714 



Popular Science Monthly 



AUOHOL 



StCIION 



fELT-COV[R[B WHEtL 



WIS CUCniOMAGNfllC CtUICH IS f«STW- 

 fD 10 HOIOR SHAfI WHEN KOBSt KtV IS 

 Cf WiiSSfO, ClUHH IS MAGNilirtO IM WE 

 (OIIS) AND J!RK5 TH[ REVOLVINIj DISC 

 «fR A6MNSI IIS [AC! DISC mtREUPON 

 DEWIVIS AIONO WITH CLUKH AND HOIOl!, 

 CAUSING 1H( FECI WHEEUO TURN AND RUB 

 lHE51E£l5IHP,(ilVIN()0EEARESUIIANI 

 SOUND. 



WIS EEfOROHACNETIC ClUICH IS SIAIION 

 ARY.WHfN MOKE KEY ISBtEfASEO, II 

 6EC0MES ENERGIZED AND JERKS R(- 

 VOLVING DISC AWAY FROM ClUICH, [L- 

 [CIROMAGNEI CAUSING DISC 10 HALT 

 A5RUPIIY. THUS 5IOPPIN6 SHORI IKE 

 EflT WHEEL AND IIS SOUND THIS MAHES 

 IHf MORSE SIGNA15 CLEAN CUT AND 

 CLEAR 



ICfURING m DKIV- 

 iNOlHELJCIIING 

 WHEEL Fm COVER- 

 ED RiM ON lAHER 

 RUBS IHE SIELL 

 STRIP 



The Bcrger 

 apparatus 

 showing its 

 operation 

 from the 

 time that the 

 Morse key is 

 depressed 

 until the 

 vibrations 

 are sent out 



together. Since all sounds come to the 

 listener alike, it is obviously impossible 

 sometimes for him to tell whether he is 

 listening to a bell or to some strange 

 noise of the sea. 



Mr. Bcrger's sul^marinc signaling 

 device, however, has the one great 

 atU'antage that sounds sent out into the 

 water can be mack- to ha\-e an>' duration 

 desired. As long as the felt-rimmed 

 wheel keeps rubbing on the steel strij), a 

 steady, sustained note is sent outwaril. 

 As is explained in the illustration 

 above, tlie rul)bing of the wheel against 

 the strip is under control of a teje- 

 graph-key, the sender operating this 

 just as he would one on an ordin,ir\- elec- 

 tric telegrai)h circuit. As the first illu.s- 

 ti.ilion on page 712 makes clear, these 



signals sent out into the water are picked up by 

 a microphone (delicate form of telephone 

 transmitter) mounted in a water-filled chamber 

 in the side of the receiving vessel. The listener 

 simpK' adjusts telephone-receivers to his ears 

 and hears signals just as he would 

 hear ordinary wireless telegraph mes- 

 sages. This sound-wa\e telegraph is 

 as truh' a wireless telegraph as the 

 kind using electric waves. 



Commander F. L. Sawyer, of the 

 rnitc-d States Xa\>', has proposed 

 that the Bcrger in\ention be 

 combined with ordinary 

 wireless telegraphy, the two 

 together forming an effec- 

 tive means of warning in 

 case of fog. The fact that 

 electric waves tra\'cl with 

 the speed of light (i86,cxx) 

 miles per second), or almost 

 instantaneously, and that 

 sound wa\-es in water travel 

 much more slowly (4,708 

 feet per second), is the basis 

 for the proposed methcxl. 

 The electric signals and the 

 sound-signals are sent out 

 simultaneously by the ap- 

 j)roaching vessels. Ths lis- 

 tener on either boat hears 

 the wireless signal instantly 

 and the sound-signal a few 

 seconds later (it having taken 

 that long to arrive) and 

 he can judge fairly well 

 how far apart the r\vo vessels 

 are — the number of sec'onds 

 in this inter\al multiplied b>- the speed of 

 sound in water gi\iiig the aiijiroximate 

 distance. If the time intervening between 

 receiving the two signals grows less and 

 le.ss the operators know that the two 

 vessels are approaching and may collide. 

 A code system, composed of different 

 letters of the alj'jhabct and indicating 

 whate\er course the \essels are pursuing, 

 is .ilso proposed. 



Professor R. A. Fessenden has in- 

 vented an underwater sound-signaling 

 machine somewhat like Mr. Herger's. 

 His contrivance, however, makes use of 

 an electromagnetic oscillator working on 

 one of the i>lates of a vessel's hull in 

 place of Herger's vibrating wire. Both 

 contrivances are elTective means of com- 

 municating \\iili >ul>nurgi(l subm.irines. 



