300 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY. 



way tell iis of. This system of circulation commenced on the third 

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

 which were " called seas ;" it will prohahly continue as long as sea 

 water shall j^ossess the properties of saltness and fluidity. 



571. In making these deep-sea soundings, the practice is to time 

 Method of making a the liimdrcd fathom marks (§ 568) as they successively 

 deep-sea sounding, g^ q^-^ . ^j^^ |^y always usiug a liuc of tlic sauic size 

 and " make," and a sinker of the same shape and weight, we at last 

 established the law of descent. Thus the mean of our experiments 

 gave us, for the sinker and twine used, 



2 m. 21' 8. as the average time of descent from 400 to 500 fathoms. 



„ 1000 to 1100 „ „ 1000 to 1100 



4 m. 29 s. „ „ „ 1800 to 1900 



572. Now, by aid of the law here indicated, we could tell very 

 The law of the nearly when the ball ceased to carry the line out, and 

 plummet's descent, -^j^en, of courso, it bcgau to go out in obedience to 

 the current and drift alone ; for currents would sweep the line out 

 at a imiform rate, while the cannon-ball would drag it out at a 

 decreasing rate. The development of this law was certainly an 

 achievement, for it enabled us to show that the depth of the sea at 

 the places named (§ 567) was not as great as reports made it. 

 These researches were interesting : the problem in hand was impor- 

 tant, and it deserved every effort that ingenuity could suggest for 

 reducing it to a satisfactory solution. 



573. As yet no specimens of the bottom had been brought up. 

 Brooke's sounding The Kuo was too Small, the shot was too heavy, 

 apparatus. rjj^(j {^ could not bc Weighed ; and if we could reach 

 the bottom, why should we not know its character ? In this state 

 of the case. Passed ]\[idshipman J. M. Brooke, United States Navy, 

 who at the time was associated with me on duty at the Observa- 

 tory, proposed a contrivance by which the shot, on striking the 

 bottom, would detach itself from the line, and send up a specimen 

 of the bottom. This beautiful contrivance, called Brooke's Deep- 

 sea Sounding Apparatus, is represented below. A is a cannon-ball, 

 having a hole through it for the rod B. Figure 1 represents the 

 rod B, and the slings D D, with the shot slung, ready for sounding. 

 Figure 2 represents the apparatus m the act of striking the bottom ; 

 it shows how the shot is detached, and how specimens of the bottom 

 are brought up, by adhering to a httle soap or tallow,* called " arm- 



* The harrel of a common qnill attacliod to the rod lias heen fonnd to answer 

 hotter. 



