Page:Popular Science Monthly Volume 89.djvu/725

 Telegraphing Through the Ocean

So that ships may avoid one another in a fog, Christian Berger converts them into huge vioHns which send out sound-wave signals

��THE small-town American bo\' has a noise-making io\', which for sim- plicity, cheapness, and, above all, effectiveness, can hardly be surpassed. The principal components of the con- trivance are: one tomato- can, one string, one lump of resin, and plenty of muscle in the small boy's right forearm.

Into a hole in the bottom of the tomato-can the string is run, a lumpy knot on its inner end pre\enting it from slipping completely through. This leaves a long, dangling cord when the ex-tomato-con- tainer is held outward in the boy's left hand. With his right he grasps the lump of resin and com- mences to stroke the string.

A responsive "ee-ee-eek" emerges from the mouth of the can at the beginning of the stroking process. Shrieks, cat-calls and strident, earsplit- ting wails can be made to follow the "ee-ee-eek."

In a sense the contrivance is not unlike a violin. The can is a resonator; so is the violin body. The string is rubbed to make a sound ; so is the

��The harder he pulls the more distracting the noise

��The the

��fundamental same.

��catgut of a violin, principle invoK'ed C u r i o u s 1 \' enough, a contri- vance operating very much on the same principle has been found to be one of the most effective submarine signaling devices yet brought out. The machine in

question is the invention of Mr. H. Christian Berger, a New York physicist. It has been put in successful service on

��a number of American vessels, some of them warships — despite its resemblance in principle to the tomato-can toy or the violin. It is the result that counts. Mr. Berger's device employs either a narrow steel strip or else a piano wire as the vibrating member, this serving the same purpose as the string in the case of the can-toy or violin. One end of the wire is attached to a I^late in the steel hull of a \essel, the other end being fastened to a similar plate on the opposite side, or else terminating in a frame- work affixed to a conven- ient beam. The steel plate in the side of the vessel acts as a sounding-board to send sound-waves out into the water, just as the bottom of the tin can sends waves into the air. Instead of a lump of resin in the hands of a small boy as the exciting agency for the vibrating strip, this contri\-ance employs a motor-driven rubbing-wheel, the felt-covered rim of which is the equivalent of a violin bow and is moistened with alcohol in order to proxide an efficient rubbing medium. Although the motor which dri\cs this wheel runs continuousK-, the wheel itself mav be started and

����SKETCH SHOWINO DIFf[R[NC[ BE TWEfN AIR BELl 4ND 5U5MARINE

Btll

��stopped at will by means of a telc- graph-key control- ling an electromag- netic clutch moun- ted on the motor- shaft. Thus a telegraph-ke\- governs the send- ing of x-ibrations

just as in wireless telegraphy.

The question naturally arises: Ot

what use is a submarine signaling

���few feet under water a bell's sound loses its characteristic bell-like tone

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