THE DEPTHS OF THE OCEAN. 247 



spirit worthy of the representatives of a free and enlightened peo- 

 ple, had authorized the Secretary of the Navy to employ three 

 puhlic vessels to assist in perfecting the discoveries, and in con- 

 ducting the investigations conected therewith. 



690. The plan of deep-sea soundings finally adopted, and now 

 in practice, is this : Every vessel of the Navy, when she puts to 

 sea, is, if she desires it, furnished with a sufficient quantity of 

 sounding-twine, carefully marked at every length of one hundred 

 fathoms — six hundred feet — and wound on reels of ten thousand 

 fathoms each. It is made the duty of the commander to avail 

 himself of every favorable opportunity to try the depth of the 

 ocean, whenever he may find himself out upon "Hue water." 

 For this purpose he is to use a cannon ball of 32 or 68 pounds 

 as a plummet. Having one end of the twine attached to it, the 

 cannon ball is to be thrown overboard from a boat, and suffered to 

 take the twine from the reel as fast as it will. 



691. The reel is made to turn easily. A silk thread, or the com- 

 mon wrapping-twine of the shops would, it was thought, be strong 

 enough for this purpose ; for it was supposed there would be no 

 strain upon the line, except the very slight one required to drag it 

 down, and the twine having nearly the specific gravity of sea wa- 

 ter, this strain would, it was imagined, be very slight. Moreover, 

 when the shot reached the bottom, the line, it was thought (§ 676), 

 would cease to run out ; then breaking it off, and seeing how much 

 remained upon the reel, the depth of the sea could be ascertained 

 at any place and time, simply at the expense of one cannon ball 

 and a few pounds of common twine. 



692. But practical difficulties that were not expected at all 

 were lurking in the way, and afterward showed themselves at ev- 

 ery attempt to sound ; and it was before these practical difficulties 

 had been fairly overcome that the great soundings (§ 688) were re- 

 ported. In the first place, it was discovered that the line, once 

 started and dragged down into the depths of the ocean, never would 

 cease to run out (§ 677), and, consequently, that there was no 

 means of knowing when, if ever, the shot had reached the bottom. 

 And, in the next place, it was ascertained that the ordinary twine 

 (§ 687) would not do ; that the sounding-line, in going down, was 



