808 



Popular Science Monthly 



Under 



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DETAIL OF 



MICROPHONIC 



TRANSMITTER 



primarily depended upon to guide the 

 submarine on its deadly errand, tele- 

 phones are connected with the micro- 

 phones, to be used when the occasion 

 arises. With their aid the commander 

 learns a new language. He realizes the 

 meaning of strange grindings, hums, 

 moans, blows, rnur- 

 murs and vibrations 

 — the many tongues 

 of the sea. If we but 

 knew it the water of 

 the ocean is a veri- 

 table Babel; it is a 

 great reservoir of 

 sound, the recipient 

 of ten thousand differ- 

 ent vibrations, rang- 

 ing from the grinding 

 of pebbles to the 

 pounding of steam- 

 ship engines. Just as a 

 woodsman learns the 

 meaning of the weird 

 soughing of wind in 

 tree tops, the "woof" 

 of a bear, the patter 

 of deer's feet and the 

 call of quail, so a 

 submarine comman- 

 der can distinguish 

 one underwater sound 

 from another and in- 

 terpret it correctly. 

 A tramp steamer can 

 be microphonically 

 distinguished from a 

 Mauretania, a tor- 

 pedo-boat from a 

 superdreadnought, 

 and above all a sub- 

 surface craft from a 

 surface craft. Thus 

 the character of an 

 unseen ship miles away can be ascer- 

 tained. 



But apart from listening to passmg 

 ships, the telephones will be required to 

 receive messages from an admiral on a 

 battleship live miles away. Both war- 

 ships and merchantmen are equipped 

 with submarine signaling devices — 

 devices which send forth either bell 

 sounds or rhythmic vibrations. It is 

 easy to see how useful they can be made 

 to telegraph orders to a submarine under 

 water five miles or more away. 



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MAGNETS 



BATTERY 



MAIN 

 BATTERY 



A diagram showing the Chandler sys- 

 tem of converting sounds heard through 

 a microphone into visible signals 



Water Echoes and How They 

 Are A pplied 

 In the foregoing account of my inven- 

 tion I have assumed that the vessel to 

 be attacked with the aid of the micro- 

 phonic steering-indicator is in motion — 

 that its engines are giving audible 

 sounds and that its 

 propellers are churn- 

 ing up water noisily. 

 But suppose the vessel 

 to be attacked is at 

 anchor — what then ? 

 Is not the submarine 

 commander helpless? 

 The difficulty is 

 easily overcome if we 

 can make the sub- 

 marine produce a 

 characteristic sound 

 and if we can have 

 that sound echoed 

 back from the ship to 

 be sunk and picked 

 up by the submarine's 

 own microphones. 

 Fortunately Professor 

 Fessenden has pro- 

 vided an instrument 

 ideally suited for the 

 purpose. Called an 

 oscillator, it may be 

 regarded as a kind of 

 underwater klaxon 

 norn, the diaphragm 

 of which is electrically 

 vibrated to emit a 

 characteristic bleat. 

 By means of a switch, 

 located near the hand 

 of the submarine com- 

 mander, the oscillator 

 can be turned on or 

 off. 



The oscillator will be of use not only to 

 locate a ship at rest but to save the 

 submarine in a nerve-racking emergency. 

 Imagine the commander of a U-boat 

 bent on the destruction of a ship enter- 

 ing a harbor and traveling along at the 

 surface with only his periscope exposed. 

 A fast armed motorboat looms up — a 

 type of craft which has proved to be 

 a most formidable enemy. The sub- 

 marine must act quickly. There is but 

 one course— to sink quickly. Valves are 

 opened and tanks filled. The craft 



