470 PROCEEDINGS OP PHILADELPHIA MEETING. 



intensely interested in the sinking of the mid-Pacific bottom, as indicated 

 by the coral reefs. This sinking had its correlative in the elevation of 

 the western side of the American continents, north and south, and esyie- 

 cially in the ridging uj) of their margins into the great mountains on 

 that side. 



In the above statements (1 and 2) I believe I have given substantially 

 Dana's views, although perhaps modified a little by suggestions of my 

 own mind ; but we go on. 



3. It is evident that from this general point of view the same causes 

 which originated continents and ocean basins, by continuing to act, would 

 increase the size and height of the former and the depth of the latter, and 

 therefore the places of continents and oceans must have remained sub- 

 stantially the same. Dana, therefore, was the originator of the idea of 

 the substantial permanence of the places of these greatest inequalities of 

 the earth's surface. The previous school, which may be called the school 

 of Lyell, took an entirely different view. Tlie gradual evolution of the 

 earth as a unit and of the organic kingdom as a whole was imperfectly, 

 if at all, conceived by the Lyellian school, for Darwin was not yet. Fos- 

 sils were " medals of creation " — means of determining strata — the oscil- 

 lations of the earth's crust were irregular and without law or goal ; the 

 continents and the oceans had changed places many times in the history 

 of the earth. For Dana, on the contrary, earth-forms have steadily de- 

 veloped toward their present condition. The idea of evolution was clearly 

 conceived and ap[)lied to the earth (though not to the organic kingdom) 

 by Dana long Ijefore Darwin's time. 



Dou))tless this idea of permanence of earth-fornis may be pressed too 

 far, but was never so pressed by Dana. For him it was not absolute 

 rigid permanence, for that would be contrary to the idea of evolution ; 

 for him it was permanence of thought, of plan, but carried out by devel- 

 opment, and therefore with many changes in detail. There have doubt- 

 less been many oscillations of the earth's crust, many submergences and 

 emergences of land surfaces, especially on the margins, though sometimes 

 of greater extent and affecting also the interior of continents, oscillations 

 the causes of which we do not yet understand, but with these qualifica- 

 tions and limitations the principle is now well established and generally 

 accepted. 



4. As a necessary consequence of steady contraction resisted by crust 

 rigidity, there must have been paroxysms of yielding and therefore 

 periods of readjustments of the crust to new ])Ositions,and therefore also 

 extensive changes of physical geography and corresi)onding changes in 

 organic forms. These times Dana appropriately called revolutions. They 

 are marked by the formation of great mountain-ranges. The greatest of 



