156 The Ocean — its Currents, Tides, Depth, 



As the phenomena of tides, currents, winds, and the con- 

 dition of the atmosphere and ocean are in great measure de- 

 pendent on the outline of the solid portion of the earth, so 

 has this year brought with it the most remarkable hydro- 

 graphical observation of modern times, in the detection of an 

 abyss in the ocean said to be nearly double the depth of any 

 of which we previously had a conception. 



Hitherto, indeed, it had been the prevalent belief (an 

 opinion supported by Laplace himself), that the depressions 

 of the crust beneath the ocean were probably of about the 

 same extent as the elevations above the sea. Some obser- 

 vations of our scientific associate, Captain Denham, R.N., 

 have, however, gone far to modify if not to set aside this 

 hypothesis. By soundings* in the ocean, midway between 

 the Cape of Good Hope and Tristan d'Acunha, he has con- 

 cluded, after several times dropping the plummet, and by 

 finding the line always stop at the same point, that the sea 

 has there the enormous depth of 7706 fathoms, or double 

 the height of Chimborazo, the giant of the Andes. 



It is also a triumph of nautical skill and perseverance 

 that the " Herald," and her companion the " Torch" steamer, 

 should have been enabled to lie at anchor more than three 

 weeks on the comparatively shallower banks in the middle of 

 the wide Atlantic ocean, such a position having greatly 

 astonished those mariners whose course happened to cross 

 these new and unheard-of anchoring grounds. When so 

 stationed Captain Denham further ascertained, by sending 

 down thermometers, that, whilst the surface-water was at 

 90°, the cold never exceeded 40° at any depths which were 

 sounded. In addition to important magnetical observations, 

 he has excited great interest amongst geologists by proving, 

 that, within one cast of the lead, coral reefs rise suddenly 

 like a wall, from no bottom at 200 fathoms to 19 fathoms 



* The soundings were made with peculiar lines given to him by Commodore 

 M'Keever of the United States Navy. But I must state that some naval sur- 

 veyors are of opinion, that the results may have been more or less deceptive, in 

 consequence of the line not lying in a straight direction between the ship and 

 the plummet, whether by the vessel drifting during so long an operation, or by 

 the influence of currents and other causes. 



