126 The Bed of the Ocean. 



upon oceanic and atmospheric currents, upon climate, and upon 

 the whole fauna and flora of the region where it takes place, 

 may be readily appreciated. 



The average height of the dry land above the level of the 

 sea has been calculated to amount to less than 200 fathoms, 

 while the average depth of the ocean is probably over 2000 

 fathoms ; so that, if we deduct the mountain ranges and elevated 

 plateaux which largely contribute to the above average, a great 

 portion of the dry land must be less than 100 fathoms above the 

 level of the sea^ A depression of 100 fathoms, while it would 

 cause almost all *dry land to disappear — all but the most elevated 

 regions — would reduce the depth of the ocean by only one- 

 twentieth. In connection with this subject, it is necessary to guard 

 against an impression produced by recent discoveries of exten- 

 sive areas of great depth in the vicinity of the land, and encouraged 

 by the small scale on which the results of sounding operations 

 have to be presented to the eye. The comparatively rapid 

 increase of depth, so frequently observed beyond the loo-fathom 

 line, has suggested the idea that the continents of the old and 

 new world rise abruptly from the bottom of the sea and form 

 high plateaux, whose steep sides descend within a short distance 

 of the shore into depths of two or three and occasionally four 

 or five miles. It is but natural that a distance of five, ten, or 

 twenty miles should appear very short when compared with the 

 wide expanse of an oceanic basin ; but it will become evident, 

 to any one who will take the trouble to put down on paper the 

 proportion between distance and depth, that a depth of 1000 

 fathoms, or of one mile, at a distance of five miles from the 

 shore, by no means forms what is generally understood by 

 a "steep incline," as the angle is little over 11°. A depth 

 of one mile at a distance of ten miles is a comparatively rare 

 occurrence, and in most cases where the soundings seem to 

 increase with more than usual rapidity to depths of 2000 and 



