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Page:Popular Science Monthly Volume 44.djvu/346

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THE POPULAR SCIENCE MONTHLY.

HOW THE SEA IS SOUNDED.
By G. W. LITTLEHALES.

IT was not until long after astronomers had begun to sound out the realms of space and to measure the distances and weigh the masses of the planets that the longing which has always existed in the human mind to know more of the mysteries of the sea began to be gratified. Indeed, the deep sea remained unfathomed and mysterious until after the second half of the present century had dawned upon the world; and the contemplative mariner of fifty years ago, as he looked upon the heaving bosom of the ocean and wondered at its mysteries, had nothing but myths and legends to sustain his meditation.

Under the stimulus created by the achievements in investigating the earth, the air, and the heavens attempts had already been PSM V44 D346 Modern sounding cylinder.jpgFig. 1.—Modern Sounding Cylinder. made to fathom the ocean both by sound and pressure, but in what sailors call "blue water" every trial was a failure repeated.

In 1856, Maury writes: "The most ingenious and beautiful contrivances for deep-sea sounding were resorted to. By exploding heavy charges of powder in the deep sea, when the winds were hushed and all was still, the echo or reverberation from the bottom might, it was held, be heard and the depth determined from the rate at which sound travels through water. But though the explosions took place many feet below the surface, echo was silent and the sea gave out no answer. Ericsson and others constructed deep-sea leads having a column of air in them which, by compression, would show the pressure of the water to which they might be subjected, and therefore the depth. This plan was found to answer well for ordinary purposes, but in the depths of "blue water," where the pressure is equal to several hundred atmospheres, the trial was more than these instruments could stand."

Lieutenant Maury planned and constructed an ingenious deep--