1 6 Depth of the Ocean. 



oceanic basins, bpt, on the contrary, upon their confines, and 

 in close proximity to the land. This remarkable circumstance 

 suggests the idea that such areas of maximum depression may 

 be the effect of a sinking of the bottom of the sea in compensa- 

 tion for an upward movement of the land in their immediate 

 vicinity. 



Configuration of the Sea-Bottom. — Just as the results of 

 the recent soundings have rendered the existence of depths from 

 six to nine miles, as formerly reported, highly improbable, so 

 have they modified our ideas of the shape of the sea-bottom. 

 The latter Mras generally represented as a repetition of the dry 

 land virith its combination of mountain, valley, and plain, a view 

 not a little encouraged by the necessarily exaggerated scale of 

 the oceanic sections which have appeared in print. The vertical 

 scale is frequently from twenty- five to a hundred times in 

 excess of the longitudinal distance, since otherwise it would be 

 difficult to represent graphically a rise or fall of a few miles in 

 distances measuring several hundred miles. No doubt the 

 sea-bottom within a short distance of the shore naturally forms 

 a continuation of the leading features of the adjoining land. 

 Thus a large plain or a low-lying country will, as a rule, 

 continue its almost level slopes to a considerable distance 

 out to sea, whilst a range of hills or a chain of mountains 

 often extends its steep inclines below the surface of the water. 

 A comparison of the eastern and western coasts of the British 

 Islands will afford a ready illustration of the above remarks, and 

 examples abound in every part of the world. With regard, 

 however, to the more central portions of the bottom of our 

 oceanic basins, this conception of steep slopes and abrupt 

 changes of level within short distances is not borne out by the 

 form of the numerous oceanic sections which have been sur- 

 veyed. Those who have followed day after day the results of 

 sounding operations in mid-ocean, along sections measuring 



