. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. 28 DEPTHS OF THE OCEAN Thomson's sounding machine. Precautions necessary in making soundings. and of the steel line (piano wire) afterwards adopted for sounding. It will be obvious at once what a saving of space is obtained by the use of a steel line. This oo will be clear, too, if we look at Sir William Thomson's sounding machine, the principle of which is clearly illustrated by the follow- ing
. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. 28 DEPTHS OF THE OCEAN Thomson's sounding machine. Precautions necessary in making soundings. and of the steel line (piano wire) afterwards adopted for sounding. It will be obvious at once what a saving of space is obtained by the use of a steel line. This oo will be clear, too, if we look at Sir William Thomson's sounding machine, the principle of which is clearly illustrated by the follow- ing instructive figure from Sigsbee's book (Fig. 5). The wire is wound in by a large wheel consisting of a drum 2 feet 6 inches in cir- cumference between two thin galvanised iron plates 6 feet in circumference, the object of making this wheel of such a size being to enable the line to be paid out and hauled in quickly. In taking soundings the art consists in getting the wheel and line to stop the moment the plummet touches the bottom. Fig. 4.—Sounding-Line and Wire. a and b, Circumference of the hemp sounding-line of the "Challenger" ; c, piano wire. (From Sigsbee.). Fig. 5.—Thomson's Sounding Machine. (From Sigsbee.) The line drifts when free of the lead, as it is, of course, relieved of the weight as soon as the bottom is reached, but there still remains the weight of the line itself, while the momentum of the wheel will cause it to continue revolving for a little while. The wheel must consequently be made as light as possible, and a resistance of some sort must be provided, rather stronger at. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Murray, John, Sir, 1841-1914; Hjort, Johan, 1869-. London Macmillan
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