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Page:Popular Science Monthly Volume 19.djvu/72

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pounds the sounding may be completed in from twenty-five to thirty minutes. Wire, however, is less flexible than hemp, and breaks under the influence of kinks and twists, which do not affect the strength of hemp in any degree. The balance of advantages is in favor of wire, but it is well to have ropes of both kinds.

The anchor used by the author for holding his vessel in place, during his explorations on the west coast of Scotland during the summer of 1878, brought up so many fine specimens from the mud in which it

Fig. 1.

PSM V19 D072 Mud encrusted anchor.jpg

sank before taking hold on the bottom, that he determined to provide himself with one which should retain the mud. For this purpose he had an anchor made with an open frame, instead of a solid bar connecting the two palms, to which was laced a stout canvas bag, into which any mud sticking to the palm at the moment of its breaking out of the ground would fall (Fig. 1). The instrument proved a useful one for exploring the bottom, particularly when the object was to collect the mud itself rather than the things living on its surface, and was, moreover, efficient as an ordinary kedge-anchor.

Doubts have sometimes been thrown on the trustworthiness of deep soundings with the line and heavy sinker. First, it was asserted that under some great pressure the density of water would become