Page:A Treatise on Geology, volume 1.djvu/345

 CHAP. VI.

The elevated portions of the borders of the modern oceans which have been noticed, are so fraught with instructive analogies to the processes of nature in more ancient times, that we cannot help feeling regret at the limited means which man possesses of penetrating the great deep, and watching the phenomena which happen on its quiet bed. There we should behold, it is probable, a number of circumstances connected with the life of marine mollusca, radiaria, Crustacea, fishes, which would throw quite a new light on many of the problems of old geology; inform us of the probable depths, distance from the shore, and river mouths, and other conditions most important for us to know in constructing trustworthy inferences regarding the formation of the fossiliferous rocks.

Coral Reefs.—That the very deep parts of the sea (nine miles is a probable estimate for the Atlantic depths) are as devoid of life as the centre of an African desert of moving sand, is extremely probable, from the known fact of the dependence of organic life on air and light; the former must be greatly modified, the latter extinguished, in passing through such a mass of absorbent fluid. The voyagers of modern date (captain Beechey, MM. Quoy and Gaimard, Freycinet, Stutchbury, Darwin) concur in removing one error of importance on this subject; they have rendered it highly probable that the coral reefs and coral islands which abound so much in the Pacific Ocean, do not rise from even the depth of many hundred yards, but commence on the summit of some volcanic elevations, or other submarine ridges and rocks, not far below the surface of the sea.

These coral islands and reefs, which may be viewed as lines of islands, are certainly remarkable for their extent and mass of matter, even as compared with the ancient calcareous rocks, which derive much of their