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THE POPULAR SCIENCE MONTHLY. 



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, dur- 

 ing his explorations on the west coast of Scotland during the summer 

 of 1878, brought up so many fine specimens from the mud in w^hich it 



Fig. 1. 



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 con- 

 necting 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 use- 

 ful 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, efiicient 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 



