298 PirYSIC^\JL GEOGRAPHY OF THE SEA, AIW ITS METEOROLOGY. 



of the*Umted States frigate "Congress," afterwards, in attempt- 

 ing to sound near the same region, let go his phimmet, and saw 

 it rmi out a line fifty thousand feet long as though the bottom 

 had not been reached. There are no such depths as these. The 

 three last-named attempts were made with the sounding-twine of 

 the American navy, which has been introduced in conformity 

 with a very simple plan for sounding out the depths of the ocean. 

 It involved for each cast only the expenditure of a cannon ball, 

 and twine enough to reach the bottom. This plan was introduced 

 as a part of the researches conducted at the National Observatory, 

 and which have proved so fruitM and beneficial, concerning the 

 winds and currents, and other phenomena of the ocean. These 

 researches had already received the approbation of the Congress 

 of the United States; for that body, in a spirit worthy of the 

 representatives of a free and enlightened people, had authorized the 

 Secretary of the Navy to employ three pubHc vessels to assist in 

 perfecting the discoveries, and in conducting the investigations con- 

 nected theremth. 



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

 The plan finally iH practice, is this i Evory vessel of the navy, when 

 adopted. qIjq p^^|;g ^Q gg^^ jg^ j£ g|-^Q ^■[esires 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 favourable opportunity to 

 try the depth of the ocean, v/henever he may find himself out 

 upon "blue water." For this purpose he is to use a cannon-ball 

 of 32 or 68 pomids as a plummet. Having one end of the twine 

 attached to it, the cannon-ball is to be thrown overboard from a 

 boat or a steamer, and suffered to take the t^vine from the reel as 

 fast as it will. The reel is made to turn easily. A silk thread, or 

 the common wrapping-twine of the shops, would, it was thought, 

 be strong enough for this pm^pose, for it was supposed there would 

 be no strain upon the line except the very slight one requu'ed to 

 drag it down, and tlie twme having nearly the specific gravity of 

 sea Vv^ater, this strain would, it was imagined, be very shght. More- 

 over, when the shot reached the bottom, the line, it vras thought 

 (§ 561), 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 ivdne. 



