MEMOIR OF JAMES D. DANA. 467 



truthfulness which poison the lifeblood and sap the vitality of nations 

 are hardly regarded. Even so volcanoes and earthquakes strike the 

 imagination and fill the pages of geological literature, while the slowly 

 accumulating and far grander effects of crust oscillations hardly arrest 

 attention; and yet it is by these alone that continents and ocean basins 

 have been gradually formed. 



Now it was just these slowly acting causes and these grander effects 

 that took strongest hold on Dana's mind. Igneous agencies became for 

 him the interior vital forces of the earth, which, reacting on the exterior 

 crust, produced the greater features, and b}^ their eternal conflict with 

 external, sun-derived, sculpturing forces determine the evolution of the 

 earth as a whole. 



The mention of this line of his thought introduces us naturally to the 

 next head, and that the one which most deeply interests this Society, 

 namely, Dana as a geologist. 



Professor H. S. Williams has already given an admirable account of 

 this in the Journal of Geology for September, 1895. I am indebted to" 

 him for much that follows. For other details I would refer the reader 

 to that article. 



As already said, the idea underlying all Dana's geological work is that 

 of development of the earth as a unit. Before Dana, geology was doubt- 

 less in some sense a history — that is, a chronicle of interesting events ; but 

 with Dana it became much more, it became a philosophic history, a life 

 history, a history of the evolution of the earth, and of the organic king- 

 dom in connection with one another. For the first time there was recog- 

 nized a time-cosmos governed by law as the true field of geology, as the 

 space-cosmos governed by law is the field of astronomy. Before Dana, 

 geology was the study-of a succession of formations; with Dana it was 

 the study of a succession of eras, periods, epochs during which geographic 

 forms and organic forms were both developing toward a definite goal. 

 The underlying idea of his geological work, I repeat, was the evolution 

 of the earth as a whole. 



It is necessary to stop a moment here to qualify and explain. It is 

 true that he made a difference between the evolution of the earth and 

 that of the organic kingdom. It is true that while the development of 

 the earth was regarded by him as a natural process and determined by 

 natural causes, and therefore a true evolution, at first and for a long time 

 he regarded the progress of the organic kingdom as belonging to a dif- 

 ferent category, as not an evolution in the true sense of the word — that 

 is, not as a wholly natural process determined by natural forces residing 

 in the thing evolving. Like Agassiz, he preferred to liken the develop- 



