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tion and depression, through long ages, of largt portions of the 

 earth's crust, is a proximate cause by which such phsenomena have 

 been explained : and this class of events, its evidence, extent, and 

 consequence, is brought before our view by Mr. Darwin's investi- 

 gations, with a clearness and force which has, I think I may say, 

 filled all of us with admiration. I may refer especially to his views 

 respecting the history of coral isles. Those vast tracts of the Pacific 

 which contain, along with small portions of scattered land, innumer- 

 able long reefs and small circles of coral, had hitherto been full of 

 problems, of which no satisfactory solution could be found. For 

 how could we explain the strange forms of these reefs ; their long 

 and winding lines; their parallelism to the shores? and by what 

 means did the animals, which can only work near the surface, build 

 up a fabric which has its foundations in the deepest abysses of ocean ? 

 To these questions Mr. Darwin replies, that all these circumstances, 

 the linear or annular form, their reference to the boundary of the 

 land, the clusters of little islands occupying so small a portion of the 

 sea, and, above all, the existence of the solid coral at the bottom of deep 

 seas, point out to us that the bottom of the sea has descended slowly 

 and gradually, carrying with it both land and corals ; while the ani- 

 mals of the latter are constantly employed in building to the surface, 

 and thus mark the shores of submerged lands, of which»the summits 

 may or may not remain extant above the waters. I need not here 

 further state Mr. Darwin's views, or explain how corals, which when 

 the level is permanent fringe the shore to the depth of twenty fathoms, 

 as the land gradually sinks, become successively encircling reefs at 

 a distance from the shore ; or barrier reefs at a still greater distance 

 and depth ; or when the circuit is small, lagoon islands: — how, again, 

 the same corals, when the land rises, are carried into elevated situa- 

 tions, where they remain as evidences of the elevation. We have 

 had placed before us the map, in which Mr. Darwin has, upon evi- 

 dence of this kind, divided the surface of the Southern Pacific and 

 Indian oceans into vast bands of alternate elevation and depression ; 

 and we have seen the remarkable confirmation of his views in the 

 observation that active volcanos occur only in the areas of ele- 

 vation. Guided by the principles which he learned from my distin- 

 guished predecessor in this chair, Mr. Darwin has presented this 

 subject under an aspect which cannot but have the most powerful 



