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
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