</div> + +<p>Although the telephonic system of telegraphy +is very simple, yet certain accessory arrangements +are indispensable for its use. Thus, for example, +an alarum call is necessary, in order to know when +the exchange of correspondence is to take place, +and information that the call has been heard is +likewise necessary. An electric bell is therefore +an indispensable addition to the telephone, and +since the same circuit may be employed for both +systems, if a commutator is used, it was necessary +to find a mode of making the commutator act automatically,<span class="pagenum" id="Page_252">252</span> +so as to maintain the simple action of +the system which constitutes its principal merit.</p> + +<p><i>MM. Pollard and Garnier’s System.</i>—With +this object, MM. Pollard and Garnier devised a +very successful arrangement last March, which +employs the weight of the instrument to act upon +the commutator.</p> + +<p>For this purpose, they suspended the instrument +to the end of a spring plate, fastened between +the two contacts of the commutator. The circuit +wire corresponds with this plate, and the two contacts +correspond, the one with the telephone, the +other with the bell. When the telephone hangs +below the spring-support, that is, when it is not at +work, its weight lowers the spring plate on the +lower contact, and the communication of the line +with the bell is established: when, on the other +hand, the telephone is raised for use, the spring +plate touches the higher contact, and communication +is established between the line and telephone. +In order to make the bell sound, it is only +necessary to establish, on the wire which connects +the line with the bell contact of the commutator, +a breaker which can both join and break the +current, and which communicates on one side with +the contact of the bell, and on the other with +its battery. The ordinary push of an electric +bell will be sufficient, if it is supplied with a +second contact, but MM. Pollard and Garnier +wished to make this action also automatic, and consequently<span class="pagenum" id="Page_253">253</span> +they devised the arrangement represented in +<a href="#il_53">fig. 53</a>.</p> + +<figure id="il_53" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p253.jpg" width="916" height="623" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 53.</span> + </figcaption> +</figure> + +<p>In this system, as well as in those which have +since been devised, two telephones are employed, +one of which is constantly applied to the ear, and +the other to the mouth, so as to make it possible to +speak while listening. The telephones are supported +by three wires, two of which contain flexible conductors, +while the third only acts as a support.</p> + +<p>Two of the four wires of the two telephones are +connected with each other, and the other two are +connected with the two binding screws of the +commutator <i>t</i>, <i>t′</i>: the wires without conductors are +suspended to the extremities of the two flexible +plates <i>l</i>, <i>l′</i>, which correspond with earth and line.</p> + +<p><span class="pagenum" id="Page_254">254</span></p> + +<p>When at rest, the weight of the telephones +presses the two plates <i>l</i>, <i>l′</i>, on the lower contacts +<span class="allsmcap">S</span>, <span class="allsmcap">S′</span>, but when the instruments are taken up +these plates press against the higher contacts.</p> + +<p>The two bell wires terminate on the lower +contacts, those of the telephones on the higher contacts, +and one of the poles of the battery is +connected with the lower contact on the left <span class="allsmcap">S′</span>, the +other with the higher contact on the right <span class="allsmcap">T</span>.</p> + +<p>When at rest, the system is applied to the +electric bell, and the current sent from the opposite +station will follow the circuit <span class="allsmcap">L</span> <i>l</i> <span class="allsmcap">S S′ S′</span> <i>l′</i> <span class="allsmcap">T</span>, so that +the call will be made. On taking up the two +telephones, the circuit of the bell system is broken, +and that of the telephones is established, so that the +current follows the course <span class="allsmcap">L</span> <i>l</i> <span class="allsmcap">T</span> <i>t t′</i> <span class="allsmcap">T′</span> <i>l′</i> <span class="allsmcap">T</span>. If only +one telephone is held at a time, the current is sent +into the bell system of the opposite station, and +follows the route + <span class="allsmcap">P S</span> <i>l</i> <span class="allsmcap">L T</span> <i>l′</i> <span class="allsmcap">T′</span> <i>t</i> <span class="allsmcap">P</span> —. In this +way the three actions necessary for calling, corresponding, +and enabling the corresponding instrument +to give a call, are almost involuntarily made.</p> + +<p><i>System by MM. Bréguet and Roosevelt.</i>—In the +system established by the Paris agents of the Bell +company, the arrangement resembles the one just +described, except that there is only one spring +commutator, and the call is made with the push of +an ordinary electric bell. A mahogany board is +suspended from the wall, and on it are arranged, +first, the ordinary electric bell system, with a sending<span class="pagenum" id="Page_255">255</span> +push fixed below it; second, two forks supporting +two telephones, one of which is fastened to the<span class="pagenum" id="Page_256">256</span> +bar of a commutator, arranged as a Morse key. +The two telephones are connected by two conducting +wires, so arranged as to be capable of extension, +and two of their four binding screws are in immediate +connection with each other, and the other +two with the earth, line, and battery, by means of +the commutator, the sending push, and the bell +system. The arrangement is shown in <a href="#il_54">fig. 54</a>.</p> + +<figure id="il_54" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p255.jpg" width="967" height="1353" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 54.</span> + </figcaption> +</figure> + +<p>The commutator A consists of a metallic bar +<i>a c</i>, bearing the suspension fork of one of the telephones +<span class="allsmcap">F′</span> below its point of articulation: it ends in +two pins <i>a</i> and <i>c</i>, below which the two contacts of +the commutator are fixed, and a spring compresses +the lower arm of the bar, so as to cause +the other arm to rest constantly on the higher +contact. For greater security a steel tongue <i>a b</i> +is fastened to the lower end of the bar, and rubs +against the small shaft <i>b</i>, which is provided +with two insulated contacts, corresponding to +those of the board. The bar is in communication +with the line wire by means of the call-push, +and the upper of the two contacts we have just +described corresponds with one of the telephone +wires which is inserted in the same circuit, while +the other corresponds with the bell system <span class="allsmcap">S</span>, +which is in communication with earth. It follows +from this arrangement, that when the right telephone +presses its whole weight on the support, the +bar of the commutator is inclined on the lower +contact, and consequently the line is in direct<span class="pagenum" id="Page_257">257</span> +communication with the bell, so that the call can +be made. When, on the other hand, the telephone +is removed from its support, the bar rests on the +higher contact, and the telephones are connected +with the line.</p> + +<p>Pressure on the sending push serves to call the +corresponding station: the connection of the line +with the telephones is then broken, and it is +established with the battery of the sending station, +which sends its current through the bell of the +corresponding station. In order to obtain this +double effect, the contact spring of the sending +push generally rests upon a contact fastened to a +piece of wood shaped like a joiner’s rule, which +covers it in front, and below this spring there is a +second contact, which communicates with the positive +pole of the station battery. The other contact +corresponds with the line wire, and a connection +takes place between the earth wire and the negative +pole of the station battery, so that the earth wire +is common to three circuits:</p> + +<p>1st. To the telephone circuit. 2nd. To that of +the bell system. 3rd. To that of the local battery.</p> + +<p>The second fork, which supports the telephone +on the right, is fixed to the board, and is independent +of any electric current.</p> + +<p>It is clear that this arrangement may be varied +in a thousand ways, but the model we have just +described is the most practical.</p> + +<p><i>Edison’s System.</i>—The problem becomes more<span class="pagenum" id="Page_259">259</span> +complex in the case of battery telephones, since +the battery must be common to both systems, and +the induction coil must be inserted in two distinct +circuits. <a href="#il_55">Fig. 55</a> represents the model adopted in +Mr. Edison’s telephone.</p> + +<figure id="il_55" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p258.jpg" width="901" height="1493" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 55.</span> + </figcaption> +</figure> + +<p>In this arrangement, there is a small stand <span class="allsmcap">C</span> +on the mahogany board on which the bases of +the two telephones rest. The bell system <span class="allsmcap">S</span> is +worked by an electro-magnetic speaker <span class="allsmcap">P</span>, which +serves, when a Morse key is added to the system, +for exchange of correspondence in the Morse code, +if there should be any defect in the telephones, or +to put them in working order. Above the speaker +there is a commutator with a stopper <span class="allsmcap">D</span> to adapt +the line for sending or receiving, with or without +the bell; and below the stand <span class="allsmcap">C</span> the induction coil, +destined to transform the voltaic currents into +induced currents, is arranged in a small closed +box <span class="allsmcap">E</span>.</p> + +<p>When the commutator is at reception, the line is +in immediate correspondence either with the speaker +or with the receiving telephone, according to the +hole in which the stopper is inserted; when, on the +other hand, it is at sending, the line corresponds to +the secondary circuit of the induction coil. Under +these conditions the action is no longer automatic; +but since this kind of telephone can only be usefully +employed for telegraphy, in which case those +who work it are acquainted with electric apparatus, +there is no inconvenience in this complication.</p> +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_260">260</span></p> + +<h2 class="nobreak" id="CALL-BELLS_AND_ALARUMS"><span id="toclink_260"></span>CALL-BELLS AND ALARUMS.</h2> +</div> + +<p>The call-bells applied to telegraphic service +have been arranged in different ways. When the +vibrating bells are in use, like those of which we +have just spoken, it is necessary to use a battery, +and the advantages offered by telephones with +induced currents are thus sensibly diminished. In +order to dispense with the battery, the use of the +electro-magnetic bell has been suggested.</p> + +<p>In this case there are usually two bells, with a +hammer oscillating between them, and a support +formed of the polarised armature of an electro-magnet. +The electro-magnetic instrument is placed +below this system; it is turned by a winch, and +sends the currents, alternately reversed, which are +necessary to communicate the vibratory movement +to the hammer, and this movement is enough to +make the two bells tinkle. Below the winch of this +electro-magnetic instrument there is a commutator +with two contacts, which adapts the instrument +for sending or receiving.</p> + +<p>M. Mandroux has simplified this system, and +has reduced it to small dimensions by the following +arrangement. He fixes two magnetic cores, +furnished with coils, on each of the two poles of a +horseshoe magnet, composed of two bars connected +by an iron coupler, and between the +poles expanded by these four cores he inserts an<span class="pagenum" id="Page_261">261</span> +armature, within which there is a steel spring +fastened to one of these poles. In this way the +armature is polarised, and oscillates under the +influence of the reversed currents transmitted by +an instrument of the same kind provided with an +induction system. These oscillations may have +the effect of producing the sound of a call-bell, and +the induction system may consist of a manipulating +key, fastened to a duplex system of armature, +regularly applied to the magnetic cores, taken in +pairs. On communicating a series of movements +to this manipulator, a series of induced currents +in an inverse direction are produced, which cause +the armature of the corresponding station to act +as we have already seen, and which may even, +when necessary, furnish a series of Morse signals +for a suitable manipulation. On account of the +small size of this system, it might be applied to +the telephonic service of the army.</p> + +<p>The Bell Telephone Company in Paris has +arranged another little call-system which is quite +satisfactory and has the advantage of acting as a +telephone at the same time. The model resembles +the one we have termed a snuff-box telephone, +and it has a button commutator by means of +which the instrument is placed in communication +with the electro-magnetic system of the instrument, +or with a battery which is able to make the telephone +vibrate with some force. To make a call, +the button must be pressed, and the battery<span class="pagenum" id="Page_262">262</span> +current is communicated to the corresponding +instrument, which begins to vibrate when the call +is made; and when notice is given of the receipt of +the signal, the pressure on the button is removed, +and it becomes possible to speak and receive as in +ordinary telephones.</p> + +<figure id="il_56" class="figcenter" style="max-width: 29em;"> + <img src="images/i_p262.jpg" width="1122" height="851" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 56.</span> + </figcaption> +</figure> + +<p><i>M. de Weinhold’s System.</i>—M. Zetzche speaks +highly of an alarum devised by Professor A. de +Weinhold, which resembles that by M. Lorenz, +represented in <a href="#il_56">fig. 56</a>. Its organ of sound consists +of a steel bell <span class="allsmcap">T</span>, from 13 to 14 centimètres in<span class="pagenum" id="Page_263">263</span> +diameter, and toned to give about 420 double +vibrations in a second. ‘Its diameter and tone,’ he +says, ‘are important, and any great departure from +the rule laid down diminishes the effect. The +opening of the bell is below, and it is fixed on a +stand by its centre. A slightly curved bar magnet, +provided at its two ends with iron appendices enclosed +in a coil, traverses the stand. The bar +magnet of the telephone also terminates in an iron +appendix enclosed in a coil. In both cases the +changes produced in the magnetic condition appear +to be more intense than they are in magnets without +appendices. The bar magnet is placed within +the bell in the direction of one of its diameters, so +that the appendices almost touch its sides.</p> + +<p>‘When the bell is struck on a spot about 90° +from this diameter with a wooden clapper M, which +acts with a spring, and is withdrawn by stretching +the spring and then letting it go, as in a bell for +the dinner-table, the vibrations imparted to it send +currents into the coils, and these currents produce +identical vibrations on the iron disk of the telephone, +which are intensified by a conical resonator +fitted to the telephone, so as to be easily +heard some paces off. For ordinary use, the bell +coil is broken into a short circuit by means of a +metallic spring <span class="allsmcap">R</span>, and consequently, when the bell is +struck, the spring must be opened so as not to break +the circuit. An instrument of the same kind has +also been devised by Herr W. E. Fein at Stuttgardt.’</p> + +<p><span class="pagenum" id="Page_264">264</span></p> + +<figure id="il_57" class="figleft" style="max-width: 10em;"> + <img src="images/i_p264.jpg" width="399" height="553" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 57.</span> + </figcaption> +</figure> + +<figure id="il_58" class="figright" style="max-width: 10em;"> + <img src="images/i_p264r.jpg" width="397" height="553" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 58.</span> + </figcaption> +</figure> + +<p><i>MM. Dutertre and Gouault’s System.</i>—One of +the most ingenious solutions of the problem of +making the telephone call has recently been +proposed by MM. Dutertre and Gouault. <a href="#il_57">Figs. 57</a> +and <a href="#il_58">58</a> represent the opposite faces of the +instrument. It consists of a kind of snuff-box +telephone, like the one shown in <a href="#il_26">fig. 26</a>, and it is +so arranged as to send or receive the call, according +to the way in which it is placed on its stand, +which is only an ordinary bracket fastened to the +wall. When it is placed on the bracket so as to +have the telephone mouthpiece on the outside, it is +adapted for receiving, and can then give the call. +When, on the other hand, its position on the +bracket is reversed, it permits the other station to +make the call, by producing vibrations on a +vibrator under the influence of a battery, and<span class="pagenum" id="Page_265">265</span> +these vibrations reverberate in the corresponding +instrument with sufficient force to produce the call. +If the instrument is taken up, and the finger is +placed on a small spring button, it may then be +used as an ordinary telephone.</p> + +<p>In this instrument, the magnet <span class="allsmcap">N S</span> (<a href="#il_57">fig. 57</a>) is +snail-shaped, like others we have mentioned, but +the core of soft iron <span class="allsmcap">S</span>, to which the coil <span class="allsmcap">E</span> is +fastened, can produce two different effects on its +two extremities. On the one side, it reacts on a +small armature which is fastened to the end of a +vibrating disk <span class="allsmcap">C</span>, <a href="#il_58">fig. 58</a>; the armature is placed +against a contact fastened to the bridge <span class="allsmcap">B</span>, and +constitutes an electro-magnetic vibrator. For this +purpose the bridge is in metallic communication +with the coil wire, of which the other end corresponds +with the line wire, and the spring <span class="allsmcap">C</span> is +mounted on an upright <span class="allsmcap">A</span>, which also supports +another spring <span class="allsmcap">D G</span> acting on two contacts, one +placed at <span class="allsmcap">G</span>, and corresponding to the earth wire, +the other at <span class="allsmcap">H</span>, and connected with the positive +pole of the battery. A small moveable button, +which passes through a hole in the lid of the box, +and projects beyond it, is fixed at <span class="allsmcap">G</span>, and all this +part of the instrument faces the bottom of the box. +The upper part consists of the vibrating disk and +the mouthpiece, so that the mechanism we have +described is all mounted on an inner partition +forming a false bottom to the box.</p> + +<p>When the box rests upon its base, on the side<span class="pagenum" id="Page_266">266</span> +shown in <a href="#il_58">fig. 58</a>, the button at <span class="allsmcap">G</span> presses on the +spring <span class="allsmcap">D G</span>, and raises it so as to break the connection +with the battery; the coil of the instrument +is then united to the circuit, and consequently +receives the transmitted currents, which follow this +route: line wire, coil <span class="allsmcap">E</span>, bridge <span class="allsmcap">B</span>, spring <span class="allsmcap">C</span>, spring +<span class="allsmcap">D G</span>, earth contact. If these currents are transmitted +by a vibrator, they are strong enough to +produce a noise which can be heard in all parts of +a room, and consequently the call may be given in +this way. If the currents are due to telephonic +transmission, the instrument is applied to the ear, +care being taken to put the finger on the button <span class="allsmcap">G</span>, +and the exchange of correspondence takes place +as in ordinary instruments; but it is simpler and +more manageable to insert a second telephone in +the circuit for this purpose. When the box is +inverted on its mouthpiece, and the button <span class="allsmcap">G</span> +ceases to press on the spring <span class="allsmcap">D G</span>, the battery current +reacts on the vibrator of the instrument, and +sends the call to the corresponding station, following +this route: <span class="allsmcap">I D A C B E</span>, line, earth and battery; +and the call goes on until the correspondent +breaks the current by taking up his instrument, +thus warning the other that he is ready to +listen.</p> + +<p><i>System of M. Puluj.</i>—There is yet another call +system, devised by M. Puluj. It consists of two +telephones without mouthpieces, connected together, +and with coils placed opposite the branches<span class="pagenum" id="Page_267">267</span> +of two tuning-forks, tuned as nearly as possible to +the same tone. A small metal bell is fixed between +the opposite faces of the tuning-forks, and a +wire stretched near them is provided with a small +ball in contact with their branches. When the +tuning-fork at the sending station is put in vibration +by striking it with an iron hammer covered with +skin, the tuning fork at the other station vibrates +also, and its ball strikes upon the bell. As soon as +the signal is returned by the second station, mouthpieces +with iron diaphragms are fastened to the telephones, +and the correspondence begins. It seems +that, by the use of a resonator, the sound which +reaches the receiving station may be so intensified +as to become audible in a large hall, and the bell +signal may be heard in an adjoining room, even +through a closed door.</p> + +<p><i>Mr. Alfred Chiddey’s System.</i>—This arrangement +consists of a slender copper tube, eight +inches long, and with an orifice of 1/30 of an inch, +of which the lower end is soldered to the diaphragm +of a telephone. A branch joint, to which an india-rubber +tube is fitted, connects it with a gas jet, +which is lighted and surrounded with a lamp shade, +in such a way as to make it produce, under given +conditions, sounds resembling those of the singing +flames. A perfectly similar system is arranged at +the other end of the line, in such a way that the +sounds emitted in each case shall be precisely in +unison. If the two systems are so regulated as<span class="pagenum" id="Page_268">268</span> +not to emit sounds in their normal condition, they +can be made to sing by causing a tuning-fork in the +vicinity of one or the other to vibrate the same note, +and then the corresponding flame will begin to sing, +producing a vibration in the diaphragm of the +telephone with which it is in correspondence, and +hence will follow the vibration of the diaphragm of +the other telephone, and consequently the vibration +of the flame of the calling instrument. In this way +the call signal may be made without the intervention +of any battery.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="APPLICATIONS_OF_THE_TELEPHONE"><span id="toclink_268"></span>APPLICATIONS OF THE TELEPHONE.</h2> +</div> + +<p>The applications of the telephone are much +more numerous than might be supposed at the first +glance. As far as the telegraphic service is concerned, +its use must evidently be rather limited, +since it cannot register the messages sent, and the +speed of transmission is inferior to that of the +improved system of telegraphs; yet in many cases +it would be very valuable, even for a telegraphic +system, since it is possible to work it without any +special telegraphic training. The first comer may +send and receive with the telephone, and this is +certainly not the case even with the simplest forms +of telegraphic instruments. This system is therefore +already in use in public offices and factories, for communication +in mines, for submarine works, for the +navy, especially when several vessels manœuvre<span class="pagenum" id="Page_269">269</span> +in the same waters, some towed by others; finally, +for military purposes, either to transmit orders to +different corps, or to communicate with schools of +artillery and rifle practice. In America the municipal +telegraphic service and that of telegraphs +limited to the area of towns are conducted in this +way, and it is probable that this system will soon +be adopted in Europe. Indeed, a service of this +kind was established in Germany last autumn at +the telegraph offices of some towns, and the +London Post Office is now thinking of establishing +it in England.</p> + +<p>But, besides its use for the purposes of correspondence, +the telephone can be useful to the telegraphic +service itself by affording one of the +simplest means of obtaining a number of simultaneous +transmissions through the same wire, +and even of being combined in duplex with the +Morse telegraphs. Its applications in the microphonic +form are incalculable, and the proverb which +declares that ‘walls have ears’ may in this way be +literally true. It is alarming to think of the consequences +of such an indiscreet organ. Diplomatists +must certainly redouble their reserve, and tender +confidences will no longer be made with the same +frankness. On this point we cannot think that +much will be gained, but on the other hand the +physician will probably soon make use of this +invention to ascertain more readily the processes +going on within the human body.</p> + +<p><span class="pagenum" id="Page_270">270</span></p> + +<p>APPLICATION OF THE TELEPHONE TO SIMULTANEOUS +TELEGRAPHIC TRANSMISSIONS.</p> + +<p>The simultaneous transmission of several +messages through the same wire is one of the most +curious and important applications of the telephone +to telegraphic instruments which can be made, and +we have seen that it was this application which led +Messrs. Gray and Bell to the invention of speaking +telephones. The admiration which these instruments +have excited has thrown the original idea +into the background, although it has perhaps a +more practical importance. We will now consider +these systems.</p> + +<p>An articulating telephone is not necessary in +order to obtain simultaneous transmission: the +musical telephones devised by MM. Petrina, Gray, +Froment, &c., are quite sufficient, and a brief explanation +of their principle will make this intelligible. +Suppose that there are seven electro-magnetic +vibrators at the two corresponding stations, which +are tuned with the same tuning-fork on the +different notes of the scale, and suppose that a +key-board, resembling the Morse telegraph key, is +arranged so that, by lowering the keys, electric +reaction takes place on each vibrator: it is easy to +see that these vibrators may be made to react in +the same way on the corresponding vibrators of the +opposite station; but they must be tuned on the<span class="pagenum" id="Page_271">271</span> +same note, and the sounds emitted will continue +while the keys are lowered. By keeping them +down for a shorter or longer time, the long or +short sounds which constitute the elements of +telegraphic language in the Morse system may be +obtained, and consequently an audible transmission +becomes possible. Let us now suppose that a +telegraphist accustomed to this mode of transmission +is placed before each of the vibrators, and +that they transmit different messages at the same +moment in this way: the telegraphic wire will be +instantaneously traversed by seven currents, broken +and massed upon each other, and they might be +expected to produce a medley of confused sounds +on the vibrators at the receiving station; but since +they each harmonise with the corresponding vibrator, +they have no sensible influence except on +those for which they are intended. The dominant +sound may be made still more distinct by applying +a Helmholtz resonator to each vibrator,<a id="FNanchor_18" href="#Footnote_18" class="fnanchor">18</a> that +is, an acoustic instrument which will only vibrate +under the influence of the note to which it is tuned.<span class="pagenum" id="Page_272">272</span> +In this way it is possible to select the transmitted +sounds, and only to allow each <i lang="fr">employé</i> to hear +that which is intended for him. Consequently, +however confused the sounds may be on the receiving +vibrators, the person to whom <em>do</em> is assigned will +only receive <em>do</em> sounds, the person to whom <em>sol</em> is +assigned will only receive <em>sol</em> sounds, so that correspondence +may be carried on as well as if they had +each a special wire.</p> + +<p>In the mode we have described, this telegraphic +system only admits of audible transmissions, and +consequently cannot register messages. To supply +this defect, it has been suggested to make the +receiving vibrators react on registers, so arranging +the latter that their electric organ may present such +magnetic inertia, that, when it is influenced by the +vibrations of sound, its effect may be maintained +throughout the time of vibration. Experiments +show that a Morse receiver, worked by the current +of a local battery, will be enough for this purpose; +so that if the musical vibrator is made to react as +a relay, that is, on a contact in connection with the +local battery and the receiver, the dots and dashes +may be obtained on it which are the constituent +elements of the Morse code.</p> + +<p>On these principles, and considering that the<span class="pagenum" id="Page_273">273</span> +musical spaces separating the different notes of the +scale are such as may be easily distinguished by +the resonator, seven simultaneous transmissions +may be obtained on the same wire; but experience +shows that it is necessary to be content with a +much smaller number. Yet this number may +easily be doubled by applying the mode of transmission +in an opposite direction to the system.</p> + +<p>Mr. Bell states that the idea of applying the +telephone to multiple electric transmissions occurred +simultaneously to M. Paul Lacour of Copenhagen, +to Mr. Elisha Gray of Chicago, to Mr. Varley +of London, and to Mr. Edison of New York; but +there is some confusion here, for we have already +seen, from reference to the patents, that Mr. +Varley’s system dates from 1870, that of M. Paul +Lacour from September 1874, that of Mr. Elisha +Gray from February 1875, and those of Messrs. Bell +and Edison were still later. Yet it appears from +Mr. Gray’s specification that he was the first to +conceive and execute instruments of the kind. In +fact, in a specification drawn up on August 6, +1874, he distinctly put forward the system we +have described, and which is the basis of those +of which we have still to speak. This specification +was only an addition to two others made +out in April and June 1874. Mr. Varley’s system +has only an indirect relation to the one we have +described. It appears from what Mr. Bell said on +the subject in a paper addressed to the Society<span class="pagenum" id="Page_274">274</span> +of Telegraphic Engineers in London, that he himself +only attaches a secondary interest to this +invention.</p> + +<p>He said that he had been struck with the idea +that the greater or less duration of a musical sound +might represent the dot and dash of the telegraphic +alphabet, and it occurred to him that simultaneous +telegraphic transmissions, of which the number +should only be limited by the delicacy of the sense +of hearing, might be obtained by suitable combinations +of long and short sounds, and that these +should be effected by a keyboard of tuning-forks +applied to one end of a telegraphic line, and so +arranged as to react electrically on electro-magnetic +instruments striking on the strings of a piano. +For this purpose it would be necessary to assign +an employé to each of the keys for the service of +transmission, and to arrange that his correspondent +should only distinguish his peculiar note among all +those transmitted. It was this idea, Mr. Bell adds, +which led to his researches in telephony.</p> + +<p>For several years he sought for the best mode +of reproducing musical sounds at a distance by +means of vibrating rheotomes: the best results were +given by a steel plate vibrating between two contacts, +of which the vibrations were electrically produced +and maintained by an electro-magnet and a +local battery. In consequence of its vibration, the +two contacts were touched alternately, and the two +circuits were alternately broken; the local circuit<span class="pagenum" id="Page_275">275</span> +which kept the plate in vibration, and the other +which was connected with the line, and reacted on +the distant receiver, so as to effect simultaneous +vibrations in it. A Morse key was placed in the +latter circuit near the sending instrument, and +when it was lowered, vibrations were sent through +the line; when it was raised, these vibrations +ceased, and it is easy to see that, by lowering the +key for a longer or shorter time, the short and long +sounds necessary for the different combinations of +telegraphic language could be obtained. Moreover, +if the vibrating plate of the receiving instrument +were so regulated as to vibrate in unison with the +sending instrument in correspondence, it would +vibrate better with this sender than with another +whose plate was not so adjusted.</p> + +<p>It is evident that different sounds might be +simultaneously transmitted with several plates +by this arrangement of contact breaker, and that +at the receiving station the sounds might be distinguished +by each employé, since the one which +corresponds to the fundamental note of each vibrating +plate is reproduced by that plate. Consequently, +the sounds produced by the vibrating plate of <em>do</em>, +for example, will only be audible at the receiving +station on the plate tuned to <em>do</em>, and the same will +be the case with the other plates; so that the +sounds will reach their destination, if not without +confusion, yet with sufficient clearness to be distinguished +by the employés.</p> + +<p><span class="pagenum" id="Page_276">276</span></p> + +<p>Mr. Bell sums up the defects still existing in +his system as follows:—1st. The receiver of the +messages must have a good musical ear, in order to +distinguish the value of sounds. 2nd. Since the +signals can only take place when the transmitted +currents are in the same direction, two wires must +be employed in order to exchange messages on +each side.</p> + +<p>He surmounted the first difficulty by providing +the receiver with an instrument which he called +the vibrating contact breaker, and which registered +automatically the sounds produced. This contact +breaker was placed in the circuit of a local battery, +which could work a Morse instrument under certain +conditions. When the sounds emitted by the instrument +did not correspond with those for which +it had been tuned, the contact breaker had no +effect on the telegraphic instrument: it only acted +when the sounds were those which were to be interpreted, +and its action necessarily corresponded to +the length of the sounds.</p> + +<p>Mr. Bell adds that he applied the system to +electro-chemical telegraphs; but we need not dwell +on this part of the invention, since, as we have said, +it is no longer his special study.</p> + +<p><i>System of M. Lacour of Copenhagen.</i>—M. +Lacour’s system was patented on the 2nd September, +1874, but his experiments were commenced on +the 5th June of the same year. Since M. Lacour +believed that the vibrations would be imperceptible<span class="pagenum" id="Page_277">277</span> +on long lines, his first attempts were made on a +somewhat short line; but in November 1874 fresh +experiments were made between Fredericia and +Copenhagen on a line 225 miles in length, and it +was ascertained that vibratory effects could be +easily transmitted, even under the influence of a +rather weak battery.</p> + +<figure id="il_59" class="figcenter" style="max-width: 20em;"> + <img src="images/i_p277.jpg" width="765" height="313" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 59.</span> + </figcaption> +</figure> + +<p>In M. Lacour’s system, the sending instrument +is a simple tuning-fork, placed in a horizontal +position, and one of its arms reacts on a contact +breaker, which can produce precisely the same +number of discharges of currents as there are vibrations +of the tuning-fork. If a Morse manipulator +is inserted in the circuit, it is evident that if it is +worked so as to produce the dots and dashes of the +Morse alphabet, the same signals will be reproduced +at the opposite station, and the signals will +be manifested by long and short sounds, if an +electro-magnetic receiver is connected with the +circuit. This sender is shown <a href="#il_59">fig. 59</a>.</p> + +<p><a href="#il_60">Fig. 60</a> represents M. Lacour’s receiver. It +consists of a tuning-fork <span class="allsmcap">F</span> made of soft iron, not of<span class="pagenum" id="Page_278">278</span> +steel like the sending tuning-fork, and each of its +branches is inserted in the bobbin of an electro-magnetic +coil <span class="allsmcap">C C</span>; two distinct electro-magnets <span class="allsmcap">M M</span> +react close to the extremities of the fork, in such a +way that the polarities developed on the two +branches of the fork under the influence of the +coils <span class="allsmcap">C C</span> should be of contrary signs to those of the +electro-magnets <span class="allsmcap">M M</span>.</p> + +<figure id="il_60" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p278.jpg" width="920" height="652" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 60.</span> + </figcaption> +</figure> + +<p>If this double electro-magnetic system is inserted +in a line circuit, it follows that, for each discharge +of the transmitted current, a corresponding +attraction of the branches of the tuning-fork will take +place, and consequently there will be a vibration, +producing a sound, if the discharges are numerous. +This sound will naturally be short or long in proportion +to the duration of the sender’s action, and<span class="pagenum" id="Page_279">279</span> +it will be the same as that of the tuning-fork in that +instrument. Again, if one branch of the tuning-fork +reacts on a contact <span class="allsmcap">P</span> inserted in the circuit of the +local battery communicating with a Morse receiver, +traces will be produced on this receiver of length +varying with the duration of the sounds, for the +Morse electro-magnet will be so quickly affected +by the successive breaks in the current that its +armature will remain stationary throughout each +vibration. ‘I have not yet been able,’ said M. +Lacour in an address delivered before the Danish +Academy of Science in 1875, ‘to calculate the +time necessary for the production of definite vibrations +in the tuning-fork. Different factors have to be +considered, but experiment has shown that the +time which elapses before the local circuit is broken +is such a small fraction of a second as to be almost +inappreciable, even when the current is very weak.</p> + +<p>‘Since intermittent currents only affect a +tuning-fork on condition that it vibrates in unison +with the one which produces them, it follows that +if a series of sending tuning-forks, tuned to the +different notes of the scale, is placed at one end of +a circuit, and if a similar series of electro-magnetic +tuning-forks, in exact accordance with the first, is +placed at the other end of the circuit, the intermittent +currents transmitted by the sending tuning-forks +will be added to each other without becoming +confused, and each of the receiving tuning-forks +will only be affected by the currents emitted by the<span class="pagenum" id="Page_280">280</span> +tuning-fork in unison with it. In this way the combinations +of elementary signals representing a +word may be telegraphed simultaneously.’</p> + +<p>M. Lacour enumerates the ways in which this +system may be applied as follows: ‘If the keys in +connection with the sending tuning-forks are placed +side by side, and are lowered in succession, or two +or three together, it will be enough to play on the +keys as on a musical instrument, in order that the +air may be heard at the receiving station, or the +signals transmitted simultaneously may each belong +to a different message. This system will +therefore allow the furthest station on a line to +communicate with one or several intermediate +stations, and <i lang="la">vice versa</i>, without disturbing the +communication at other stations. In this way two +stations can exchange signals, unperceived by the +rest. The power of sending many signals at once +affords a good means of improving the autographic +telegraph. In the instruments now in use, such as +those of Caselli and D’Arlincourt, there is only +one tracing stylus, and this stylus must pass over the +whole surface of the telegram in order to obtain a +copy of it, but with the telephone a certain number +of styli may be placed side by side in the form +of a comb, and this comb need only be drawn in a +certain direction to pass over the surface of the +telegram. In this way a more faithful copy will +be obtained in a shorter time.’</p> + +<p>M. Lacour also observes that his system<span class="pagenum" id="Page_281">281</span> +possesses a merit already pointed out by Mr. +Varley, namely, that the instruments permit the +passage of ordinary currents without revealing +their presence, whence it follows that the accidental +currents which often disturb telegraphic transmissions +will have no effect on these systems.</p> + +<p>M. Lacour began without applying an electro-magnetic +system to his instrument in order to +maintain the movement of the tuning-fork, but he +soon saw that this accessory was indispensable, +and he made the tuning-forks themselves electro-magnetic. +It also occurred to him to convert the +transmitted currents into pulsatory currents by inserting +an induction coil in the circuit, which was +also done by Mr. Elisha Gray. Finally, in order +to obtain the immediate action of the tuning-forks +and the immediate cessation of their action, he +constructed them so as to reduce their inertia as +much as possible. This was effected by inserting +the two branches of the tuning-fork in the same +coil and by lengthening its handle, and turning +it back so that it might pass through a second +coil, dividing into two branches and embracing +the two vibrating branches, but without touching +them. When a current traverses both coils, it +produces, in the kind of horseshoe magnet formed +by the two systems, opposite polarities which provoke +a double reaction in the vibrating branches—a +reaction by repulsion exerted by the two +branches in virtue of the same polarity, and a<span class="pagenum" id="Page_282">282</span> +reaction by attraction by the other two branches +in virtue of their opposite polarities; and this +double action is repeated by the movements of +a contact breaker applied to one of the vibrating +branches of the tuning-fork.</p> + +<figure id="il_61" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p282.jpg" width="897" height="369" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 61.</span> + </figcaption> +</figure> + +<p><i>Mr. Elisha Gray’s System.</i>—According to the +system originally patented, each sender, represented +<a href="#il_61">fig. 61</a>, consists of an electro-magnet <span class="allsmcap">M M</span> resting +below a small copper tablet <span class="allsmcap">B S</span>, in such a way +that its poles pass through this tablet and are on +a level with its upper surface. A steel plate <span class="allsmcap">A S</span> +is fixed above these poles; its tension can be regulated +by means of a screw <span class="allsmcap">S</span>; and another screw +<i>c</i> is placed on the plate, and is in electric communication +with a local battery <span class="allsmcap">R′</span> by means of a +Morse key. Below the plate <span class="allsmcap">A S</span> there is a contact +<i>d</i> connected with the line wire <span class="allsmcap">L</span>; this contact is +met by the plate at the moment of its attraction +by the electro-magnet, and breaks the current of a +line battery <span class="allsmcap">P</span>, which acts on the receiver of the +opposite station. Finally, the electric communication<span class="pagenum" id="Page_283">283</span> +established between the local battery <span class="allsmcap">R′</span> and +the electro-magnet, as may be seen in the figure, +produces vibrations in the steel plate <span class="allsmcap">A S</span> at each +lowering of the key, as in the case of ordinary vibrations—vibrations +which, with a suitable tension of +the plate and a given intensity of the battery <span class="allsmcap">R′</span>, can +produce a definite musical note. Moreover, since +at each vibration the plate <span class="allsmcap">A S</span> meets the contact, +discharges of the line current take place through +the line <span class="allsmcap">L</span>, and react on the receiving instrument, +causing it to reproduce exactly the same vibrations +as those of the sending instrument.</p> + +<figure id="il_62" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p283.jpg" width="883" height="363" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 62.</span> + </figcaption> +</figure> + +<p>The receiving instrument represented <a href="#il_62">fig. 62</a> +exactly resembles the one we have just described, +except that there is no contact <i>d</i> below the vibrating +plate <span class="allsmcap">A S</span>, and the contact <i>c</i>, instead of communicating +with the line wire, is in electric connection +with a register <span class="allsmcap">E</span> and a local battery <span class="allsmcap">P</span>. It +follows from this arrangement that when the plate +<span class="allsmcap">A S</span> vibrates under the influence of the broken<span class="pagenum" id="Page_284">284</span> +currents passing through the electro-magnet <span class="allsmcap">M M</span>, +similar vibrations are sent through the register; +but if the electro-magnetic organ of this register +is properly regulated, these vibrations can only +produce the effect of a continuous current, and hence +the length of the traces left on the instrument will +vary with the duration of the sounds produced. +In this way the registration of the dashes and dots +which constitute the signs of the Morse vocabulary +will be effected.</p> + +<p>If it is remembered that the plate <span class="allsmcap">A S</span> vibrates +under the influence of electro-magnetic attractions +more readily in proportion to their approximation +in number to the vibrations corresponding to +the fundamental sound it can emit, it becomes clear +that if this plate is tuned to the same note as that of +the corresponding instrument, it will be rendered +peculiarly sensitive to the vibrations transmitted by +the sender, and the other vibrations which may +affect it will only act faintly. Moreover, a resonator +placed above the plate will greatly increase this +predisposition; so that if several systems of this +kind, tuned to different notes, produce simultaneous +transmissions, the sounds corresponding to +the different vibrations will be in a certain sense +selected and distributed, in spite of their combination, +into the receivers for which they are specially +adapted, and each of them may retain the traces +of the sounds emitted by adding the register, which +may be so arranged as to act as an ordinary Morse<span class="pagenum" id="Page_285">285</span> +receiver. Mr. Gray states that the number of +sending instruments and independent local circuits +may be equal to that of the tones and semitones +of two or more octaves, provided that each vibrating +plate be tuned to a different note of the scale. +The instruments may be placed side by side, and +their respective local keys, arranged like the keys +of a piano, will make it easy to play an air combining +notes and chords; there may also be an +interval between the instruments, which may be +sufficiently far from each other to allow the employés +to work without being distracted by sounds +not intended for them.</p> + +<p>In a new arrangement, exhibited at the Paris +Exhibition, 1878, Mr. Gray considerably modified +the way of working the various electro-magnetic +organs which we have just described. In this case, +the plates consist of tuning-forks with one branch +kept in continual vibration at both stations, and +the signals only become perceptible by intensifying +the sounds produced. This arrangement follows +from the necessity of keeping the line circuit always +closed for multiple transmissions of this nature, so +as to react with pulsatory currents, which are alone +able, as we have already seen, to retain the individual +character of several sounds simultaneously +transmitted.</p> + +<figure id="il_63" class="figcenter" style="max-width: 18em;"> + <img src="images/i_p286.jpg" width="719" height="880" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 63.</span> + </figcaption> +</figure> + +<p>Under these conditions, the sender consists, +as we see (<a href="#il_63">fig. 63</a>), of a bar tuning-fork, <i>a</i>, which +is grooved for the passage of a runner, heavy<span class="pagenum" id="Page_286">286</span> +enough to tune the fork to the desired note, and it +oscillates between two electro-magnets <i>e</i> and <i>f</i> and +two contacts <span class="allsmcap">I</span> and <span class="allsmcap">G</span>. The difference of resistance +in the electro-magnets is very great: in the one <i>f</i> +the resistance is equal to 2¾ miles of telegraphic wire, +in the other it does not exceed 440 yards. When +electric communication is established as we see in +the figure, the following effect takes place. Since the +current of the local battery through the two electro-magnets +is broken by the rest-contact of the Morse +key <span class="allsmcap">H</span>, the plate <i>a</i> is subject to two contrary<span class="pagenum" id="Page_287">287</span> +actions; but since the electro-magnet <i>f</i> has more +turns than the electro-magnet <i>e</i>, its action is preponderant, +and the plate is attracted towards <i>f</i>, and +produces a contact with the spring <span class="allsmcap">G</span>, which opens +a way of less resistance for the current. Since the +current then passes almost wholly through <span class="allsmcap">G</span>, <i>b</i>, 1, +2, <span class="allsmcap">B</span>, the electro-magnet is now able to act; the +plate <i>a</i> is then attracted towards <i>e</i>, and, by producing +a contact on the spring <span class="allsmcap">I</span>, it sends the current +of the line <span class="allsmcap">B P</span> through the telegraphic line, if the +key <span class="allsmcap">H</span> is at the same time lowered on the sending +contact: if not, there will be no effect in this direction, +but since the plate <i>a</i> has left the spring <span class="allsmcap">G</span>, the +first effect of attraction by the electro-magnet <i>f</i> +will be repeated, and this tends to draw the plate +again towards <i>f</i>. This state of things is repeated +indefinitely so as to maintain the vibration of the +plate, and to send out signals corresponding with +these vibrations whenever the key <span class="allsmcap">H</span> is lowered. +The elastic nature of the plate makes these vibrations +more easy, and it ought also to be put in +mechanical vibration at the outset.</p> + +<p>The receiver, represented <a href="#il_64">fig. 64</a>, consists of an +electro-magnet <span class="allsmcap">M</span>, mounted on a sounding-box <span class="allsmcap">C</span>, +and having an armature formed by a tuning-fork +<span class="allsmcap">L L</span> firmly buttressed on the box by a cross bar <span class="allsmcap">T</span>. +There is a runner <span class="allsmcap">P</span> on the armature, sliding in a +groove, which makes it possible to tune the vibrations +of the tuning-fork to the fundamental note of +the sounding-box <span class="allsmcap">C</span>, which is so arranged as to<span class="pagenum" id="Page_288">288</span> +vibrate in unison with it. Under these conditions, +the box as well as the tuning-fork will act as an +analyser of the vibrations transmitted by the currents, +and may set the register at work by itself +reacting on a breaker of the local current. To +obtain this result, a membrane of gold-beater’s +skin or parchment must be stretched before the +opening of the box, and a platinum contact must be +applied to it, so arranged as to meet a metallic +spring connected with any kind of register or a +Morse instrument, when the membrane vibrates. As, +however, in America the messages are generally +received by sound, this addition to the system is +not in use.</p> + +<figure id="il_64" class="figcenter" style="max-width: 23em;"> + <img src="images/i_p288.jpg" width="907" height="728" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 64.</span> + </figcaption> +</figure> + +<p><span class="pagenum" id="Page_289">289</span></p> + +<p>The instrument is not only regulated by the +runner <span class="allsmcap">P</span>, but also by a regulating screw <span class="allsmcap">V</span> which +allows the electro-magnet <span class="allsmcap">M</span> to be properly +adjusted. The regulating system is made more +exact by the small screw <span class="allsmcap">V</span>, and the instrument is +connected with the line by the binding screw <span class="allsmcap">B</span>. +Of course this double arrangement is necessary for +each of the sending systems.</p> + +<p>As I have already said, seven different messages +might theoretically be sent at once in this way, +but Mr. Gray has only adapted his instrument for +four; he has, however, made use of the duplex +system, which allows him to double the number of +transmissions, so that eight messages may be sent +at the same time, four in one direction, and four in +another.</p> + +<p>Mr. Hoskins asserts that this system has been +worked with complete success on the lines of the +Western Union Telegraph Company, from Boston +to New York, and from Chicago to Milwaukee. +Since these experiments were made, fresh improvements +have rendered it possible to send a much +larger number of messages.</p> + +<p>Mr. Gray has also, aided by Mr. Hoskins, +devised a system by which telephonic messages +may be sent on a wire previously used for Morse +instruments. Mr. Varley had already solved this +problem, but Mr. Gray’s system seems to have +produced important results, and has therefore a +claim to our attention. We do not, however, describe<span class="pagenum" id="Page_290">290</span> +it here, since it is not within the lines marked out +for us, and those who are interested in the subject +will find all the necessary details in a paper inserted +in the ‘Journal of the Society of Telegraphic Engineers, +London,’ vol. vi.</p> + +<p><i>Mr. Varley’s System.</i>—This system is evidently +the earliest in date, since it was patented in 1870, +and the patent describes the principle of most of the +arrangements which have since been adopted by +Messrs. Lacour, Gray, and Bell. It is based upon +the use of his own musical telephone, which we +have already described, but with some variations +in its arrangement, which make it somewhat like +the Reiss system.</p> + +<p>It was Mr. Varley’s aim to make his telephone +work in conjunction with instruments with ordinary +currents, by the addition of rapid electric waves, +incapable of making any practical change in the +mechanical or chemical capacity of the currents +which serve for the ordinary signals, yet able to +make distinct signals, perceptible to the ear and +even to the eye. He says: ‘An electro-magnet +offers at first a great resistance to the passage of +an electric current, and may consequently be regarded +as a partially opaque body with respect to +the transmission of very rapid inverse currents or +of electric waves. Therefore, if a tuning-fork, or an +instrument with a vibrating plate, tuned to a given +note, be placed at the sending station, and so +arranged as to be kept in constant vibration by<span class="pagenum" id="Page_291">291</span> +magnetic influence, the current which acts upon it +must be passed into two helices placed one above +the other so as to constitute the primary helix of +an induction coil: in this way it will be possible to +obtain in two distinct circuits two series of rapidly +broken currents, which will correspond to the two +directions of the vibrations of the tuning-fork, +and we shall also have the induced currents produced +in the secondary helix by these currents, +which may act on a third circuit. This third +circuit may be placed in connection with a telegraphic +line previously used by an ordinary telegraphic +system, if a condenser is applied to it, and +in this way two different transmissions may be +obtained simultaneously.’</p> + +<figure id="il_65" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p291.jpg" width="823" height="311" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 65.</span> + </figcaption> +</figure> + +<p><a href="#il_65">Fig. 65</a> represents the arrangement of this +system. <span class="allsmcap">D</span> is the vibrating plate of the tuning-fork +designed to produce the electric contacts necessary +to maintain it in motion. These contacts are at <span class="allsmcap">S</span> +and <span class="allsmcap">S′</span>, and the electro-magnets which affect it are +at <span class="allsmcap">M</span> and <span class="allsmcap">M′</span>. The induction coil is at <span class="allsmcap">I′</span>, and the +three helices of which it is composed are indicated<span class="pagenum" id="Page_292">292</span> +by the circular lines which surround it. There is a +Morse manipulator at <span class="allsmcap">A</span>, another at <span class="allsmcap">A′</span>, and the +two batteries which work the system are at <span class="allsmcap">P</span> and +<span class="allsmcap">P′</span>. The condenser is at <span class="allsmcap">C</span>, and the telephone is at +the end of the line <span class="allsmcap">L</span>.</p> + +<p>When the vibration of the plate <span class="allsmcap">D</span> tends to the +right, and the electric contact takes place at <span class="allsmcap">S′</span>, +the current of the battery <span class="allsmcap">P′</span>, after traversing the +primary helix, reaches the electro-magnets <span class="allsmcap">M M′</span>, +which give it an impulse in the contrary direction. +When, on the other hand, it tends to the left, the +current is sent through the second primary circuit, +which will be balanced by the first. Consequently +there will be a series of reversed currents in the induced +circuit corresponding to the key <span class="allsmcap">A′</span>, which will +alternately charge and discharge the condenser <span class="allsmcap">C</span>, +thus sending into the line a corresponding series of +electric undulations which will react on the telephone +placed at the end of the line; and as the +duration of the transmitted currents will vary with +the time that the key <span class="allsmcap">A′</span> is lowered, a correspondence +in the Morse code may be obtained +in the telephone, while another correspondence is +exchanged with the key <span class="allsmcap">A</span> and the ordinary Morse +receivers.</p> + +<p>In order to render the vibratory signals visible, +Mr. Varley proposes to use a fine steel wire, +stretched through a helix and facing a narrow slit, +to reproduce the vibrations. A light, which is +intercepted by the wire, is placed behind the slit.<span class="pagenum" id="Page_293">293</span> +As soon as a current passes, the wire vibrates and +the light appears. A lens is placed so as to +magnify the image of the luminous slit, and project +it on a white screen while the wire is in vibration.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="VARIOUS_USES_OF_THE_TELEPHONE"><span id="toclink_293"></span>VARIOUS USES OF THE TELEPHONE.</h2> +</div> + +<p><i>Its domestic application.</i>—We have seen that +telephones may be used with advantage in public +and private offices: they can be set up at a much +less expense than acoustic tubes, and in cases +where the latter would never be employed. With +the aid of the calls we have described, they offer +the same advantages, and the connection between +the instruments is more easily concealed. The +difference of price in establishing them is in the +ratio of one to seven.</p> + +<p>For this purpose electro-magnetic telephones +are evidently the best, since they require no battery +and are always ready to work. They are already +in use in many Government offices, and it is probable +that they will soon be combined with electric +bells for the service of hotels and of large public +and private establishments: they may even be +used in private houses for giving orders to servants +and porters, who may thus save visitors from the +fatigue of a useless ascent of several storeys.</p> + +<p>In factories, telephones will certainly soon replace +the telegraphic communication which has already +become general. They may not only be used +for ordinary messages, but to call for help in case of<span class="pagenum" id="Page_294">294</span> +fire, and they will become an integral part of several +systems already established for this purpose.</p> + +<p>In countries which have free telegraphic communication, +the telephone has already replaced in +great measure the private telegraph instruments +which have hitherto been in use; and if the same +privilege is extended to France, no other mode of +correspondence will be used.</p> + +<p><i>Its application to telegraphic service.</i>—The +advantage to be derived by the telegraphic service +from the telephone is rather limited, since, as far as +the speed of transmission is concerned, it is of less +value than many of the telegraphic instruments +now in use, and the messages which it produces +cannot be registered. Yet in municipal offices not +overburdened with messages they offer the advantage +of not requiring a trained service. On longer +lines their use would be of little value. The ‘Berne +Telegraphic Journal’ has published some interesting +remarks on this subject, of which the following is a +summary.</p> + +<p>1st. In order to send a message with the special +advantages of the system, the sender ought to be +able to address his correspondent without the intervention +of an official. Those who are acquainted +with the network of wires know this to be impossible. +Intermediate offices for receiving messages +are essential, and the public cannot be admitted to +those set apart for sending and receiving; consequently +the sender must deliver a written message.</p> + +<p><span class="pagenum" id="Page_295">295</span></p> + +<p>2nd. If the message is written, the chief advantage +of the instrument is lost, since it must +be read and uttered aloud, which could not be +done if expressed in a language with which the +employés were unacquainted.</p> + +<p>3rd. The instruments now in use at the telegraph +offices can transmit messages more quickly +than if they were spoken.</p> + +<p>In Germany, however, a telephone service has +been established in several telegraph offices, and its +possible advantages are enumerated as follows in +the official circular which created it:</p> + +<p>‘The offices which will be opened to the public +for the service of telephonic messages in Germany +will be regarded as independent establishments; +yet they will be in connection with the ordinary +telegraph offices, which will undertake to send +telephonic messages through their wires.</p> + +<p>‘The transmission will take place as follows: +The sending office will request the receiving office +to prepare the instrument; as soon as the tubes +are adjusted, the sending office will give the signal +for despatching the verbal message.</p> + +<p>‘The sender must speak slowly and clearly, +without raising his voice; each syllable must be +distinctly pronounced; the final syllables especially +must be well articulated, and there must be a pause +after each word, in order to give the receiver time +to write it down.</p> + +<p>‘When the telegram has been received, the<span class="pagenum" id="Page_296">296</span> +employé at the receiving office must verify the +number of words; then he must repeat through the +telephone the whole message without pausing, so +as to make sure that there is no mistake.</p> + +<p>‘In order to ensure secrecy, the telephones are +placed apart, where persons unconnected with the +service cannot hear the verbal message, and the +employés are forbidden to reveal to anyone the +names of the correspondents.</p> + +<p>‘The charge for telephonic messages, as for the +ordinary telegraphic services, is at the rate of so +much a word.’</p> + +<p>The use of the telephone has also been suggested +for verifying the perfect junction of telegraphic +wires. It is certain that, if the junction is complete, +no abnormal sounds will be heard, or only those +which result from accidental currents; but if the +junction is bad, the imperfect contacts which take +place produce variations in electric intensity which +are translated into the more or less marked sounds +observed in the telephone.</p> + +<p>M. Mauborgne, the electrician attached to the +Northern Railway of France, has lately used the +telephone instead of the galvanometer to ascertain +the condition of the circuits in correspondence with +the instruments in use for electric signals. The +reactions produced on the galvanometer needle by +the pieces of iron which are placed at the sides of +the railway often make its indications uncertain, +and a strong wind produces irregular movements<span class="pagenum" id="Page_297">297</span> +in the instrument which interfere with observations. +It was also necessary to place the galvanometer +with due regard to the points of the compass, +and to wait for the needle to settle, which +involved loss of time. The operation is easily +accomplished with the telephone, since the strokes +of the call-bell are distinctly reproduced; it is +made to ring by working the contacts which need +verification, and in the same way the condition of +the battery can be ascertained.</p> + +<p><i>Application to military purposes.</i>—Since the +telephone was invented, numerous experiments +have been made in different countries to ascertain +whether it would be of use in military operations. +These experiments have hitherto been only +moderately satisfactory, on account of the noise +inseparable from an army, which generally makes it +impossible to hear the telephone, and every means +of intensifying its sounds has been eagerly sought. +It was at first supposed that the discovery of +the microphone had solved the problem, and I +received many enquiries from military schools on +the subject, but I have not been able to see that +anything has been gained from this point of view. +The telephone is, however, of great use in schools of +artillery and rifle practice. Now that firearms carry +so far, it has become necessary to be informed by +telegraph of the points hit on the target, in order to +judge of the accuracy of aim, and for this purpose +telegraphic targets were suggested; but telephones<span class="pagenum" id="Page_298">298</span> +are much to be preferred, and they are now used +with good effect.</p> + +<p>If the telephone is unsuited for the service of +the flying telegraph in the field, it may be of great +use in the defence of towns, to transmit the orders +of the commandant to different batteries, and even +for the exchange of correspondence with captive +balloons sent to hover over fields of battle.</p> + +<p>In spite of the difficulties attending its use, the +experiment was made by the Russians in the late +war: the cable wire of communication was 500 or +600 yards long, and so light that it could be laid +by one man. The ‘Telegraphic Journal’ of March +15, 1878, states that the bad weather did not +interfere with the working of the instruments; but +the noise made it difficult to hear, and it was +necessary to cover the head with a hood to intercept +external sounds. This cannot be considered +a satisfactory result, yet the telephone may be of +great service to an army by intercepting the +enemy’s messages: a bold man, provided with a +pocket telephone, who placed himself in a retired +spot, might divert the current of the enemy’s +telegraphic wire into his telephone, and get possession +of all his despatches, as we saw was the case +at Clermont. He might even do this by diverting +the current to earth or to a rail of the railway line. +These are suggestions for future research, and it is +probable that they may some day be turned to +practical account.</p> + +<p><span class="pagenum" id="Page_299">299</span></p> + +<p><i>Its application to the navy.</i>—The telephone may +be of the greatest use in naval matters, for the +service of electro-semaphores, for island forts and +ships at anchor. M. Pollard says that ‘experiments +made between the Préfecture Maritime at +Cherbourg, the semaphores and the forts on the +mole, demonstrate the advantage there would be in +establishing telephones at these stations, since they +would ensure an easy communication between the +vessels of a squadron and the land they are +approaching. By sinking small cables which come +to the surface of the water along mooring chains, +and terminate in buoys or cases which remain +permanently in the harbour, the ships of war may +in this way place themselves in communication with +the Préfecture Maritime as they cast anchor, and, +by temporarily connecting the vessels together +with light cables, the admiral may communicate +freely with the whole squadron.’</p> + +<p>The telephone has been tried on board ship for +transmitting orders, but without success, on account +of the noise always going on in a vessel.</p> + +<p>The telephone may be usefully applied to the +service of submarine torpedoes. We have already +seen how it may be applied in connection with the +microphone, but it may also be used in firing the +torpedoes after the exact position of the enemy’s +ship has been ascertained from two reconnaissances +taken from different parts of the coast.</p> + +<p>The telephone, again, makes it possible to<span class="pagenum" id="Page_300">300</span> +verify the condition of torpedoes, and to ascertain +if there is any fault in the circuit within the explosives. +For this purpose a very weak current +has been used, and a galvanometer is not always +able to indicate the fault, while the extreme sensitiveness +of the telephone will do so in the simplest +way.</p> + +<p>Captain M’Evoy, of the American Army, suggested +a way of ascertaining, while on shore, the +condition of torpedoes under water, by connecting +the buoys which support them with the land by +means of a telephonic line. By inserting, in the +buoy which supports the torpedo, metallic disks, +so arranged as to vibrate with every movement +caused by the waves upon the buoy, a continuous +noise will be heard in the telephone, after the +circuit has been completed by the metallic disks; +and the noise will go on as long as the disks +continue to oscillate, and will cease as soon as the +buoy is completely covered by the water. When +it ceases, therefore, if not affected by some accidental +cause, it may be supposed that the +enemy’s ship is passing over the buoy.</p> + +<p>M. Trève, again, has shown that the telephone +might be used with advantage for the telegraphic +communication between vessels in tow, and +M. des Portes has applied it with good effect to +diving operations. In this instance, one of the +glass panes in the helmet is replaced by a copper +plate in which the telephone is framed, so that the<span class="pagenum" id="Page_301">301</span> +diver need only make a slight movement of his +head in order to receive or address communications +to those in charge of the apparatus. With this +system the keels of vessels may be examined, and +an account given of their condition, without bringing +up the divers, which has hitherto been necessary.</p> + +<p>M. de Parville, the able and learned editor +of the <i lang="fr">Journal Scientifique</i> and the science department +of the <i lang="fr">Journal des Débats</i>, has suggested a +new and interesting application of the telephone. +It concerns the possibility of making use of it to +determine the precise position of the magnetic +meridian, that is, the true direction of the magnetised +needle.</p> + +<p>For this purpose a Bell telephone is necessary, +of which the magnetic core is formed of an iron +rod a mètre in length, kept, by a suitable suspension, +at nearly the same angle of inclination as a +dipping-needle. This rod will be magnetised under +the influence of terrestrial magnetism, and the +telephone will be able to transmit the sounds produced +by some sort of vibrator placed near its +mouthpiece. These sounds will be strong in proportion +to the degree of magnetisation of the bar; +and if the telephone is turned round the horizon, +keeping the bar at the same angle of inclination, the +sounds transmitted to the receiving telephone will +be greatest when the axis of the bar is in the plane +of the magnetic meridian, and least when it is at +90°. It will therefore be possible to ascertain from<span class="pagenum" id="Page_302">302</span> +the direction of the axis at the moment when +the sounds are no longer heard, the exact inclination +of the magnetic needle from north to south, for +it will be given by the perpendicular to the line +which is followed by the axis of the iron bar at +that moment.</p> + +<p>It is possible that, with this system, the disturbing +influence on the magnetic needle of the mass of +iron in iron-plated vessels might be almost destroyed, +and a more exact orientation than that of +the compass might be obtained. The same process +may make it possible to estimate and measure the +variations of terrestrial magnetism. M. de Parville +has not himself tried to apply this system; but Mr. +Blake’s experiments, of which we spoke in an early +part of this work, make it probable that it might +be done with advantage.</p> + +<p><i>Application to industry.</i>—One of the earliest +and most important applications of the telephone +is that which was first made to the service of +mines in England and America in the autumn +of 1877. The great length of the galleries is +well known, and had already involved the use of +the electric telegraph for transmitting orders; but +the miners did not understand how to work these +instruments, and the service was ill performed. +Thanks to the telephone, through which the first +corner can send and receive a message, there is no +longer any difficulty in the communication between +the galleries and the surface of the mine.</p> + +<p><span class="pagenum" id="Page_303">303</span></p> + +<p>The ventilation of mines can also be regulated +by the aid of telephones. If one of these instruments +is placed near a wheel kept in motion by +the air which passes through the ventilating shaft, +and another is placed in the inspector’s office he +can ascertain by the sound if the ventilation is duly +carried on, and if the machine works regularly.</p> + +<p><i>Application to scientific research.</i>—M. d’Arsonval’s +experiments, which we have already mentioned, +show that the telephone can be used as an extremely +sensitive galvanoscope; but since it can +only produce sounds under the influence of broken +currents, the circuit on which the experiment is +made must be divided at rather close intervals. It +has been seen that it is not even necessary to insert +the telephone in the circuit: it may be influenced, +when at a distance, either immediately or by the +induction of the broken current on a circuit placed +parallel to the first, and the force of these effects +may be increased by the reaction of a core of +iron, round which the inducing circuit is wound. +The drawback to this system is that the direction +of the current is not ascertained, so that it cannot +be used as a measuring instrument; but, on the +other hand, it is so sensitive, so easy to arrange, +and so inexpensive, that it might be of the greatest +use as a galvanoscope.</p> + +<p>Mr. Warren de La Rue has also made use of the +telephone in his researches into the electric discharges +of high-tension batteries, in order to<span class="pagenum" id="Page_304">304</span> +follow the different phases of the discharge during +the luminous phenomena which it produces. In +this way he ascertained that when a condenser is +placed in connection with a battery formed of a +considerable number of insulated elements, and is +gradually discharged through a Geissler tube, a +dull and faint sound is heard in the telephone, as +long as the stratifications of light appear to be +perfectly stable; but the sound becomes considerably +stronger, and sometimes even piercing, +in proportion to the diffusion of these stratifications, +and to their approach to the point of +extinction: whence it is shown that the discharge +of a battery into tubes in which a vacuum has been +made is intermittent.</p> + +<p>Mr. Spottiswoode has repeated the same experiments +with the discharges of Holtz machines, +and with large condensers, and he found that the +most piercing sounds produced by the telephone +coincided with the greatest development of the +stratifications. These sounds, however, sometimes +ceased for a moment. It was even possible to +ascertain, from the intensity of the sounds produced, +the differences of tension which might be +manifested in the charge of the condenser and +the slackening of the machine’s motion, and the +differences of intensity in these sounds might in +some cases exceed an octave. The fall in the +scale generally appeared in half-tones instead of +gradually, and the introduction of resistances into<span class="pagenum" id="Page_305">305</span> +the circuit modified the sounds very much: they +might even be intensified by approaching the +finger to the discharging tube.</p> + +<p>From experiments made with the telephone +between Calais and Boulogne, it appears that this +instrument might be applied with advantage to the +science of projectiles. In fact, in some artillery +practice which took place on the shore at Boulogne, +a telephone was placed close to the gun, and the +explosion was heard at a distance of nearly two +miles, where the projectile fell. It was possible to +estimate its velocity by measuring the lapse of +time between the moment when the projectile left +the gun, and its fall. This calculation is usually +made by observing the flash from the cannon’s +mouth; but in some cases, as in a fog or in practice +at long ranges, the telephone may be usefully +substituted for ocular observation. On the field +of battle, an observer, provided with a telephone +and placed on a hill, might rectify from a distance +the aim of his battery, which is generally established +in a sheltered and less elevated place.</p> +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_307">307</span></p> + +<h2 class="nobreak" id="THE_PHONOGRAPH"><span id="toclink_307"></span>THE PHONOGRAPH.</h2> +</div> + +<p>Mr. Edison’s Phonograph, which has for the last +year attracted so much attention, is an instrument +which not only registers the different vibrations +produced by speech on a vibrating plate, but reproduces +the same words in correspondence with the +traces registered. The first function of this instrument +is not the result of a new discovery. Physicists +have long sought to solve the problem of registering +speech, and in 1856 Mr. Leo Scott invented an +instrument well known to physicists under the +name of Phonautograph, which completely solved the +difficulty: this instrument is described in all the +more detailed treatises on physics. But the second +function of the Edison instrument was not realised +nor even mentioned by Mr. Scott, and we are surprised +that this able inventor should have regarded +Mr. Edison’s invention as an injurious act of spoliation. +We regret on his own account, since no +one has wished to deprive him of the credit he +deserves, that he should have published a pamphlet +on the subject, couched in terms of such asperity,<span class="pagenum" id="Page_308">308</span> +which proves nothing, and only states facts which +were well known to all physicists. If any other +person could claim the invention of the phonograph, +at least in its most curious property of reproducing +speech, it would certainly be M. Charles Cros; for +in a sealed paper deposited at the Académie des +Sciences, April 30, 1877, he pointed out the +principle of an instrument by means of which +speech might be reproduced in accordance with +the marks traced on a register like that of the +phonautograph.<a id="FNanchor_19" href="#Footnote_19" class="fnanchor">19</a> Mr. Edison’s patent, in which the<span class="pagenum" id="Page_309">309</span> +principle of the phonograph is first indicated, is +dated July 31, 1877, and he was still only +occupied with the repetition of the Morse signals. +In this patent Mr. Edison described a mode of +registering these signals by means of indentations +traced with a stylus on a sheet of paper wound +round a cylinder, and this cylinder had a spiral +groove cut on its surface. The tracings thus +produced were to be used for the automatic transmission +of the same message, by passing it again +under a stylus which should react on a current +breaker. In this patent, therefore, nothing is said<span class="pagenum" id="Page_310">310</span> +of the registration of speech or of its reproduction; +but, as the ‘Telegraphic Journal’ of May 1, 1878, +observes, the foregoing invention gave him the +means of solving this double problem as soon as +it was suggested to him. If we may believe the +American journals, this suggestion soon came, and +it was the result of an accident.</p> + +<p>In the course of some experiments Mr. Edison +was making with the telephone, a stylus attached +to the diaphragm pierced his finger at the moment +when the diaphragm began to vibrate under the +influence of the voice, and the prick was enough to +draw blood. It then occurred to him that if the +vibrations of the diaphragm enabled the stylus +to pierce the skin, they might produce on a flexible +surface such distinct outlines as to represent all the +undulations produced by the voice, and even that +the same outlines might mechanically reproduce the +vibrations which had caused them, by reacting on +a plate capable of vibrating in the same way as +that which he had already used for the reproduction +of the Morse signals. From that moment the +phonograph was discovered, since there was only a +step between the idea and its realisation, and in +less than two days the instrument was made and +tried.</p> + +<p>This is an ingenious story, yet we would rather +believe that the discovery was made in a more +serious spirit. In fact, such an inventor as Mr. +Edison, who had discovered the electro-motograph,<span class="pagenum" id="Page_311">311</span> +and had applied it to the telephone, was already +on the way to discover the phonograph, and we +think too well of his powers to attach much credit +to this American romance. Besides, Mr. Edison +was well acquainted with Mr. Scott’s phonautograph.</p> + +<p>Mr. Edison’s phonograph was only patented in +January 1877. Consequently, when we look at the +principle of the invention, M. Cros undoubtedly +may claim priority; but it is a question whether the +system described in his sealed paper, and published +in the <i lang="fr">Semaine du Clergé</i>, October 8, 1877, would +have been capable of reproducing speech. Our +doubt seems justified by the unsuccessful attempts +of the Abbé Leblanc to carry out M. Cros’ idea. +When we have to do with such undulating and +complex vibrations as those involved in the reproduction +of articulate words, it is necessary that +the stereotyping should in some sense be effected +by the words themselves, and their artificial reproduction +will necessarily fail to mark the slight differences +which distinguish the delicate combinations +of speech. Besides, the movements performed by +a point confined to a groove that follows a sinusoidal +curve cannot be effected with all the freedom +necessary for the development of sounds, and the +friction exerted on the two edges of the groove +will often be of a nature to stifle them. A distinguished +member of the Société de Physique, when +I exhibited the phonograph to that society, justly<span class="pagenum" id="Page_312">312</span> +said that Mr. Edison’s whole invention consisted in +the thin metallic sheet on which the vibrations are +inscribed; this sheet permits the movements of the +vibrating plate to be directly stereotyped, and +thereby the problem is solved. It was necessary to +find such an expedient, and it was done by Mr. +Edison, who is therefore the inventor of the phonograph.</p> + +<p>After M. Cros, and before Mr. Edison, MM. +Napoli and Marcel Deprez attempted to make a +phonograph, but with so little success that they +believed at one time the problem to be insoluble, +and threw doubts on Mr. Edison’s invention +when it was announced to the Société de Physique. +They subsequently resumed their labours, and lead +us to hope that they may eventually produce a +phonograph of more perfect construction than that +of Mr. Edison. We shall have more to say on this +subject.</p> + +<p>In conclusion, the mechanical reproduction of +speech was first effected by Mr. Edison, and in so +doing he has accomplished one of the most curious +and important discoveries of our time, since it has +shown that this reproduction was much less complicated +than had been supposed. Yet the theoretical +consequences of the discovery must not be +exaggerated, since I do not consider it by any +means proved that our theories on the voice are +incorrect. There is in fact a great difference +between the reproduction of a sound which has<span class="pagenum" id="Page_313">313</span> +been uttered, and the mode in which the same +sound was produced. The reproduction may be +easily effected, as M. Bourseul has remarked, as +soon as a mode has been discovered of transmitting +the vibrations of air, however complex they +may be; but in order to produce the complex +vibrations of speech by the voice, several special +organs must be exercised—first, the muscles of the +throat; secondly, the tongue, the lips, and even the +teeth—and for this reason an articulating machine +is necessarily very complex.</p> + +<p>Surprise was expressed that the speaking +machine, which was brought from America two +years ago, and exhibited at the Grand Hôtel, Paris, +was so extremely complicated, since the phonograph +solved the problem in such a simple way. +This is because the latter instrument only reproduces +speech, while the former utters it, and the +inventor of the speaking machine had to employ +in his mechanism all the organs which are +necessary in our organism for the reproduction of +speech. The problem was infinitely more complex, +and this invention has not attracted all the attention +it deserved. We shall speak of it presently. +We must now describe the phonograph and the +different applications which have been, or which +may be, made of it.</p> + +<p><i>Description of Phonograph, and mode of using +it.</i>—The first and best known model of this instrument, +which we represent in <a href="#il_66">fig. 66</a>, simply consists<span class="pagenum" id="Page_314">314</span> +of a registering cylinder <span class="allsmcap">R</span>, set in motion with the +hand by a winch <span class="allsmcap">M</span>, before which a vibrating plate +is placed, furnished on its face with a telephone +mouthpiece <span class="allsmcap">E</span>, and on the reverse side with a tracing +point. This tracing point, which is seen at <i>s</i> +in the section of the instrument given in <a href="#il_68">fig. 68</a>, is +not fixed directly on the plate; it rests on a spring +<i>r</i>, and a caoutchouc pad <i>c</i> is placed between it and +the vibrating disk. This pad is formed of the end +of a tube which is designed to send the vibrations +of the plate to the point <i>s</i> without stifling them. +Another pad <i>a</i>, placed between the plate <span class="allsmcap">L L</span> and +the rigid support of the point, moderates in some +degree these vibrations, which, without this precaution, +would generally be too powerful.</p> + +<figure id="il_66" class="figcenter" style="max-width: 28em;"> + <img src="images/i_p314.jpg" width="1088" height="676" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 66.</span> + </figcaption> +</figure> + +<p><span class="pagenum" id="Page_315">315</span></p> + +<p>The cylinder, of which the axis <span class="allsmcap">A A</span> (<a href="#il_66">fig. 66</a>) is +cut at one end like a screw, to enable it to make +a lateral progressive movement simultaneously +with the rotatory movement effected on itself, has +on its surface a narrow screw-thread coinciding +with that of the axis, and when the tracing point is +inserted, it is able to pass along it for a distance +corresponding to the time occupied in turning the +cylinder. A sheet of tinfoil or of very thin copper +is carefully applied to the surface of the cylinder, +and it should be slightly pressed down upon it, +so as to show a faint tracing of the groove, and +to allow the point of the vibrating disk to be placed +in a proper position. The point rests on the foil +under a pressure which must be regulated, and for +this purpose, as well as to detach the cylinder when +it is desired to place or take away the tinfoil, there +is the articulated system <span class="allsmcap">S N</span> which sustains the +support <span class="allsmcap">S</span> of the vibrating disk. This system consists +of a jointed lever in which there is a nut +screw for the screw <span class="allsmcap">R</span>. The handle <span class="allsmcap">N</span> at the end of +the lever allows the tracing system to be turned +aside when the screw <span class="allsmcap">R</span> is loosened. In order to +regulate the pressure of the tracing point on the +sheet of tinfoil, it is enough to turn the screw <span class="allsmcap">R</span> +loosely in its socket, and to tighten it as soon as +the right degree of pressure is obtained.</p> + +<p>This is the simple system by which speech can +engrave itself on a plate in durable characters, and +it works in the following manner.</p> + +<p><span class="pagenum" id="Page_316">316</span></p> + +<figure id="il_67" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p316.jpg" width="818" height="642" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 67.</span> + </figcaption> +</figure> + +<p>The speaker stands before the mouthpiece <span class="allsmcap">E</span>, +as before a telephone or an acoustic tube, and +speaks in a strong, emphatic voice, with his lips +pressed against the walls of the mouthpiece, as we +see in <a href="#il_67">fig. 67</a>; at the same moment he turns the +handle of the cylinder, which is provided with a +heavy fly-wheel in order that the movement may +be regular. Influenced by the voice, the plate <span class="allsmcap">L L</span> +begins to vibrate, and sets the tracing point at work, +which presses on the tinfoil at each vibration, and +produces a furrow whose depth varies along its +course in correspondence with the unequal vibrations +of the disk. The cylinder which moves at the same +time presents the different parts of the groove of +which we have spoken to the tracing point in succession;<span class="pagenum" id="Page_317">317</span> +so that when the spoken sentence comes +to an end, the design which has been pricked out, +consisting of a succession of reliefs and depressions, +represents the registration of the sentence itself. +The first part of the operation is therefore accomplished, +and by detaching the sheet from the instrument +the words may be put away in a portfolio. +We have now to see how the instrument is +able to reproduce what has been so easily inscribed.</p> + +<p>For this purpose it is only necessary to repeat +the process, and the identical effect will be reproduced +in an inverse sense. The tracing stylus is +replaced at the end of the groove it has already +traversed, and the cylinder is again set in motion. +When the engraved track passes again under the +point, it has a tendency to raise it and to impart to +it movements which must necessarily be the repetition +of those which first produced the tracing. +The vibrating plate is obedient to these movements, +and begins to vibrate, thus producing the same +sounds, and consequently the same words; yet +since there is necessarily a loss of power in this +double transformation of mechanical effects, the +speaking tube <span class="allsmcap">C</span> is attached to the mouthpiece <span class="allsmcap">E</span> +in order to intensify the effects. Under these conditions +the words reproduced by the instrument +may be heard in all parts of a hall, and it is startling +to hear this voice—somewhat shrill, it must +be admitted—which seems to utter its sentences +from beyond the grave. If this invention had<span class="pagenum" id="Page_318">318</span> +taken place in the middle ages, it would certainly +have been applied to ghostly apparitions, and it +would have been invaluable to miracle-mongers.</p> + +<figure id="il_68" class="figcenter" style="max-width: 28em;"> + <img src="images/i_p318.jpg" width="1087" height="906" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 68.</span> + </figcaption> +</figure> + +<p>As the height of the notes of the musical scale +depends on the number of vibrations effected by a +vibrating substance in a given time, speaking will +be reproduced in a tone of which the pitch will +depend on the velocity of rotation given to the cylinder +on which the tinfoil is wound. If the velocity +is the same as that which was used in registration,<span class="pagenum" id="Page_319">319</span> +the tone of the words reproduced is the +same as that in which they were uttered. If the +velocity is greater, the tone is higher; if less, the +tone is lower; but the accent of the speaker may +always be recognised. Owing to this peculiarity +the reproduction of songs is nearly always defective +in instruments turned by the hand; they sing out +of tune. This is not the case when the instrument +is moved by a well-regulated system of clockwork, +and in this way a satisfactory reproduction of a +duet has been obtained.</p> + +<p>The words registered on tinfoil can be often reproduced; +but the sounds become fainter and more +indistinct at each repetition, since the tracings in +relief are gradually effaced. The reproduction on +copper is more successful, but if intended to be +permanent the sheets must be stereotyped, and in +this case the instrument must be differently arranged.</p> + +<p>An attempt has been made to obtain speech +from the phonograph by taking the words registered +inversely to their true direction. In this way +the sounds obtained were necessarily quite unlike +the words uttered; yet Messrs. Fleeming Jenkin and +Ewing have observed that not only are the vowels +unchanged by this inverse action, but consonants, +syllables, and even whole words may be reproduced +with the accent they would have if spoken +backwards.</p> + +<p>The sounds produced by the phonograph,<span class="pagenum" id="Page_320">320</span> +although fainter than those of the voice which produced +the registered tracing, are strong enough to +react on the ordinary string telephone, and even on +a Bell telephone; and as in this case the sounds do +not go beyond the instrument, and can only be +heard by the person who is using it, it is easy to ascertain +that the sound has not been produced by +trickery.</p> + +<p>Mr. Edison presented his phonograph to the +Académie des Sciences through me, March 11, 1878, +and when his agent, M. Puskas, caused the wonderful +instrument to speak, a murmur of admiration was +heard from all parts of the hall—a murmur succeeded +by repeated applause. A letter appeared in the +newspapers from one of the persons present, in +which he said that ‘the learned Academy, generally +so cold, had never before abandoned itself to such +enthusiasm. Yet some members of a sceptical turn +of mind, instead of examining the physical fact, +ascribed it to moral causes, and a report soon ran +through the room which seemed to accuse the +Academy of having been mystified by a clever ventriloquist. +Certainly the spirit of ancient Gaul is +still to be found among the French, and even in +the Academy. One said that the sounds emitted +by the instrument were precisely those of a ventriloquist. +Another asked if the movements of M. +Puskas’ face and lips as he turned the instrument +did not resemble the grimaces of a ventriloquist. A +third admitted that the phonograph might emit<span class="pagenum" id="Page_321">321</span> +sounds, but believed that it was much helped by +the manipulator. Finally, the Academy requested +M. du Moncel to try the experiment, and as he +was not accustomed to speak into the instrument, +it was unsuccessful, to the great joy of the incredulous. +Some members of the Academy, however, +desiring to ascertain the real nature of the effects, +begged M. Puskas to repeat the experiments before +them in the secretary’s office under such conditions +as they should lay down. M. Puskas complied with +this request, and they were absolutely satisfied with +the result. Yet others remained incredulous, and +it was necessary that they should make the experiment +for themselves before they accepted the fact +that speech could be reproduced in so simple a way.’</p> + +<p>The anecdote I have just related cannot be interpreted +to the discredit of the Académie des +Sciences, since it is especially bound to preserve +the true principles of science intact, and only to +accept startling facts after a careful examination. +Owing to this attitude, all which emanates from the +Academy can be received with complete confidence; +and we cannot approve too highly of reserve which +does not give way to the first impulse of enthusiasm +and admiration.</p> + +<p>The failure of my experiment at the Academy +was simply due to the fact that I spoke at too +great a distance from the vibrating disk, and that +my lips did not touch the sides of the mouthpiece. +Some days later, at the request of several of my<span class="pagenum" id="Page_322">322</span> +colleagues, I made repeated trials of the instrument, +and I soon succeeded in making it speak as +well as the supposed ventriloquist; but I learned +at the same time that practice is necessary to ensure +success. Some words are reproduced more readily +than others; those which include many vowels +and many <i>r</i>’s come out better than those which +abound in consonants, and especially in <i>s</i>’s. It is +therefore not surprising that, even in the case of an +experienced manipulator like Mr. Edison’s agent, +some of the sentences uttered by him are more audible +than others.</p> + +<p>The simultaneous repetition of several sentences +in different languages by registering one over the +other is one of the most surprising effects of the +phonograph. As many as three different sentences +have been obtained; but in order to distinguish +them through the confused sounds which result +from placing one over the other, it is necessary that +different persons, giving special attention to a particular +sentence, should thus separate them and +understand their sense. Vocal airs may, in the +same way, be registered over the word tracings, and +in this case it is more easy to distinguish them.</p> + +<p>There are several models of phonographs. The +one represented in <a href="#il_66">fig. 66</a> has been chiefly used for +public experiments, but there is a small model, +generally sold to the public, in which the cylinder +is much longer, and serves at once for register +and fly-wheel. This instrument gives good +results, but can only be used for short sentences.<span class="pagenum" id="Page_323">323</span> +In this model, as indeed in the other, the words are +more easily registered by fastening a small tube in +the form of a prolonged speaking-trumpet to the +mouthpiece; the vibrations of the air are thus +concentrated on the vibrating disk, and act with +greater energy. The tenuity of the vibrating disk +adds to the efficiency of the instrument, and the +tracing point may be fitted directly to this disk.</p> + +<figure id="il_69" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p323.jpg" width="869" height="525" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 69.</span> + </figcaption> +</figure> + +<p>I need not describe particularly the phonograph +which acts by clockwork. The instrument resembles +the one represented <a href="#il_66">fig. 66</a>, except that it is mounted +on a rather high table, to give room for the descent +of the weight which moves the clockwork; the mechanism +is applied directly to the axis of the cylinder, +supplying the place of the winch, and is regulated +by a small fly-wheel. The wheel used in an +English system has been adopted, but we prefer +that of M. Villarceau, which has small wings.</p> + +<p><span class="pagenum" id="Page_324">324</span></p> + +<p>Since it is always difficult to fit the tinfoil to +the cylinder, Mr. Edison has tried, with good +success, to obtain the tracing on a plane surface of +tinfoil, by means of the arrangement represented +<a href="#il_69">fig. 69</a>. In this new model, the plate on which the +tin or copper sheet is to be applied has a spiral +grooving, of which one end corresponds to the +centre of the plate, and the other to its outer +edges. The plate is set in motion by a powerful +system of clockwork, of which the velocity is regulated +with reference to the length of the turns of +the spiral. The vibrating disk is arranged as in +the former instrument, and is placed above this +plate; the tracing point may, by means of a +movement of progression imparted to the system, +follow the spiral groove from the centre of the plate +to its circumference.</p> + +<p>It must not be supposed that all the tinfoil +used for phonographic registration is equally good. +The foil must be of a definite thickness, and combined +with a definite amount of lead. That which +is used for wrapping chocolate, and indeed all foil +of French manufacture, is too thin and too exclusively +made of tin to produce good results, and M. +Puskas was obliged to import some from America +to continue his experiments. The relative proportion +of lead and tin has not yet been defined, and +the selection of foil has been made empirically; +but as the use of the phonograph becomes more +general, this proportion must be ascertained, and<span class="pagenum" id="Page_325">325</span> +it may easily be done by analysing the composition +of the foil which gives the best results.</p> + +<figure id="il_70" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p325.jpg" width="850" height="831" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 70.</span> + </figcaption> +</figure> + +<p>The arrangement of the tracing point is also of +much importance for the successful action of the +phonograph. It must be very slender and very +short (not exceeding a millimètre in length), so as +to register distinctly the smallest vibrations of the +vibrating disk without deviating from the normal +direction of the cylinder, which might be the case, +if it were long, on account of the unequal friction +exerted on the tinfoil. It must also be made of a +metal which has no tendency to tear the metallic<span class="pagenum" id="Page_326">326</span> +sheet. Iron appears to combine most of the conditions +demanded.</p> + +<p>The phonograph is still in its infancy, and it is +probable that it may soon be enabled to register +speech without the necessity of speaking into a +mouthpiece. According to the newspapers, Mr. +Edison has already discovered a way of collecting, +without the aid of an acoustic tube, the sounds uttered +at a distance of three or four feet from the +instrument, and of printing them on a metallic sheet. +From this there is only a step to the power of inscribing +a speech uttered in a large hall at any +distance from the phonograph; and if this step is +taken, phonography may be substituted with advantage +for shorthand. We add in a note the instructions +given by M. Roosevelt to the purchasers +of phonographs, so as to enable them to work the +instrument.<a id="FNanchor_20" href="#Footnote_20" class="fnanchor">20</a></p> + +<p><span class="pagenum" id="Page_327">327</span></p> + +<p><i>Considerations on the theory.</i>—Although the explanation +we have given will make the effects of the<span class="pagenum" id="Page_328">328</span> +phonograph intelligible, it leads to a curious question +which has greatly interested physicists—namely, +how it is that the tracing made on so yielding a +surface as tin can, when retraced by the stylus, of +which the rigidity is relatively great, produce a +vibratory movement without being completely +destroyed. To this we reply that the retracing is +effected with such extreme rapidity that the effects +of active force which are developed only manifest +themselves locally, and that under these conditions +the mechanical effects exerted are as energetic in +soft as in hard substances. The curious experiment, +related in so many books on physics, must +be remembered, of a plank pierced when a candle +serves as the projectile of a gun. The various accidents +caused by the discharge of paper waddings +must also be remembered. Under such conditions +the motion imparted to the molecules which receive +the shock has not time to be transmitted to the +whole mass of the substance to which they belong, +and these molecules are compelled to separate from +it, or at any rate to produce, when the substance is +capable of vibration, a centre of vibration which +diffuses waves throughout its surface, and produces +sounds.</p> + +<p><span class="pagenum" id="Page_329">329</span></p> + +<p>Several scientific men, among others Messrs. +Preece and Mayer, have carefully studied the form +of the tracing left by the voice on the tinfoil of the +phonograph, and they observe that it greatly resembles +the outline of the singing flames so well +shown by Herr Koenig’s instruments. Mr. Mayer +wrote on this subject in the ‘Popular Science +Monthly Review’ of April 1878.</p> + +<p>He said that he had been successful in reproducing +a splendid tracing on smoked glass, which +gave in profile the outline of the vibrations of sound +registered on the tinfoil with their varying curves. +For this purpose he fastened to the spring support +of the tracing point of the phonograph a slender +rod, terminating in a point, which pressed obliquely +against the plate of smoked glass, and, since the +latter was in a vertical position, a movement imparted +to the rod enabled it to produce a sinusoidal +tracing. By this arrangement, when the phonograph +was at work, two systems of tracings were +produced at the same moment, of which one was +the profile of the other.</p> + +<p>Mr. Mayer had not, at the time he wrote, been +long enough in possession of the instrument to +make many experiments with it, but from a study +of some of its curves it appeared to him that the +registered outlines bore a strong resemblance to +those of Koenig’s singing flames.</p> + +<figure id="il_71" class="figcenter" style="max-width: 21em;"> + <img src="images/i_p330.jpg" width="813" height="347" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 71.</span> + </figcaption> +</figure> + +<p><a href="#il_71">Fig. 71</a> represents the tracing which corresponds +to the letter <i>a</i> when pronounced as in <em>bat</em>, in the<span class="pagenum" id="Page_330">330</span> +three systems of registration. That corresponding +to line A is an enlarged reproduction of the tracing +left on the tinfoil; that corresponding to line B +represents its profile on the sheet of smoked glass. +Finally, line C shows the outline of Koenig’s singing +flames, when the same sound is produced quite +close to the membrane of the register. It must be +quite close, since the form of the tracing produced +by a pointer attached to a vibrating membrane, +when influenced by composite sounds, depends on +the distance intervening between the membrane +and the source of sound, and an infinite variety in +the form of the tracing may be obtained by modifying +the distance. In fact, when this distance is +increased, the waves of sound which result from +composite sounds react on the membrane at +different moments of their emission. For example, +if the composite sound is formed of six harmonics, +the displacement of the source of vibration from +the first harmonic by ¼ the length of a wave will +respectively remove the second, third, fourth, fifth,<span class="pagenum" id="Page_331">331</span> +and sixth harmonics ½, ¾, 1, 1¼, 1½ the length of a +wave, and consequently the outline resulting from the +combination of waves will no longer be the same as +it was before the displacement of the source of sound, +although the perception of the sounds remains the +same in both cases. This principle is clearly +demonstrated by Koenig’s instrument, by lengthening +and shortening an extensible tube, inserted +between the resonator and the vibrating membrane, +which is placed close to the flame; and this explains +the disagreement of physicists as to the composition +of vocal sounds which they have analysed by +means of the singing flames.</p> + +<p>Mr. Mayer adds that these facts further show +that we cannot hope to read the impressions and +tracings of the phonograph, which not only vary +with the nature of the voice, but also with the +different moments at which the harmonics of the +voice are emitted, and with the relative differences +in the intensities of these harmonics.</p> + +<p>Notwithstanding this assertion, we reproduce +(<a href="#il_72">fig. 72</a>) an extremely curious tracing sent to us by +Mr. Blake, which represents the vibrations produced +by the words ‘Brown, University: how do +you do?’ They were photographed by means of +an index fastened to a vibrating disk on which a +ray of light was thrown. The word ‘how’ is +particularly remarkable for the combined forms of +the inflections of the vibrations.</p> + +<p>Recent experiments seem to show that the more<span class="pagenum" id="Page_332">332</span> +the vibrating membrane of the phonograph +resembles the human ear in its construction, the +better it repeats and registers the sound vibrations: +it should be stretched, as far as possible, in the +same way as the tympanum is stretched by the +hammer of the ear, and moreover it should have +the same form, since the vibrations of air are in +this case much more effective.</p> + +<figure id="il_72" class="figcenter" style="max-width: 24em;"> + <img src="images/i_p332.jpg" width="931" height="795" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 72.</span> + </figcaption> +</figure> + +<p>Mr. Edison considers that the size of the opening +of the mouthpiece has considerable influence +on the distinct articulation of speech. When the +sounds are pronounced before the whole surface of<span class="pagenum" id="Page_333">333</span> +the diaphragm, some hissing sounds are lost. They +are, on the contrary, intensified when these sounds +reach the diaphragm through a narrow orifice with +sharp rims. If the opening is toothed on its flattened +rims, the hissing consonants are delivered +more clearly. Speech is reproduced more perfectly +when the mouthpiece has a covering of some thickness, +so arranged as to deaden the sounds arising +from the friction of the tracing point on the tin.</p> + +<p>Mr. Hardy has rendered the registration of +phonographic tracings more easy by adding a small +ebonite tube, resembling the mouthpiece of a wind +instrument, to the mouthpiece of the phonograph.</p> + +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<h2 class="nobreak" id="USES_OF_THE_PHONOGRAPH_AND_ITS_FUTURE"><span id="toclink_333"></span>USES OF THE PHONOGRAPH AND ITS FUTURE.</h2> +</div> + +<p>Mr. Edison has lately published in the ‘North +American Review’ of May-June 1878 an article on +the future of the phonograph, in which he himself +discusses the different applications which may be +made of this instrument. Without sharing all his +anticipations, which appear to us to be very premature, +we think that some extracts from his paper +may be interesting.</p> + +<p>‘In order to furnish a basis on which the +reader may take his stand ... a few categorical +questions and answers are given upon the essential +features of the principle involved.</p> + +<p>‘1. Is a vibrating plate or disk capable of receiving +a complex motion which shall correctly represent<span class="pagenum" id="Page_334">334</span> +the peculiar property of each and all the +multifarious vocal and other sound waves?</p> + +<p>‘The telephone answers affirmatively.</p> + +<p>‘2. Can such complex movement be transmitted +from such plate by means of a single embossing +point attached thereto, to effect a record +upon a plastic material, by indentation, with such +fidelity as to give to such indentations the same +varied and complex form? And if so, will this +embossing point, upon being passed over the record +thus made, follow it with such fidelity as to transmit +to the disk the same variety of movement, and +thus effect a restoration or reproduction of the +vocal or other sound waves, without loss of any +property essential to producing on the ear the +same sensation as if coming direct from the original +source?</p> + +<p>‘The answer to this may be summed up in +a statement of the fact that ... the writer has +at various times during the past weeks reproduced +these waves with such degree of accuracy in each +and every detail as to enable his assistants to read, +without the loss of a word, one or more columns of a +newspaper article unfamiliar to them, and which +were spoken into the apparatus when they were +not present. The only perceptible loss was found +to be in the quality of the utterance, a non-essential +in the practical application of the instrument. +Indeed, the articulation of some individuals has +been perceptibly improved by passage through the<span class="pagenum" id="Page_335">335</span> +phonograph, the original utterance being mutilated +by some imperfection of lip and mouth formation, +and these mutilations corrected or eliminated by +the mechanism of the phonograph.<a id="FNanchor_21" href="#Footnote_21" class="fnanchor">21</a></p> + +<p>‘3. Can a record be removed from the +apparatus on which it was made, and replaced +upon a second without mutilation or loss of +effective power to vibrate the second plate?</p> + +<p>‘This is a mere mechanical detail, presenting +no greater obstacle than having proper regard for +the perfect interchangeableness of the various +working parts of the apparatus—not so nice a +problem as the manufacture of the American +watch.</p> + +<p>‘4. What as to the facility of placing and removing +the second sheet, and as to its transportation +by mail?</p> + +<p>‘But ten or fifteen seconds suffice for such placing +or removing. A special envelope will probably +be required, the weight and form of which, however, +will but slightly increase the cost of postage.</p> + +<p>‘5. What as to durability?</p> + +<p>‘Repeated experiments have proved that the +indentations possess wonderful enduring power, +even when the reproduction has been effected by +the comparatively rigid plate used for their +production. It is proposed, however, to use a<span class="pagenum" id="Page_336">336</span> +more flexible plate for reproducing, which, with a +perfectly smooth stone point—diamond or sapphire—will +render the record capable of from fifty to +one hundred repetitions, enough for all practical +purposes.</p> + +<p>‘6. What as to duplication of a record and its +permanence?</p> + +<p>‘Many experiments have been made, with +more or less success, in the effort to obtain electrotypes +of a record, and the writer is informed that it +has very recently been successfully accomplished. +He can certainly see no great practical obstacle in +the way. This, of course, permits of an indefinite +multiplication of a record, and its preservation for +all time.</p> + +<p>‘7. What is the requisite force of wave impinging +upon the diaphragm, and the proximity of the +mouth to the diaphragm, to effect a record?</p> + +<p>‘These depend in great measure upon the +volume of sound desired in the reproduction. If +the reproduction is to be made audible to an +assembly, considerable force is requisite in the +original utterance; if for the individual ear, only +the ordinary conversational tone (even a whisper +has been reproduced). In both cases the original +utterances are delivered directly in the mouthpiece +of the instrument. An audible reproduction +may, however, be had by speaking at the instrument +from a distance of from two to three feet in loud +tone. The application of a flaring tube or funnel +to collect the sound waves, and the construction of<span class="pagenum" id="Page_337">337</span> +an especially delicate diaphragm and embossing +point, &c., are the simple means which suggest +themselves to effect this....</p> + +<p>‘The foregoing presentment of the stage of +development reached by the several essential +features of the phonograph demonstrates the +following <i lang="fr">faits accomplis</i>:</p> + +<p>‘1. The captivity of all manner of sound +waves, hitherto designated as “fugitive,” and their +retention.</p> + +<p>‘2. Their reproduction with all their original +characteristics, without the presence or consent +of the original source, and after the lapse of any +period of time.</p> + +<p>‘3. The transmission of such captive sounds +through the ordinary channels of commercial intercourse +and trade in a material form, for purposes of +communication.</p> + +<p>‘4. Indefinite multiplication and preservation +of such sounds, without regard to the existence or +non-existence of the original source.</p> + +<p>‘5. The captivation of sounds, with or without the +knowledge or consent of the source of their origin...</p> + +<p>‘The apparatus now being perfected in +mechanical details will be the standard phonograph, +and may be used for all purposes, except +such as require special form of matrix, such as +toys, clocks, &c., for an indefinite repetition of the +same thing. The main utility of the phonograph +being, however, for the purposes of letter-writing<span class="pagenum" id="Page_338">338</span> +and other forms of dictation, the design is made +with a view to its utility for that purpose.</p> + +<p>‘The general principles of construction are, a flat +plate or disk, with spiral groove on the face, worked +by clockwork underneath the plate; the grooves are +cut very closely together, so as to give a great total +length to each length of surface—a close calculation +gives as the capacity of each sheet of foil nearly +40,000 words. The sheets being but ten inches +square, the cost is so trifling that but a hundred words +might be put on a single sheet economically....</p> + +<p>‘The practical application of this form of +phonograph is very simple. A sheet of foil is +placed in the phonograph, the clockwork set in +motion, and the matter dictated into the mouthpiece +without other effort than when dictating to a +stenographer. It is then removed, placed in suitable +form of envelope, and sent through the +ordinary channels to the correspondent for whom +it is designed. He, placing it upon his phonograph, +starts his clockwork, and <em>listens</em> to what his +correspondent has to say.’</p> + +<p>Since this paper by Mr. Edison appeared in +June 1878, he has applied the phonograph to +several other purposes, among which we may +mention that of registering the force of sounds on +railways, and especially on the metropolitan +atmospheric railway in New York. The instrument +which he has made for this purpose resembles +that by Mr. Leo Scott, and bears the same name.<span class="pagenum" id="Page_339">339</span> +It is described and represented in the ‘Daily +Graphic’ of July 19, 1878, as well as the aerophone, +the megaphone, and the microtasimeter, which is +adapted for astronomical observations. We should +exceed the limits laid down for this volume, if we +were to give a more detailed account of these +inventions.</p> + +<p>M. Lambrigot, one of the officials on the +telegraphic lines in France, and the author of +various improvements in the Caselli telegraph, has +shown me a phonographic system of his own +invention in which it is reduced to its simplest +form. He sent me the following description of his +system.</p> + +<p>‘The instrument consists of a wooden slab +placed vertically on a stand and firmly fixed upon +it. There is a round opening in the middle of the +slab, covered by a tightly stretched sheet of +parchment bearing a steel knife, which, like the +tracing point of the phonograph, is intended to +trace the vibrations. A solid block rises from +the stand to the middle of the slab, and supports a +slide on which a runner can move in front of the +slab. There is a strip of glass on this runner, of +which one side is covered with stearine. When the +runner is moved to and fro, the stearine comes in +contact with the knife and takes the mould of its +form, which is curved throughout.</p> + +<p>‘A sound places the sheet of parchment in +vibration, and imparts its movement to the knife,<span class="pagenum" id="Page_340">340</span> +which traces various lines on the surface of the +stearine.</p> + +<p>‘The reproduction thus obtained on the strip of +glass is subjected to the ordinary processes of metallisation. +By galvanism a deposit of copper is +obtained which reproduces the lines in an inverse +way. In order to make the metallic plate speak, +it is necessary to pass a point of ivory, wood, +or horn lightly over the signs, and, by moving it +more or less quickly, the different tones can be +heard, just as they were spoken.</p> + +<p>‘Since copper is relatively harder than lead, the +copper plate on which the vibrations are traced +will afford an unlimited number of reproductions. +To obtain this result, a lead wire must be applied +to the plate, and due pressure must be exerted on +it. The wire is flattened and takes the impression +of all the traces which then appear in relief. +If the edge of a card is passed through this impressed +tracing, the same sounds are produced as +those which are obtained from the copper plate.’</p> + +<p>M. Lambrigot suggests that the speaking plates +might be useful in many ways: for example, they +might make it easy to learn the correct pronunciation +of foreign languages, since a sufficient number +might be collected to make a sort of vocabulary +which would give the accent of the words most in +use in a given language.</p> + +<p>By this simple process M. Lambrigot has been +able to obtain a strong impression, within a copper<span class="pagenum" id="Page_341">341</span> +groove, of the vibrations caused by the voice, and +they are so distinctly engraved that whole sentences +may be heard, if they are retraced by the sharpened +point of a match. It is true that the reproduction +is imperfect, and that those words are only to be +distinguished which were previously known; but it +is possible that better results will be obtained from +improvements in the system, and at any rate +the distinct impression of the vibrations of the +voice on a hard metal is a really interesting discovery.</p> + +<p>I have made one somewhat important observation +in the working of the phonograph—namely, +that if speech is registered on the instrument in a +very hot room, and it is then carried to a colder +room, the reproduction of speech is imperfect in proportion +to the difference of temperature. This is +probably owing to considerable modifications in the +elasticity of the caoutchouc pad which is inserted +between the tracing point and the vibrating disk: +perhaps differences of expansion in the tinfoil +have also some effect.</p> + +<hr class="chap x-ebookmaker-drop"> + +<h2>FABER’S AMERICAN SPEAKING MACHINE.</h2> + +<p>About two years ago the newspapers announced +with some pomp that a speaking machine had +reached Paris, which far surpassed Vaucanson’s +duck, and which would attract general attention. +Unfortunately the invention was not in the first<span class="pagenum" id="Page_342">342</span> +instance brought forward with any scientific +authority, and was soon relegated to take a place +among the curiosities exhibited by conjurors. In +a country so essentially critical and sceptical as +France, there are always those who profess incredulity, +and who will even resist evidence, and it was +asserted that the machine only spoke because its +exhibitor was an able ventriloquist. This is an old +assertion which has lately been made with reference +to the phonograph. Some scientific papers echoed +the absurdity, and the speaking machine was so +discredited that it is now unnoticed, although it is a +most ingenious and interesting conception. When +will our country be cured of the error of denying +everything without due examination?</p> + +<p>Since we ourselves only judge of things after +having seriously considered them, we think it just +to vindicate the truth as to Mr. Faber’s machine, +and this can only be done by an exact description +of it.</p> + +<p>As I said in the last chapter, there is a great +difference between the production and the reproduction +of a sound, and a machine like the phonograph, +adapted for the reproduction of sound, +may differ essentially from a machine which really +speaks. In fact, the reproduction even of articulate +sounds may be very simple, as soon as we possess +the means of stereotyping the vibrations of air +necessary to transmit these sounds; but in order +to produce them, and especially to emit the complex<span class="pagenum" id="Page_343">343</span> +vibrations which constitute speech, it is +necessary to set in motion a number of special +organs, fulfilling more or less exactly the functions +of the larynx, the mouth, the tongue, the lips, and +even the nose. For this reason, a speaking machine +is necessarily very complicated, and this is precisely +the case with the machine we are now considering. +Such a machine is not now made for the first time, +and the Academy has lately been reminded of a +speaking head which was in the possession of the +philosopher Albertus Magnus in the thirteenth +century, and which was destroyed by St. Thomas +Aquinas as a diabolical invention.</p> + +<p>Mr. Faber’s speaking machine was exhibited two +years ago at the Grand Hôtel, and may now be seen +in the room adjoining M. Robert Houdin’s theatre, +the same room in which Mr. Giffard exhibited the +telephone. It consists of three distinct parts: 1st, +of a large bellows worked by a pedal, which produces +the currents of air necessary for the production +of sounds, and to some extent acts as the +lungs; 2nd, a vocal instrument, consisting of a +larynx accompanied by diaphragms of various +forms to modify the sounds, of a mouth with +caoutchouc lips and tongue, and of a tube with an +outlet somewhat resembling the nasal cavities; +3rd, of a system of jointed levers and of pedals, +terminating in keys like those of a piano.</p> + +<p>The most interesting part of the machinery, of +which we represent the principle <a href="#il_73">fig. 73</a>, is the<span class="pagenum" id="Page_344">344</span> +vocal apparatus, which involved the severest study +of physics in order to succeed in the production of +articulate sounds. It consists, first, of a rather +thick caoutchouc tube, within which there is a kind +of whistle <span class="allsmcap">L</span>, as in a clarionet. The whistle consists +of a small caoutchouc cylinder with a longitudinal +slit, and before this is placed a very thin ivory +plate lined with caoutchouc. This plate is fixed +at one end to the cylinder, and deviates slightly +from it at its free end, so as to permit the current +of air projected from the bellows <span class="allsmcap">S</span> to penetrate +between the two parts, and to cause the vibrations +in the ivory plate necessary for the production of +a sound. The extremity of the caoutchouc cylinder +is closed on this side, and is fitted to an iron rod <i>t</i> +which comes out of the pipe, and is connected +with a system of bars, corresponding to the keyboard +of a piano, by which the force of sounds +can be regulated. This force depends on the width +of the opening between the tongue and the cylinder.</p> + +<figure id="il_73" class="figcenter" style="max-width: 22em;"> + <img src="images/i_p345.jpg" width="863" height="764" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 73.</span> + </figcaption> +</figure> + +<p>The whistle, which plays the part of the +larynx, is necessarily placed opposite the opening of +the bellows, and a sort of tourniquet <span class="allsmcap">M</span> is fastened +to the opening itself, which is able to move on +certain conditions, so that it may produce the +rolling sound of <i>r</i>. This is done by fastening before +the opening a diaphragm in which there is a somewhat +wide and long slit, and this slit can be almost +closed by a little bar of the same size <span class="allsmcap">M</span>, revolving +on a transverse axis which supports it by its<span class="pagenum" id="Page_345">345</span> +centre. In its normal condition, this little bar is +kept in a slanting position by cords attached to +the keyboard, and the air ejected by the bellows +readily traverses the slit in order to reach the +larynx; but two dampers are fastened to the rods +which transmit movement, with which the cords +just mentioned are also connected. On lowering +the notes of the key-board, the passage of air is contracted, +and the little plate begins to oscillate and to +press against a band of leather, producing by its +vibration an action similar to that produced by the +cricket. This little tourniquet only begins to act +when the dampers are lowered by a pedal worked<span class="pagenum" id="Page_346">346</span> +by the hand; and this is also the case with the iron +rod <i>t</i>, which modifies the acuteness of the sounds +passing through the larynx.<a id="FNanchor_22" href="#Footnote_22" class="fnanchor">22</a></p> + +<p>Below the larynx tube, which is only five +centimètres in length, there is another pipe <span class="allsmcap">G</span>, +also of caoutchouc, which terminates in a spherical +cavity connected with the outer air by a caoutchouc +tube <span class="allsmcap">I</span>, slightly raised, and closed by a valve, of +which the movements are regulated by a pedal +worked by the keyboard. When the valve is +open, the sounds emitted through the larynx are +somewhat nasal.<a id="FNanchor_23" href="#Footnote_23" class="fnanchor">23</a> The larynx communicates with +the mouth through a square funnel-shaped pipe, +to which six metallic diaphragms <span class="allsmcap">D</span> are fastened; +the diaphragms are placed in a vertical position +behind each other, and have indentations on their +lower end, which are intended to diminish more or +less the orifice for the current of air, and to impede +its passage with greater or less force. The diaphragms, +which we represent separately <a href="#il_74">fig. 74</a>, are +connected with the keyboard by jointed iron rods <i>t</i>, +and, for the emission of most articulate sounds,<span class="pagenum" id="Page_347">347</span> +several of the diaphragms are moved at the same +moment and at different heights. We shall return +to this subject.</p> + +<figure id="il_74" class="figcenter" style="max-width: 18em;"> + <img src="images/i_p347.jpg" width="719" height="726" alt=""> + <figcaption class="caption"><span class="smcap">Fig. 74.</span> + </figcaption> +</figure> + +<p>The mouth consists of a caoutchouc cavity <span class="allsmcap">O</span>, +somewhat resembling the human mouth, and forming +a continuation to the channel we have just described. +The tongue <span class="allsmcap">C</span>, likewise modelled on the human +tongue, is placed within the mouth, and connected +with two jointed rods <i>t</i>, <i>t</i>, fastened to its two +opposite ends, so as to enable the tongue to raise +its tip, or touch the palate, in obedience to the +notes of the keyboard. The lower caoutchouc lip +<span class="allsmcap">A</span> can also be more or less closed, according to the<span class="pagenum" id="Page_348">348</span> +action of the keyboard on its special rod. Finally, +a circular metallic piece <span class="allsmcap">E</span>, following the shape of +the mouth, is placed above the upper lip, with a +small opening in it to admit of the pronunciation +of the letter <i>f</i>.</p> + +<p>The keyboard has fourteen notes, of different +lengths, producing the following letters when +lowered, <i>a</i>, <i>o</i>, <i>u</i>, <i>i</i>, <i>e</i>, <i>l</i>, <i>r</i>, <i>v</i>, <i>f</i>, <i>s</i>, <i>ch</i>, <i>b</i>, <i>d</i>, <i>g</i>. The +longest corresponds to <i>g</i>, and the shortest to <i>a</i>. +There are two pedals below the <i>g</i> note and those +of <i>b</i> and <i>d</i>, corresponding with the opening of the +tube which produces nasal sounds, and to the rod +which regulates the opening of the larynx, and +this makes it possible to obtain <i>p</i>, <i>t</i>, and <i>k</i> from the +notes <i>b</i>, <i>d</i>, <i>g</i>. The mechanical effects produced by +lowering the different notes in succession are as +<span class="locked">follows:—</span></p> + +<p>1. The <i>a</i> note moves the first five diaphragms.</p> + +<p>2. <i>o</i> also moves these five diaphragms, but +varies the pitch, and closes the mouth a little.</p> + +<p>3. <i>u</i> does the same, only further closing the +mouth.</p> + +<p>4. <i>t</i> moves a single diaphragm, raises the tip of +the tongue, and opens the mouth more widely.</p> + +<p>5. <i>e</i> moves six diaphragms, throws the tongue +further back, and opens the mouth still more.</p> + +<p>6. <i>l</i> moves five diaphragms, sends the tongue +against the palate, and further opens the mouth.</p> + +<p>7. <i>r</i> moves six diaphragms and the tourniquet, +lowers the tongue, and somewhat closes the mouth.</p> + +<p><span class="pagenum" id="Page_349">349</span></p> + +<p>8. <i>v</i> moves five diaphragms, almost closes the +mouth, and keeps the tongue down.</p> + +<p>9. <i>f</i> lowers the circular appendix of the upper +lip, and almost entirely closes the mouth.</p> + +<p>10. <i>s</i> moves three diaphragms, half closes the +mouth, and half raises the tongue.</p> + +<p>11. <i>ch</i> moves three diaphragms, keeps the +mouth half closed, and further lowers the tongue.</p> + +<p>12. <i>b</i> moves five diaphragms, closes the mouth, +and keeps the tongue completely down.</p> + +<p>13. <i>d</i> moves six diaphragms, keeps the mouth +three parts closed, and raises the tongue a little.</p> + +<p>14. <i>g</i> moves five diaphragms, keeps the mouth +three parts closed, and the tongue completely down.</p> + +<p><i>m</i> is produced by lowering note <i>b</i> and opening +the valve of the pipe which gives nasal sounds.</p> + +<p><i>n</i> is obtained by lowering note <i>d</i> and opening +the same valve.</p> + +<p><i>h</i> is obtained from note <i>s</i> by lowering the pedal +which acts upon the larynx, and half closing it.</p> + +<p>Since the other letters of the alphabet are compound +sounds, they can be produced by combinations +of the preceding letters.</p> + +<p>Although the words pronounced by this +machine are distinct, they are spoken in a uniform, +drawling tone, which might, I should have thought, +have excluded the idea of imposition. Some of +them are indeed far from distinct, yet the results +are not less remarkable; and when we consider the +amount of study and experience which must have<span class="pagenum" id="Page_350">350</span> +been applied to the combination of all these +arrangements, it seems surprising that physicists +have not given more attention to such an interesting +machine.</p> + +<p>As for the mechanical execution, it is impossible +to admire too highly the simple and ingenious +manner in which all the complicated movements +of the different vocal organs have been connected +with the keyboard, of which the mechanism has +been so calculated as only to produce the precise +action of the organ which is required for any +given effect. For this purpose, the notes of the +keyboard regularly increase in length, so as to +produce at a single touch different mechanical +effects on the rods which act upon the mechanism; +and since most of the notes are required to react +simultaneously on the whole mechanism, the rods +which transmit the movement are fastened to a +series of jointed levers which cross the notes of the +keyboard at right angles. Pegs of different length +are fastened to the notes at this junction, so as to +produce the simultaneous action of the different +organs of the machine.</p> + +<p>The public will believe that the assertions of +ventriloquism are unfounded when I add that I +myself have made the machine speak.</p> +<hr class="chap x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_351">351</span></p> + +<h2 class="nobreak" id="APPENDIX"><span id="toclink_351"></span>APPENDIX.</h2> +</div> + +<p><i>The Perrodon System of Telephonic Alarum.</i>—Captain +Perrodon, of the French Artillery, has lately improved the +system invented by MM. Dutertre and Gouault, by a +self-acting call. For this purpose he has fastened a spring +contact before the diaphragm, combined with the diaphragm +and the electro-magnetic system so as to form a +vibrator. The vibrations thus produced are strong +enough to resound in an ordinary telephone, so as to +make the call audible in spite of external noises.</p> + +<p>The system has been arranged in different ways. In +one arrangement, a small plate of tinfoil is glued to the +outer surface of the diaphragm, and the end of the telephone +coil wire is connected, below the inner surface of +the mouthpiece, with a silver wire soldered to a spring +plate, which constitutes the contact of the vibrator. This +spring plate, slightly curved, is fixed below one of the +binding-screws of the telephone, and terminates at its +free end in a regulating screw by which the interval +between the contacts can be regulated, and the instrument +can be arranged as a telephonic organ. To do this, the +screw can be withdrawn, and inserted in a nut which +establishes direct connection between the line and the<span class="pagenum" id="Page_352">352</span> +telephone coil. It is easy to adapt an ordinary telephone +to this system.</p> + +<p>In another arrangement M. Courtot’s mirror telephone +has been employed, and a sort of spring pedal is inserted +in the wood of the mouthpiece, which terminates in a +bent silver wire, supporting an index adapted to make a +contact with a square plate soldered to the diaphragm. +The battery is placed in connection with the spring of the +pedal, and one end of the telephone coil-wire communicates +as before with the diaphragm. When a call is to be +made, the pedal must be pressed, and the battery immediately +communicates with the silver wire which, with +the diaphragm, constitutes the vibrator, and an electric +vibration is sent through the circuit, and produces the +call. For receiving, the pedal is allowed to revert to its +normal position, and the index of the pedal, touching +the contact in connection with the diaphragm, establishes +direct communication between the two telephones, while +breaking the contact of the silver wire with the diaphragm, +so that the battery cannot act.</p> + +<p>It appears that experiments made at the musketry +school at Orleans for a distance of 370 miles have been +very successful.</p> + +<p><i>M. Varey’s Microphone Speaker.</i>—M. Varey has +recently arranged a successful microphonic speaker, in +which the principle of the microphone represented in <a href="#il_39">fig. 39</a> +is maintained. The system of three vertical carbons is +arranged inside a sort of snuff-box, of which the lid is +made of a thin plate of mica, horn, or ebonite. The +snuff-box is provided with two hinged arms, so that it +may be placed in the most convenient position for speaking, +and at the same time the sensitiveness of the instrument +can be regulated. A small battery, consisting of +two Gaiffe cells of chloride of silver, is placed in the<span class="pagenum" id="Page_353">353</span> +pedestal on which the instrument stands, and sets the +microphone at work without further trouble. In this +way the speaker can be used like an ordinary telephone, +and is not affected by vibrations of air. Only vibrations +of sound react upon it.</p> + +<p><i>Microphonic Speaker by Fitch.</i>—Mr. Pope states that +this speaker has produced excellent results in America. +It is merely Edison’s carbon telephone reduced to its +simplest form. It consists of a small cylindrical box, +which has a mouthpiece like the one represented <a href="#il_28">fig. 28</a>. +The box contains two carbon disks of the same diameter +as itself, and is lined with a kind of felt. Metal wires, +inlaid in a groove scooped on the circumference of the +carbons, place them in communication with the circuit +and battery, and transmission takes place by means of the +vibrations of the upper carbon, which is directly influenced +by the voice without the intervention of any diaphragm. +These vibrations, which can be freely developed in consequence +of the elasticity of the felt pad which supports +the lower carbon, produce on the surface of contact of +the two carbons the modifications of intensity of current +necessary for the reproduction of speech, in the same way +as other microphones.</p> + +<p>An induction coil is necessarily employed for a long +circuit, and the effects of induction in the adjacent +wires are modified by two rheostats introduced into the +circuit at its two extremities.</p> + +<p><i>Further remarks on the theory of the Telephone.</i>—Following +the example of a certain sceptic in the Académie +des Sciences, Colonel Navez continues to maintain the +theory first formed as to the mode in which the telephone +acts, in spite of the clearest proofs of its insufficiency; +but most scientific men who consider the question have +come round to our opinion, and admit the concurrence<span class="pagenum" id="Page_354">354</span> +of several causes in the reproduction of speech by this +remarkable instrument. Mr. Fleeming Jenkin writes to +this effect in the new edition of a treatise on Electricity +and Magnetism.</p> + +<p>He observes that a singular fact has been discovered +by several persons, who have ascertained that not merely +non-magnetic and non-conducting bodies can be substituted +for the diaphragms of receiving telephones, but +that they will act without a diaphragm at all. In this +case it is evident that we have to do with the sounds +discovered by Page, and that they are produced by the +magnet itself, in which each molecular movement constitutes +the source of the sound produced. This sound +becomes articulate as soon as its increase and decrease +can follow the increasing or decreasing action of the voice +which produces it at the sending station. It is certain +that when the transmitted currents are due to the action +of the Bell diaphragm, the sounds due to the Page effects +ought to correspond with those which would be given by +iron diaphragms adapted to the receiving instruments; +so that, when a telephone has an iron diaphragm, there are +in fact two voices, that of the diaphragm, which is strong, +and that of the magnet, which is weak. When a disk of +wood is substituted for one of iron, it acts as a sounding +board for the Page effect, and when the disk is of metal, +induction is developed by the magnetic modifications, and +tends to produce vibration, thus developing a third source +of sound, which may be called the Ampère effect. +Finally, a fourth source of sound may result from the +induced effects produced in the wire itself in consequence +of changes in the intensity of current. These sounds, +first observed by M. de la Rive, have since been studied +by Mr. Fergusson of Edinburgh (vide ‘Telegraphic +Journal’ of November 1, 1878).</p> + +<p><span class="pagenum" id="Page_355">355</span></p> + +<p>Mr. Fleeming Jenkin’s opinion only differs from mine +in his ascribing the energy of sound acquired by a telephone +with an iron diaphragm to the preponderance of +sounds in the latter, whereas I consider it to be chiefly +due to the increase of energy in the whole magnetic +system produced by the reaction of the two magnetic +parts on each other. If the two effects could be taken +singly, it is probable that the sounds produced by each +of them separately would be similar, since in magnetic +effects the reaction and action are equal. But as +they are combined, it becomes difficult to assign to each +the share which belongs to it in the general effect +observed. Besides, it is quite possible that the sounds +of the diaphragm may appear to be stronger and more +distinct because it is nearer to the ear than the magnet, +and because the effects of magnetisation and demagnetisation +are then more easily produced in consequence of +the mass of the magnetic body being smaller.</p> + +<p>Mr. Fleeming Jenkin goes on to say that the question +of the displacement of surface in the diaphragm and +magnet is very complex, but that he thinks it impossible +to deny the existence of such displacement, since the air +which acts as the vehicle of sound between the ear and +the source of sound is placed in vibration; yet this displacement +maybe effected quite otherwise than by flexion. +Suppose that the magnetic molecules of these bodies are +drawn together by magnetisation, which tends to diminish +the intermolecular space which separates them, the points +of surface of the substance corresponding to these intervals +will be elevated in a manner equivalent to a displacement +of surface, and the effect of this will be the +same as a flexion movement. At the moment of demagnetisation +a depression instead of an elevation will take +place, and the vibratory movements will thus be produced<span class="pagenum" id="Page_356">356</span> +without any electro-magnetic attraction, and it is precisely +these vibrations which Mr. Fleeming Jenkin terms molecular +vibrations. He evidently does not mean that such +attractions cannot take place: they may react, together +with the molecular vibrations, when the electric force is +capable of producing them. He adds that the reproduction +of sounds by a condenser, by simple coils, and by a +carbon microphone, has convinced him that the action +just analysed requires generalisation.</p> + +<p>We have recently seen an article by Mr. Hughes in +the ‘Telegraphic Journal,’ Nov. 15, 1878, in which, to our +surprise, he not only opposes all the theories he has +hitherto held, but cites experiments which are quite +inconclusive, since they were performed under conditions +in which electro-magnetic effects must necessarily be displayed. +He made use of voltaic currents produced by a +battery of three Daniell cells. In order to estimate the +transverse effects resulting in such a case from attraction, +the experiments he mentions are wholly unnecessary: +they may be felt with the hand. On the other hand, he +has evidently forgotten that the currents employed in a +Bell telephone have no influence on a very sensitive +galvanometer.</p> + +<p><i>M. Pollard’s Microphone.</i>—This microphone, which +has been arranged in several ways, essentially consists of +a carbon rod kept in a horizontal position by a wire, and +resting on two other vertical carbons. The upright of +the arm which holds the wire can revolve together with +this arm, and is thus able to regulate the pressure of the +horizontal carbon on the two vertical carbons. It appears +that this instrument is extremely sensitive, and that the +regulation effected on the two contacts is better than when +it is effected on one only. It is fair to add that M.<span class="pagenum" id="Page_357">357</span> +Voisin previously sent me the sketch of a somewhat +similar arrangement.</p> + +<p>M. Dutertre has also made use of such an arrangement +in what he calls the Dolmen microphone. Three +pieces of coke in the form of a dolmen, that is, two uprights, +supporting a third and horizontal carbon, are +placed in circuit. M. Gouault has informed me that +speech was well transmitted by this instrument, and it is, +like that of Mr. Blyth, which succeeded it, of wonderful +simplicity.</p> + +<p>This microphone, as well as one composed of two +pieces of lead-pencil placed in a watch-case, and connected +by a piece of money, were exhibited to the +Industrial Society at Rouen, February 1, 1878, of which +an account was published in the Bulletin of that society.</p> + +<p><i>M. Ader’s Electrophone.</i>—M. Ader has recently constructed +a remarkable telephonic instrument, which +reproduces speech and song in a quite exceptional and +simple way. It consists of a drum 15 centimètres in +diameter, covered with parchment at one end only. Six +small tin armatures, one centimètre in length and two +millimètres in width, are fixed in the centre of the parchment +in a circle six centimètres in diameter. Six +microscopic electro-magnets, whose distance from the +armatures can be regulated by a screw, are placed +opposite the armatures within a wooden circle. The +magnets are horseshoe, with branches 12 millimètres long +and 4 millimètres in diameter, including the coils, and the +magnetic core is 1½ millimètre thick. They are all in +connection, and act simultaneously under the sole influence +of the battery current. The sender is the same +as that of M. Ader described before. With this instrument +speech may be heard at a distance of six or seven<span class="pagenum" id="Page_358">358</span> +yards, and songs are much more distinctly heard than in +the singing condenser. Owing to the simplicity of the +arrangement, the instrument is not costly.</p> + +<p>The extraordinary effects of this telephone are due to +the small size of the electro-magnets, which, as we believe, +produce much more rapid magnetic effects than those of +larger size. M. Ader has also made a small ordinary +telephone based on this principle, of which the sounds +are much stronger than in others.</p> + +<p><i>Modification of Bell Telephone.</i>—Mr. Gower has recently +made a new system of telephone without a battery, +which not only reproduces speech loudly enough to be +heard at the distance of eight or nine yards from the instrument, +but will also transmit it when the speaker is at +a moderate distance from the sending instrument. In +this latter case, indeed, the receiving telephone must be +brought close to the ear. Although this double problem +had already been solved by the use of telephones with +microphonic senders, the results furnished by the instruments +in question are still more curious, since they are +obtained without batteries, and are even more distinct.</p> + +<p>In this new system, which is only an improvement on +Bell’s square model, the horseshoe magnet is of a +peculiar form, which renders it more powerful. It is +formed of a kind of half-circle of magnetised steel, with +its two ends turned back, so as to form a diameter of the +circle, only this diameter is divided in the centre: so that +the two poles of the magnet are placed one before the +other, as in Faraday’s electro-magnet. The poles are +tipped with iron, terminating in front in two thin iron +plates, on which are placed the electro-magnetic coils, +which are oblong, and constitute the magnetic core. +The diaphragm, thicker than the ordinary diaphragms, is +of tin, and is fixed firmly to the edges of the circular box<span class="pagenum" id="Page_359">359</span> +which encloses the whole, and which forms a kind of +sounding-box. The box is made of copper, and the +diaphragm is so firmly fastened to it as to become +homogeneous with it, and to give out a sound when the +box is touched, which is not the case in ordinary telephones. +This is one of the conditions which make the +instrument a better conductor of sound. The magnet is +also much more powerful. It is magnetised by a current +from a powerful Gramme machine, which acts upon it for +almost twenty minutes. The instrument has, strictly +speaking, no mouthpiece: the lid of the box which +supports the diaphragm, and is separated from it by a +space of two millimètres, has merely a hole bored in it +above the centre of the diaphragm, and into this hole +either a tin trumpet, 50 centimètres in length, is screwed, +when the instrument is required to reproduce or transmit +speech to a distance, or an acoustic tube when it is to +be used like an ordinary telephone. The remarkable +part of the system is that the instrument can itself give +a very loud call by only breathing into it instead of +speaking.</p> + +<p>For this purpose a small oblong opening is made in +the diaphragm at a half diameter from its centre, and +behind this the reed of an harmonium is applied to a +square copper plate fixed on the diaphragm itself. On +using the bellows the expelled air passes through this +little hole, and, on reaching the reed, sets it in vibration, +and produces a sound of which the acuteness +depends on the conditions of the vibrating plate. This +addition to the diaphragm in no way alters its properties +in the reproduction of speech, so that, after using the +bellows, conversation may begin, and the receiving telephone +repeats what is said after emitting a sound somewhat +resembling the note of a bugle. The instrument<span class="pagenum" id="Page_360">360</span> +is then provided with the speaking tube of which we have +spoken.</p> + +<p>Nothing can be more remarkable than this power of +listening to conversation while seated in an armchair +six or seven yards from the instrument, nor is it necessary +to move in order to reply. The correspondent, indeed, +must be close to the acoustic tube in order to speak and +listen, and he must speak rather loud in order to be +heard at any distance from the other station. But the +listener receives the sounds so amplified that it might be +supposed that a giant was speaking, and conversation +held in a low tone may even be distinguished. These +results are really extraordinary, and even to those +familiar with such effects this incessant progress is surprising.</p> + +<p>These results may be ascribed to the following +<span class="locked">causes:—</span></p> + +<p>1. First, that the conditions of the magnet are better +than those of ordinary instruments.</p> + +<p>2. That the diaphragm is also thicker, larger, and +better stretched.</p> + +<p>3. That the box is of metal, and calculated to act as +a sounding-box.</p> + +<p>4. The speaking trumpet magnifies the sounds.</p> + +<p>5. The acoustic tubes concentrate the sound waves +on the centre of the diaphragm.</p> + +<p><i>Note on some fresh Experiments with Telephones +without any Diaphragm.</i></p> + +<p>In a paper published March 4, 1878, I made some +suggestions on the theory of the sounds produced in the +telephone, and on the contradictory assertions of +physicists as to the transmission of speech by ordinary<span class="pagenum" id="Page_361">361</span> +telephones when devoid of diaphragm. These remarks +induced M. Ader to undertake some experiments which +not only demonstrate the truth of my opinion, but bring +to light some fresh facts which may be of great importance +to acoustic science.</p> + +<p>M. Ader has in fact not only succeeded in making a +telephone without a diaphragm speak, but he has made +it speak more loudly and with less alteration of the voice +than we find to be the case with a small model of the +ordinary telephone. No one, therefore, can now maintain +that the sounds produced by the magnetic cores are +so faint that they cannot be taken into account among +the effects produced, and that it is at any rate impossible +for them to reproduce articulate sounds.</p> + +<p>To obtain this result, M. Ader reduced the size of the +magnetic core to that of a simple iron wire, one millimètre +in diameter, and he fastened it by one of its ends +to a small wooden board. Under these conditions, it +was enough to fasten a small helix of fine wire on this +iron wire, and to apply the board to the ear in order to +hear speech distinctly, with the aid of a microphonic +speaker actuated by a voltaic current. But the range +of sound was considerably increased if a mass of metal +was applied to the free end of the iron wire: in this case +it was possible to hear when the wooden board was +removed to a distance of ten or fifteen centimètres from +the ear.</p> + +<p>If the wire is in contact with masses of metal at each +end, the effect is further increased; but the two masses +must not be in metallic communication with each other, +and must be to some extent insulated by a more or less +elastic medium. If the metallic masses are soldered to +the wire, the effects are still greater.</p> + +<p>M. Ader was also able to reproduce speech by using<span class="pagenum" id="Page_362">362</span> +a simple coil without a magnetic core, but in this case +the spirals must be open, and not pressed together. If they +are steeped in gum, no sound is heard, but speech will +become instantly audible if a wire or a magnetised needle +is inserted in the coil, or even if a second metallic helix is +placed in the circuit: always provided that one of the +ends of these magnetic organs rests upon, or is fastened +to, the board on which the coil is fixed.</p> + +<p>M. Ader has likewise obtained a very distinct reproduction +of speech at a distance of two or three yards from +the instrument by inserting between the two stretched +membranes of two tambourines a bent wire which acts as +a spring and passes through an electro-magnetic coil. +Under these conditions, magnetisation of the wire in a +greater or less degree affects its elasticity and causes +vibrations which are magnified by the membranes, and +transmitted sounds are reproduced with intensity. Unfortunately +articulate speech is less distinct with this +system than with the one I described before.</p> + +<p>M. Ader has often had occasion to make one curious +remark, namely, that the <em>timbre</em> of the voice and its high +or low key varies with the degree of tension given to the +wire; but if the fundamental note of the wire is deadened +by pressing it between the fingers, the sounds reproduced +then become dull and monotonous. They are also +somewhat fainter.</p> + +<p>Signor Carlo Resio has also observed that in a telephone +sender the variations of intensity in the current +correspond with the vibrations caused by speech, and +these are reproduced by corresponding variations in a +liquid column, which may thus act as a telephone +receiver, and consequently may reproduce speech without +any electro-magnetic organ, as in a microphone +speaker. Under these conditions, however, a layer of<span class="pagenum" id="Page_363">363</span> +water is inserted between the platinum electrodes and +the surrounding air, and consequently this liquid layer +must be put in vibration under the influence of varying +intensities of current.</p> + +<p>Mr. Edison has also now made a practical application +of the chemical telephone we have mentioned before. +The trials made with it have been very satisfactory, +showing that sounds transmitted in this way can be heard +in a large room.</p> + +<p class="p4 center vspace wspace"> +<span class="small">PRINTED BY<br> +SPOTTISWOODE AND CO., NEW-STREET SQUARE<br> +LONDON</span> +</p> + +<div class="chapter footnotes"> +<h2 class="nobreak" id="FOOTNOTES">FOOTNOTES</h2> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_1" href="#FNanchor_1" class="label">1</a> Mr. Gray, in an article inserted in the <cite>Telegrapher</cite> of October +7, 1876, enters into full details of this mode of transmitting sounds +by the tissues of the human body, and he gives the following as the +conditions in which it must be placed to obtain a favourable result: +1. The electricity must be of a high tension, in order to have an +effect perceptible to the ear.</p> + +<p>2. The substance employed to touch the metallic plate must be +soft, flexible, and a good conductor, up to the point of contact: it +must then interpose a slight resistance, neither too great nor too +small.</p> + +<p>3. The disk and the hand, or any other tissue, must not only be +in contact, but the contact must result from rubbing or gliding over +the surface.</p> + +<p>4. The parts in contact must be dry, so as to maintain the required +degree of resistance.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_2" href="#FNanchor_2" class="label">2</a> He cites the following names in his account of electric telephony:—Page, +Marrian, Beatson, Gassiot, De la Rive, Matteucci, +Guillemin, Wertheim, Wartmann, Janniar, Joule, Laborde, Legat, +Reiss, Poggendorf, Du Moncel, Delezenne, Gore, &c. Vide Mr. +Bell’s paper, in the <cite>Journal of the Society of Telegraphic Engineers</cite> +in London, vol. vi. pp. 390, 391.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_3" href="#FNanchor_3" class="label">3</a> This statement is disputed by Mr. Elisha Gray, owing, as we +shall see, to a misunderstanding as to the word <em>undulatory</em> current.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_4" href="#FNanchor_4" class="label">4</a> <cite>Elisha Gray.</cite> Eng. Pat. Spec. No. 2646, Aug. 1874.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_5" href="#FNanchor_5" class="label">5</a> This property has long been known, but not applied. In 1856, +in the second edition of my <cite lang="fr">Exposé des applications d’Electricité</cite>, I +pointed them out in speaking of the contact-breakers. I also spoke +of them in a paper on electro-magnets (published in the <cite lang="fr">Annales +télégraphiques</cite>, 1865), and in several articles laid before the <cite lang="fr">Académie +des Sciences</cite> in 1872 and 1875 on the conductivity of filings and +conducting powders. M. Clérac, in 1865, also used them to obtain +variable resistances.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_6" href="#FNanchor_6" class="label">6</a> In 1865 I was able to verify this observation when tightening +the spirals of an electro-magnet on a naked wire. The greater the +number of spirals under pressure, the more definite were the differences +of resistance in the magnetising helix.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_7" href="#FNanchor_7" class="label">7</a> M. Hellesen communicated the plan of his instrument to me +on May 3, 1878, and his experiments were made in Copenhagen +three weeks earlier.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_8" href="#FNanchor_8" class="label">8</a> M. M. J. Page had already noticed that if a telephone is placed +in the circuit of the primary helix of an induction coil, while the +secondary helix of this instrument is placed in the circuit of one of +M. Lippmann’s capillary electrometers, a movement of the mercurial +column of the electrometer takes place at each word, and this movement +is effected towards the capillary end of the tube, in whatever +direction the current is sent by the telephone. This is because the +mercury always tends to move more rapidly at its capillary end than +at the other extremity.</p> + +</div> + +<div class="footnote"> + +<p class="fn1"><a id="Footnote_9" href="#FNanchor_9" class="label">9</a> Mr. Edison, in a letter written November 25, 1877, writes +that he has made two telephones which act with copper diaphragms, +based on Arago’s effects of magnetism by rotation. He ascertained +that a copper diaphragm might replace the iron plate, if its thickness +did not exceed 1/32 of an inch. The effect produced is slight when +the copper diaphragm is placed between two corresponding instruments; +but when the sender only is furnished with the copper +diaphragm, and the receiver is arranged as usual, communication +becomes easy.</p> + +<p>Mr. Preece repeated these experiments, but he only obtained +very slight and indistinct effects: he consequently believes that they +are of no practical use, although very interesting in theory.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_10" href="#FNanchor_10" class="label">10</a> Mr. Bell had previously made a like experiment, which suggested +to him that molecular vibrations had as much to do with the +action of the telephone as mechanical vibrations.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_11" href="#FNanchor_11" class="label">11</a> M. Bosscha, who has published in the <cite lang="fr">Archives néerlandaises</cite> +an interesting paper on the intensity of electric currents in the telephone, +says that the minimum intensity of currents necessary to +produce a sound in a telephone by the vibration of its diaphragm +may be less than 100/1000 of a Daniell element, and the displacement +of the centre of the diaphragm would then be invisible. He was +unable to measure exactly the range of movements produced in the +diaphragm by the influence of the voice, but he believes it to be +less than the thousandth part of a millimètre; and from this it follows +that, for a sound of 880 vibrations, the intensity of the induced currents +developed would be 0·0000792 of the unit of electro-magnetic +intensity.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_12" href="#FNanchor_12" class="label">12</a> Mr. Warwick describes his experiments as follows: ‘The magnets +employed were nearly of the usual size, 1½ inch in diameter, +and nearly eight times as long. At first I employed iron disks, but +I found them to be unnecessary. When I had discarded them, I +tried several substances: first a thin disk of iron, which answered +perfectly both for sender and receiver. A disk of sheet iron, +about ⅒ of an inch in thickness, did not act so well, but all that +was said was quite understood. In making experiments with the +disks, I simply placed them above the instrument, without fixing +them in any way: the wooden cover and the conical cavity were +also laid aside, because the transmission and reception could be +effected as well without them. This part of the instrument seems to +be superfluous, since, when the disk is simply placed level to the ear, +the sound seems to be increased by being brought nearer. Although +iron acts better than anything, it appears that iron disks are not +absolutely necessary, and that diamagnetic substances also act +perfectly. I wished that my assistant, who was at some distance, +and could not hear any direct sound, should continue his calculations. +I took away the iron disk and placed across the instrument a wide +iron bar, an inch thick. On applying my ear to it, I could hear +every sound distinctly, but somewhat more faintly. A piece of +copper, three inches square, was substituted for it: although the +sound was still distinct, it was fainter than before. Thick pieces of +lead, zinc, and steel were alternately tried. The steel acted in +almost the same way as the iron, and, as in the other cases, each +word was heard faintly but distinctly. Some of these metals are +diamagnetic, and yet the action took place. Some non-metallic +substances were next tried; first a piece of window-glass, which +acted very well. The action was faint with a piece of a wooden +match-box; but on using pieces of gradually increasing thickness +the sound was sensibly increased, and with a piece of solid wood, +1½ inch in thickness, the sound was perfectly distinct. I next +replaced it by an empty wooden box, which acted very well. A +piece of cork, ½ inch thick, acted, but somewhat faintly. A block +of razor-stone, 2 inches thick, was placed upon the instrument; and, +on applying the ear to it, it was quite easy to follow the speaker. +I then tried to hear without the insertion of any substance, and, on +applying my ear quite close to the coil and magnet, I heard a faint +sound, and on listening attentively I understood all that was said. +In all these experiments the sounds were perceived, but the sounds +transmitted or attempted did not act precisely alike. The sound of +a tuning-fork, placed on the iron disk itself or on the case of the +instrument, was clearly heard: thin iron disks were more effective +for articulate speech. With other substances, stone, solid wood, glass, +zinc, &c., the sound of the tuning-fork was heard, whether it rested +upon them, or the vibrating fork was held above them. These substances +were not adapted for transmitting the sound of the voice. +These were all laid aside, and the sounding instrument was held +directly above the pole of the magnet: the sound was clearly heard, +although there was nothing but air between the end of the magnet +and the tuning-fork. The sound was perhaps less intense when the +tuning-fork was held directly above the pole, than when it was at +the end of the magnet. I next tried if my voice could be heard +with this arrangement. The result was rather doubtful, but I think +that some action must have taken place, for the tuning-fork was +heard when it was simply vibrated near the pole. The effect of the +voice can only have differed in the degree of intensity: it was too +faint to be heard at the other extremity. I repeated these effects; +I assured myself of them, and I succeeded in transmitting sounds +distinctly on the pole without a disk, and, on the other hand, by +applying my ear to the instrument, I was able to hear distinctly all +that was said, although there was no disk.’</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_13" href="#FNanchor_13" class="label">13</a> These are his own words: ‘The articulation produced from the +instrument was remarkably clear, but its great defect consisted in +the fact that it could not be used as a sending instrument, and thus +two telephones were required at each station, one for transmitting +and one for receiving spoken messages.’</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_14" href="#FNanchor_14" class="label">14</a> These carbons are made by heating, in a temperature gradually +raised to white heat, fragments of deal of a close fibre, which is +enclosed in an iron tube or box hermetically sealed.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_15" href="#FNanchor_15" class="label">15</a> Mr. Willoughby Smith varied this experiment by placing a +packet of silk threads coated with copper on the disconnected ends +of the circuit, which were arranged at right angles with each other. +Under these conditions the instrument became so sensitive, that the +current of air produced by a lamp placed above the system, caused +a decided crackling noise in the telephone.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_16" href="#FNanchor_16" class="label">16</a> Mr. Hughes observes on this subject that carbon is a valuable +material for such purposes, since it does not oxidise, and its +effects are greater when combined with mercury. He takes the +prepared charcoal used by artists, brings it to a white heat, and +suddenly plunges it in a bath of mercury, of which the globules instantly +penetrate the pores of charcoal, and may be said to metallise +it. He also tried charcoal coated with a deposit of platinum, or +impregnated with chloride of platinum, but this was not more successful +than the former method. If the charcoal of fir-wood is +brought to a white heat in an iron tube, containing tin and zinc, or +any other metal which readily evaporates, it is metallised, and is +adapted for use if the metal is subdivided in the pores of charcoal +and not combined with it. When iron is introduced into carbon +in this way it is one of the most effective metals. The charcoal of +fir-wood, in itself a bad conductor, may thus acquire great conducting +power.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_17" href="#FNanchor_17" class="label">17</a> Mr. Hughes remarks that the vibrations which affect the microphone, +even in speaking at a distance from the instrument, do not +proceed from the direct action of the sound waves on the contacts of +the microphone, but from the molecular vibrations produced by it +on the board which serves to support the instrument; he shows, in +fact, that the intensity of sounds produced by the microphone is in +proportion to the size of the surface of this board, and when the +sending microphone is enclosed in a cylindrical case, its sensitiveness +is not much diminished if the surface of the box enclosing the whole +is sufficiently large. From this point of view he has sought to increase +the sensitiveness of his instruments by fixing the frame on +which the moveable parts of the sender and receiver revolve on a +spring plate.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_18" href="#FNanchor_18" class="label">18</a> Helmholtz’s resonator is based upon the principle that a volume +of air contained in an open vase emits a certain note when +placed in vibration, and that the height of the note depends on the +size of the vase and of its opening. Helmholtz makes use of a globe +with a large opening on one side and a small one on the other, +and the small one is applied to the ear. If a series of musical notes +take place in the air, the one which is in harmony with the fundamental +note of the globe is intensified, and can be distinguished +from the rest. The same effect takes place when, on singing to +a piano accompaniment, some strings are heard to vibrate more +strongly than others, namely, those which vibrate in unison with +the sounds emitted. The resonators are made in various ways; +those most generally used are cases of different lengths which also +serve as sounding-boxes.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_19" href="#FNanchor_19" class="label">19</a> I give the text of M. Cros’ sealed paper, opened by his +request, at the Académie des Sciences, December 3, 1877:—‘Speaking +generally, my process consists in obtaining traces of the +movement to and fro of a vibrating membrane, and in using this +tracing to reproduce the same movements, with their intrinsic +relations of duration and intensity, either on the same membrane +or on one adapted to give out the sounds which result from this +series of movements.</p> + +<p>‘It is therefore necessary that an extremely delicate tracing, such +as may be obtained by passing a needle over a surface blackened +by fire, should be transformed into a tracing, capable of sufficient +resistance to guide an index which will transmit its movements to +the membrane of sound.</p> + +<p>‘A light index is fastened to the centre of a vibrating membrane; +it terminates in a point (a metallic wire or tip of a feather) which +rests on a surface which has been blackened by fire. This surface +forms part of a disk, to which the double action of rotation and +rectilinear progression has been given. If the membrane is at +rest, the point will trace a simple spiral; if the membrane vibrates, +there will be undulations in the spiral, and these undulations will +represent the precise movements of the membrane in their duration +and intensity.</p> + +<p>‘By a well-known photographic process a transparent tracing of +the undulations of the spiral can be represented by a line of similar +dimensions on some resisting substance, tempered steel for +example.</p> + +<p>‘When this is done, this resisting surface is placed in a turning +machine which causes it to revolve and advance with a velocity and +motion similar to those by which the registering surface was +actuated. A metallic point if the tracing is concave, or a grooved +index if it is in relief, is kept upon the tracing by a spring, and the +index which supports this point is connected with the centre of the +membrane which produces the sounds. Under these conditions, +the membrane will be actuated not by the vibrating air, but by the +tracing which guides the index, and the impulses will be precisely +similar in duration and intensity to those to which the registering +membrane was subjected.</p> + +<p>‘The spiral tracing represents equal successions of time by +increasing or decreasing lengths. There is no inconvenience in +this, since the turns of the spiral are very close together, if only the +circumference of the turning circle is used; but then the central +surface is lost.</p> + +<p>‘In all cases the tracing of the helix on a cylinder is much +more satisfactory, and I am now trying to make this idea practicable.’</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_20" href="#FNanchor_20" class="label">20</a> Never make a contact between the stylus and the cylinder until +the latter is covered with the tinfoil. Do not begin to turn the +cylinder until assured that everything is in its place. Take care, +when the stylus returns to the point of departure, to bring the +mouthpiece forward. Always leave a margin of from five to ten +millimètres on the left and at the beginning of the sheet of tinfoil; +for if the stylus describes the curve on the extreme edge of the +cylinder, it may tear the sheet or come out of the groove. Be +careful not to detach the spring of the caoutchouc pad.</p> + +<p>To fix the tinfoil, apply varnish to the end with a paint-brush; +take this end between the finger and thumb of the left hand, with the +sticky part towards the cylinder; raise it with the right hand and +apply it quite smoothly to the cylinder; bring round the sticky end, +and join them firmly.</p> + +<p>To adjust the stylus and place it in the centre of the groove, +bring the cylinder to the right, so as to place the stylus opposite the +left extremity of the tinfoil; bring forward the cylinder gently and +by degrees, until the stylus touches the tinfoil with force enough to +imprint a mark. Observe if this mark is quite in the centre of the +groove (in order to do this, make a mark with the nail across the +cylinder), and if it is not, adjust the stylus to the right or left by means +of the little screw placed above the mouthpiece. The depth of the +impression made by the stylus should be ⅓ millimètre, just enough for +it to leave a slight tracing, whatever the range of vibrations may be.</p> + +<p>To reproduce the words, the winch must be turned with the +same velocity as when they were inscribed. The average velocity +should be about eighty turns a minute.</p> + +<p>In speaking, the lips must touch the mouthpiece, and deep +guttural sounds are better heard than those which are shrill. In +reproducing, the tightening screw must be loosened and brought in +front of the mouthpiece, the cylinder must be brought back to its +point of departure, the contact between the stylus and the foil must +be renewed, and the cylinder must again be turned in the same +direction as when the sentence was spoken.</p> + +<p>To increase the volume of reproduced sound, a tube of cardboard, +wood, or horn may be applied to the mouthpiece; it must be +of a conical form, and its lower end should be rather larger than +the opening of the mouthpiece.</p> + +<p>The stylus consists of a No. 9 needle, somewhat flattened on its +two sides by friction on an oiled stone. The caoutchouc pad which +connects the plate with the disk serves to weaken the vibrations of +the plate. If this pad should come off, heat the head of a small +nail, apply it to the wax which fastens the pad to the plate or to the +spring, so as to soften it; then press the caoutchouc lightly, until it +adheres to the place from which it was detached. The pads must +be renewed from time to time, as they lose their elasticity. Care must +be taken in replacing them not to injure the vibrating plate, either +by too strong a pressure or by grazing it with the instrument employed +to fix the pad.</p> + +<p>The first experiments should be with single words or very short +sentences, which can be extended as the ear becomes accustomed to +the instrument’s peculiar tone.</p> + +<p>The tone is varied by accelerating or slackening the rotatory +movement of the cylinder. The cries of animals may be imitated. +Instrumental music may be reproduced by placing a cardboard +tube before the mouthpiece. The airs should be played in rapid +time, since, when there is no system of clockwork, they will be +more perfectly reproduced than those which are played slowly.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_21" href="#FNanchor_21" class="label">21</a> We confess that we find it difficult to believe in this property +of the phonograph, from which we have only heard the harsh and +unpleasant voice of Punch.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_22" href="#FNanchor_22" class="label">22</a> The action of this pedal is effected by two little rockers, so +connected that the upper damper is lowered a little before the lower +damper is raised—a condition necessary to produce the quivering +motion of the plate which furnishes the rolling <i>r</i>.</p> + +</div> + +<div class="footnote"> + +<p class="fn2"><a id="Footnote_23" href="#FNanchor_23" class="label">23</a> The arrangement of this part of the instrument is remarkable +in this particular, that in the case of certain letters the air is ejected +with more or less force through the pipe <span class="allsmcap">I</span>, while in the case of +other letters the air is drawn into the same tube. Since I was +unable to see the internal arrangement of these cavities, I can only +give an imperfect account of the mechanism at work.</p> + +</div> +</div> + +<div class="chapter transnote"> +<h2 class="nobreak" id="Transcribers_Notes">Transcriber’s Notes</h2> + +<p>Punctuation, hyphenation, and spelling were made +consistent when a predominant preference was found +in the original book; otherwise they were not changed.</p> + +<p>Simple typographical errors were corrected; unbalanced +quotation marks were remedied when the change was +obvious, and otherwise left unbalanced.</p> + +<p>Illustrations in this eBook have been positioned +between paragraphs and outside quotations.</p> + +<p>Footnotes, originally at the bottoms of the pages that referenced them, +have been collected, sequentially renumbered, and placed near the end of +the book.</p> + +<p>The Table of Contents is not well-coordinated +with the actual text. The Transcriber has not +added missing entries, but has attempted to +correct page number discrepancies.</p> + +<p>Several diagrams use labels with prime marks, but +the accompanying explanations do not +always include the prime marks. +</p> +</div> + +<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 75683 ***</div> +</body> +</html> + diff --git a/75683-h/images/cover.jpg b/75683-h/images/cover.jpg Binary files differnew file mode 100644 index 0000000..b2b7293 --- /dev/null +++ b/75683-h/images/cover.jpg diff --git a/75683-h/images/i_p012.jpg b/75683-h/images/i_p012.jpg Binary files differnew file mode 100644 index 0000000..4cc24ef --- /dev/null +++ b/75683-h/images/i_p012.jpg diff --git a/75683-h/images/i_p016.jpg b/75683-h/images/i_p016.jpg Binary files differnew file mode 100644 index 0000000..5be4648 --- /dev/null +++ b/75683-h/images/i_p016.jpg diff --git a/75683-h/images/i_p017.jpg b/75683-h/images/i_p017.jpg Binary files differnew file mode 100644 index 0000000..45a56ce --- /dev/null +++ b/75683-h/images/i_p017.jpg diff --git a/75683-h/images/i_p023.jpg b/75683-h/images/i_p023.jpg Binary files differnew file mode 100644 index 0000000..7bb4a73 --- /dev/null +++ b/75683-h/images/i_p023.jpg diff --git a/75683-h/images/i_p028.jpg b/75683-h/images/i_p028.jpg Binary files differnew file mode 100644 index 0000000..db64c6b --- /dev/null +++ b/75683-h/images/i_p028.jpg diff --git a/75683-h/images/i_p032.jpg b/75683-h/images/i_p032.jpg Binary files differnew file mode 100644 index 0000000..573005f --- /dev/null +++ b/75683-h/images/i_p032.jpg diff --git a/75683-h/images/i_p040.jpg b/75683-h/images/i_p040.jpg Binary files differnew file mode 100644 index 0000000..7cbe98c --- /dev/null +++ b/75683-h/images/i_p040.jpg diff --git a/75683-h/images/i_p041.jpg b/75683-h/images/i_p041.jpg Binary files differnew file mode 100644 index 0000000..c0fed3e --- /dev/null +++ b/75683-h/images/i_p041.jpg diff --git a/75683-h/images/i_p041b.jpg b/75683-h/images/i_p041b.jpg Binary files differnew file mode 100644 index 0000000..8f90f1a --- /dev/null +++ b/75683-h/images/i_p041b.jpg diff --git a/75683-h/images/i_p042.jpg b/75683-h/images/i_p042.jpg Binary files differnew file mode 100644 index 0000000..e652b57 --- /dev/null +++ b/75683-h/images/i_p042.jpg diff --git a/75683-h/images/i_p046.jpg b/75683-h/images/i_p046.jpg Binary files differnew file mode 100644 index 0000000..a05b80f --- /dev/null +++ b/75683-h/images/i_p046.jpg diff --git a/75683-h/images/i_p047.jpg b/75683-h/images/i_p047.jpg Binary files differnew file mode 100644 index 0000000..eb2238b --- /dev/null +++ b/75683-h/images/i_p047.jpg diff --git a/75683-h/images/i_p049.jpg b/75683-h/images/i_p049.jpg Binary files differnew file mode 100644 index 0000000..38ba6ed --- /dev/null +++ b/75683-h/images/i_p049.jpg diff --git a/75683-h/images/i_p050.jpg b/75683-h/images/i_p050.jpg Binary files differnew file mode 100644 index 0000000..dbdd9d9 --- /dev/null +++ b/75683-h/images/i_p050.jpg diff --git a/75683-h/images/i_p051.jpg b/75683-h/images/i_p051.jpg Binary files differnew file mode 100644 index 0000000..56d94e0 --- /dev/null +++ b/75683-h/images/i_p051.jpg diff --git a/75683-h/images/i_p053.jpg b/75683-h/images/i_p053.jpg Binary files differnew file mode 100644 index 0000000..f433594 --- /dev/null +++ b/75683-h/images/i_p053.jpg diff --git a/75683-h/images/i_p054.jpg b/75683-h/images/i_p054.jpg Binary files differnew file mode 100644 index 0000000..87f718b --- /dev/null +++ b/75683-h/images/i_p054.jpg diff --git a/75683-h/images/i_p055.jpg b/75683-h/images/i_p055.jpg Binary files differnew file mode 100644 index 0000000..1629cff --- /dev/null +++ b/75683-h/images/i_p055.jpg diff --git a/75683-h/images/i_p056.jpg b/75683-h/images/i_p056.jpg Binary files differnew file mode 100644 index 0000000..a016f9e --- /dev/null +++ b/75683-h/images/i_p056.jpg diff --git a/75683-h/images/i_p062.jpg b/75683-h/images/i_p062.jpg Binary files differnew file mode 100644 index 0000000..063f67b --- /dev/null +++ b/75683-h/images/i_p062.jpg diff --git a/75683-h/images/i_p072.jpg b/75683-h/images/i_p072.jpg Binary files differnew file mode 100644 index 0000000..1f042b1 --- /dev/null +++ b/75683-h/images/i_p072.jpg diff --git a/75683-h/images/i_p073.jpg b/75683-h/images/i_p073.jpg Binary files differnew file mode 100644 index 0000000..1a51fea --- /dev/null +++ b/75683-h/images/i_p073.jpg diff --git a/75683-h/images/i_p076.jpg b/75683-h/images/i_p076.jpg Binary files differnew file mode 100644 index 0000000..bd7fbb0 --- /dev/null +++ b/75683-h/images/i_p076.jpg diff --git a/75683-h/images/i_p077.jpg b/75683-h/images/i_p077.jpg Binary files differnew file mode 100644 index 0000000..36056b2 --- /dev/null +++ b/75683-h/images/i_p077.jpg diff --git a/75683-h/images/i_p081.jpg b/75683-h/images/i_p081.jpg Binary files differnew file mode 100644 index 0000000..46dca87 --- /dev/null +++ b/75683-h/images/i_p081.jpg diff --git a/75683-h/images/i_p082.jpg b/75683-h/images/i_p082.jpg Binary files differnew file mode 100644 index 0000000..842dffb --- /dev/null +++ b/75683-h/images/i_p082.jpg diff --git a/75683-h/images/i_p085.jpg b/75683-h/images/i_p085.jpg Binary files differnew file mode 100644 index 0000000..26ea5a4 --- /dev/null +++ b/75683-h/images/i_p085.jpg diff --git a/75683-h/images/i_p087.jpg b/75683-h/images/i_p087.jpg Binary files differnew file mode 100644 index 0000000..d8f2f50 --- /dev/null +++ b/75683-h/images/i_p087.jpg diff --git a/75683-h/images/i_p088.jpg b/75683-h/images/i_p088.jpg Binary files differnew file mode 100644 index 0000000..a80ccd6 --- /dev/null +++ b/75683-h/images/i_p088.jpg diff --git a/75683-h/images/i_p095.jpg b/75683-h/images/i_p095.jpg Binary files differnew file mode 100644 index 0000000..0b77b3b --- /dev/null +++ b/75683-h/images/i_p095.jpg diff --git a/75683-h/images/i_p096.jpg b/75683-h/images/i_p096.jpg Binary files differnew file mode 100644 index 0000000..e91a150 --- /dev/null +++ b/75683-h/images/i_p096.jpg diff --git a/75683-h/images/i_p098.jpg b/75683-h/images/i_p098.jpg Binary files differnew file mode 100644 index 0000000..7b380d4 --- /dev/null +++ b/75683-h/images/i_p098.jpg diff --git a/75683-h/images/i_p100.jpg b/75683-h/images/i_p100.jpg Binary files differnew file mode 100644 index 0000000..5f12d67 --- /dev/null +++ b/75683-h/images/i_p100.jpg diff --git a/75683-h/images/i_p111.jpg b/75683-h/images/i_p111.jpg Binary files differnew file mode 100644 index 0000000..f730d54 --- /dev/null +++ b/75683-h/images/i_p111.jpg diff --git a/75683-h/images/i_p117.jpg b/75683-h/images/i_p117.jpg Binary files differnew file mode 100644 index 0000000..14bea1e --- /dev/null +++ b/75683-h/images/i_p117.jpg diff --git a/75683-h/images/i_p122.jpg b/75683-h/images/i_p122.jpg Binary files differnew file mode 100644 index 0000000..5ae447c --- /dev/null +++ b/75683-h/images/i_p122.jpg diff --git a/75683-h/images/i_p127.jpg b/75683-h/images/i_p127.jpg Binary files differnew file mode 100644 index 0000000..780bd47 --- /dev/null +++ b/75683-h/images/i_p127.jpg diff --git a/75683-h/images/i_p127b.jpg b/75683-h/images/i_p127b.jpg Binary files differnew file mode 100644 index 0000000..2770417 --- /dev/null +++ b/75683-h/images/i_p127b.jpg diff --git a/75683-h/images/i_p188.jpg b/75683-h/images/i_p188.jpg Binary files differnew file mode 100644 index 0000000..7e22d29 --- /dev/null +++ b/75683-h/images/i_p188.jpg diff --git a/75683-h/images/i_p190.jpg b/75683-h/images/i_p190.jpg Binary files differnew file mode 100644 index 0000000..17793f7 --- /dev/null +++ b/75683-h/images/i_p190.jpg diff --git a/75683-h/images/i_p192.jpg b/75683-h/images/i_p192.jpg Binary files differnew file mode 100644 index 0000000..fd0afbb --- /dev/null +++ b/75683-h/images/i_p192.jpg diff --git a/75683-h/images/i_p193.jpg b/75683-h/images/i_p193.jpg Binary files differnew file mode 100644 index 0000000..9a228ea --- /dev/null +++ b/75683-h/images/i_p193.jpg diff --git a/75683-h/images/i_p197.jpg b/75683-h/images/i_p197.jpg Binary files differnew file mode 100644 index 0000000..7b87088 --- /dev/null +++ b/75683-h/images/i_p197.jpg diff --git a/75683-h/images/i_p197b.jpg b/75683-h/images/i_p197b.jpg Binary files differnew file mode 100644 index 0000000..d9fe9bb --- /dev/null +++ b/75683-h/images/i_p197b.jpg diff --git a/75683-h/images/i_p202.jpg b/75683-h/images/i_p202.jpg Binary files differnew file mode 100644 index 0000000..c440cf7 --- /dev/null +++ b/75683-h/images/i_p202.jpg diff --git a/75683-h/images/i_p208.jpg b/75683-h/images/i_p208.jpg Binary files differnew file mode 100644 index 0000000..646749d --- /dev/null +++ b/75683-h/images/i_p208.jpg diff --git a/75683-h/images/i_p209.jpg b/75683-h/images/i_p209.jpg Binary files differnew file mode 100644 index 0000000..66e3176 --- /dev/null +++ b/75683-h/images/i_p209.jpg diff --git a/75683-h/images/i_p210.jpg b/75683-h/images/i_p210.jpg Binary files differnew file mode 100644 index 0000000..11187cb --- /dev/null +++ b/75683-h/images/i_p210.jpg diff --git a/75683-h/images/i_p213.jpg b/75683-h/images/i_p213.jpg Binary files differnew file mode 100644 index 0000000..c10185e --- /dev/null +++ b/75683-h/images/i_p213.jpg diff --git a/75683-h/images/i_p221.jpg b/75683-h/images/i_p221.jpg Binary files differnew file mode 100644 index 0000000..ddbf73f --- /dev/null +++ b/75683-h/images/i_p221.jpg diff --git a/75683-h/images/i_p233.jpg b/75683-h/images/i_p233.jpg Binary files differnew file mode 100644 index 0000000..1c6688e --- /dev/null +++ b/75683-h/images/i_p233.jpg diff --git a/75683-h/images/i_p235.jpg b/75683-h/images/i_p235.jpg Binary files differnew file mode 100644 index 0000000..49d6925 --- /dev/null +++ b/75683-h/images/i_p235.jpg diff --git a/75683-h/images/i_p253.jpg b/75683-h/images/i_p253.jpg Binary files differnew file mode 100644 index 0000000..d06f61a --- /dev/null +++ b/75683-h/images/i_p253.jpg diff --git a/75683-h/images/i_p255.jpg b/75683-h/images/i_p255.jpg Binary files differnew file mode 100644 index 0000000..51358dc --- /dev/null +++ b/75683-h/images/i_p255.jpg diff --git a/75683-h/images/i_p258.jpg b/75683-h/images/i_p258.jpg Binary files differnew file mode 100644 index 0000000..4003649 --- /dev/null +++ b/75683-h/images/i_p258.jpg diff --git a/75683-h/images/i_p262.jpg b/75683-h/images/i_p262.jpg Binary files differnew file mode 100644 index 0000000..4bf39d6 --- /dev/null +++ b/75683-h/images/i_p262.jpg diff --git a/75683-h/images/i_p264.jpg b/75683-h/images/i_p264.jpg Binary files differnew file mode 100644 index 0000000..cf24ac0 --- /dev/null +++ b/75683-h/images/i_p264.jpg diff --git a/75683-h/images/i_p264r.jpg b/75683-h/images/i_p264r.jpg Binary files differnew file mode 100644 index 0000000..f8e01b3 --- /dev/null +++ b/75683-h/images/i_p264r.jpg diff --git a/75683-h/images/i_p277.jpg b/75683-h/images/i_p277.jpg Binary files differnew file mode 100644 index 0000000..9608182 --- /dev/null +++ b/75683-h/images/i_p277.jpg diff --git a/75683-h/images/i_p278.jpg b/75683-h/images/i_p278.jpg Binary files differnew file mode 100644 index 0000000..15b26b4 --- /dev/null +++ b/75683-h/images/i_p278.jpg diff --git a/75683-h/images/i_p282.jpg b/75683-h/images/i_p282.jpg Binary files differnew file mode 100644 index 0000000..c1b9e06 --- /dev/null +++ b/75683-h/images/i_p282.jpg diff --git a/75683-h/images/i_p283.jpg b/75683-h/images/i_p283.jpg Binary files differnew file mode 100644 index 0000000..182ac2a --- /dev/null +++ b/75683-h/images/i_p283.jpg diff --git a/75683-h/images/i_p286.jpg b/75683-h/images/i_p286.jpg Binary files differnew file mode 100644 index 0000000..a44896f --- /dev/null +++ b/75683-h/images/i_p286.jpg diff --git a/75683-h/images/i_p288.jpg b/75683-h/images/i_p288.jpg Binary files differnew file mode 100644 index 0000000..f899598 --- /dev/null +++ b/75683-h/images/i_p288.jpg diff --git a/75683-h/images/i_p291.jpg b/75683-h/images/i_p291.jpg Binary files differnew file mode 100644 index 0000000..5f4a97d --- /dev/null +++ b/75683-h/images/i_p291.jpg diff --git a/75683-h/images/i_p314.jpg b/75683-h/images/i_p314.jpg Binary files differnew file mode 100644 index 0000000..90a0d5d --- /dev/null +++ b/75683-h/images/i_p314.jpg diff --git a/75683-h/images/i_p316.jpg b/75683-h/images/i_p316.jpg Binary files differnew file mode 100644 index 0000000..2074497 --- /dev/null +++ b/75683-h/images/i_p316.jpg diff --git a/75683-h/images/i_p318.jpg b/75683-h/images/i_p318.jpg Binary files differnew file mode 100644 index 0000000..443c602 --- /dev/null +++ b/75683-h/images/i_p318.jpg diff --git a/75683-h/images/i_p323.jpg b/75683-h/images/i_p323.jpg Binary files differnew file mode 100644 index 0000000..e400971 --- /dev/null +++ b/75683-h/images/i_p323.jpg diff --git a/75683-h/images/i_p325.jpg b/75683-h/images/i_p325.jpg Binary files differnew file mode 100644 index 0000000..fb73f2b --- /dev/null +++ b/75683-h/images/i_p325.jpg diff --git a/75683-h/images/i_p330.jpg b/75683-h/images/i_p330.jpg Binary files differnew file mode 100644 index 0000000..37bbdef --- /dev/null +++ b/75683-h/images/i_p330.jpg diff --git a/75683-h/images/i_p332.jpg b/75683-h/images/i_p332.jpg Binary files differnew file mode 100644 index 0000000..a9bd8e3 --- /dev/null +++ b/75683-h/images/i_p332.jpg diff --git a/75683-h/images/i_p345.jpg b/75683-h/images/i_p345.jpg Binary files differnew file mode 100644 index 0000000..ec34f27 --- /dev/null +++ b/75683-h/images/i_p345.jpg diff --git a/75683-h/images/i_p347.jpg b/75683-h/images/i_p347.jpg Binary files differnew file mode 100644 index 0000000..b2a4d26 --- /dev/null +++ b/75683-h/images/i_p347.jpg |
