THE DEPTHS OF THE OCEAN. 311 



and that, consequently, the twine to be used must be strong ; 

 it was therefore subjected to a test which required it to bear 

 a weight of at least sixty pounds freely suspended in the air. 

 So we had to go to work anew, and make several hundred 

 thousand fathoms of sounding- twine especially for the purpose. 

 It was small, and stood the test required, a pound of it measur- 

 ing about six hundred feet in length. The officers intrusted 

 with the duty soon found that the soundings could not be made 

 from sailing vessels with any certainty as to the depth. It was 

 necessary that a boat should be lowered, and the trial be made 

 from, it ; the men with their oars keeping the boat from drifting, 

 and maintaining it in such a position that the line should be "up 

 and down " the while. That the line w^ould continue to run out 

 after the cannon-ball had reached bottom, was explained by the 

 conjecture that there is in the ocean, as in the air, a system of 

 currents and counter currents one above the other, and that it 

 was one or more of these submarine currents, operating upon the 

 bight of the line, which caused it to continue to run out after the 

 shot had reached the bottom. In corroboration of this con- 

 jecture, it was urged, with a truth-like force of argument, that it 

 was these under currents, operating with a " swigging " force 

 upon the bights of the line — for there might be several currents 

 running in different directions, and operating upon it at the same 

 time — which caused it to part whenever the reel was stopped 

 and the line held fast in the boat. 



o70~. Evidence in favour of a regular system of oceanic circulation. 

 — A pow^eiful train of circumstantial evidence was this (and 

 it was derived from a source wholly unexpected), going to 

 prove the existence of that system of oceanic circulation which 

 the climates, and the offices, and the adaptations of the sea 

 require, and which its inhabitants (§ 465) in their mute way 

 tell us of. This system of circulation commenced on the third 

 day of creation, with the " gathering together of the waters," 

 which were " called seas ;" it wdll probably continue as long- 

 as sea water shall possess the properties of saltness and 

 fluidity. 



571. Method of making a deep-sea sounding. — In making these 

 deep-sea soundings, the practice is to time the hundred fathom 

 marks (§ 568) as they successively go out; and by alw^ays using 

 a line of the same size and " make," and a sinker of the same 

 shape and weight, we at last established the law of descent. 



