SUBMARINE SIGNALING BLAKE. 211 



water-immersed microphones of the usual type, but one would per- 

 haps not anticipate the possibility of using the oscillator as a re- 

 ceiver in view of the fact that the diaphragm is of solid steel and 

 weighs, with the copper tube and its attachments, considerably over 

 100 pounds; but the oscillator, like the ordinary electric motor, is also 

 capable of acting as a generator, and on account of its high efficiency 

 as a motor is a very efficient one. 



The same oscillator is therefore used for sending and for receiving, 

 a switch being thrown in one direction when it is desired to tele- 

 graph under water and thrown the other way when it is desired to 

 listen in. 



In addition to telegraphing and receiving messages, the oscillator 

 can also be used for telephoning under water. Sentences have been 

 transmitted at 800 yards and conversation at more than 400 yards, 

 and this was accomplished with the use of an ordinary telephone 

 transmitter and six dry cells. 



It seems evident, therefore, that with more power much greater 

 distances can be reached. Long distances are not, however, neces- 

 sary, as, even with a distance of 1 mile, it will be readily understood 

 that this method of underwater telephoning will be of great use as a 

 means of communicating between submarines while submerged and 

 between ships in fog, as the captains of the vessels can talk directly 

 to each other instead of transmitting and receiving through a tele- 

 graph operator. 



Some other uses to which the oscillator may be put may be men- 

 tioned briefly. 



One which will at once suggest itself is the steering of torpedoes 

 by sound under water. The idea of so operating torpedoes is not a 

 new one, and has occurred to a number of inventors, but until the 

 present time no method of accomplishing it has been developed. With 

 this new source of sound, however, the method should be practicable. 



Another use is as a means for obtaining soundings. If we take a 

 commutator wheel, with one live segment and two brushes, one con- 

 nected to the alternating-current generator and the other to the tele- 

 phone receiver, it will be evident that when the commutator segment 

 makes contact with the brush connected to the generator a sound 

 will be produced by the oscillator. When the live contact passes 

 away from the brush the sound will cease. This sound wave will 

 travel outward, and on reaching the bottom will be reflected and 

 travel back again to the ship. Meantime no sound will be heard in 

 the telephone receiver, but if the brush connected to the telephone 

 receiver be shifted in the direction of rotation of the commutator 

 until it makes contact with the live segment of the commutator at 

 precisely the instant at which the reflected sound wave has come back 

 and impinged on the oscillator diaphragm then a sound will be 



