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5. THE DEPTH, TEMPERATUEE, ETC., OF THE NORTH 



ATLANTIC OCEAN * 



DEEP-SEA. SOUNDING. — Previous to the introduction of submarine 

 telegraph cables, comparatively little had been done in the way of sys- 

 tematically exploring the depths of the ocean, and much doubt was held 

 regarding the correctness of many of the deep soundings taken. In the 

 earlier experiments, which were made with small line quite incapable of 

 bringing back the lead, it is evident that at times the indication of having 

 reached the bottom, by the line ceasing to run, could not be altogether 

 satisfactory. 



It was formerly considered that the lower stratum of ocean-water in 

 great depths was, from the pressure and weight of the incumbent mass, so 

 dense as to be rather of the nature of solid matter than the natural fluid. 

 However, a few facts will serve to dispel such a notion. The descent of 

 the deep-sea lead is quite as rapid at a depth when the upper weight must 

 be enormous, as at less distances from the surface, and no tendency to 

 obstruct its downward passage can be observed at the greatest depth yet 

 attained, except that which is due to the friction on the sounding-line. 

 Again, the whale-fishers frequently find their prey to descend perpen- 

 dicularly to such enormous depths, that the idea of an impenetrable den- 

 sity, or even of any considerable increase of it, cannot be for a moment 

 entertained. 



It is true that the pressure increases with the depth, to the amount of 

 15 lbs. upon the square inch for every 34 feet in depth, or 225 lbs. for 

 every 100 fathoms, which is a little over 1 ton on the square inch for every 

 1,000 fathoms ; but the density is not thereby sensibly increased, owing - 

 to the comparative incompressibility of water; so that neither the buoyant 

 force, nor the resistance to the motion of any body, are materially in- 



* The chief authorities consulted on the subjects dealt with in this Section are as 

 follow:—" The Atlantic Deep-Sea Bed and its Denizens," by Dr. G. C. Wallich, 1SG4 ; 

 " The Depths of the Sea," 1873, and " The Voyage of H.M.S. Challenger; the Atlantic," 

 2 vols., 1877, by Sir G. Wyville Thomson ; " Thalassa ; an Essay on the Depth, Tem- 

 perature, &c., of the Ocean," by J. J. Wild, 1877; "Notes by a Naturalist on the 

 Challenger, by H. N. Moseley, 1879 ; " Deep-Sea Sounding and Dredging," by Lieut. 

 C. D, Sigsbee, U.S.N. , 1880, well illustrated with photographs ; " On Deep-Sea Sound- 

 ing, in Connection with Submarine Telegraphy," a Paper read before the Society of 

 Telegraph Engineers, by E. Stallibrass, 1887 ; " Den Norske Nordhavs-Expedition, 

 1876—1878," part xviii., 1887, (in English) by Dr. H. Mohn, on "The Depth, Tem- 

 perature, and Circulation of the Northern Ocean ;" " Three Cruises of the U. S. Coast 

 Survey Steamer Blake," 2 vols., by Alexander Agassiz, 1888, profusely illustrated with 

 sketches of apparatus, forms of deep-sea life, &c.;" " Oc^anographie (Statitjue)," by 

 M. J. Thoulet, 1890, a most interesting work;" the " Keports on the Scientific Results 

 of the Voyage of H.M.S. Challenger," a series of monumental richly illustrated volumes, 

 including that on " Deep-Sea Deposits," by Dr. J. Murray and Prof. A. F. Renard, 

 1891, and those on " Physics and Chemistry," 2 vols. ; and, lastly, " Geophysikalische 

 Beobachtungen der Plankton-Expedition," by Dr. 0. Kriimmel, 1893. " Fauna of the 

 Deep Sea," by S. J. Hickson, M.A., 1894, contains, in a small compass, a great deal of 

 interesting matter concerning the deep sea and its inhabitants. 



