CLARENCE KING. 



Evolution of Environment." It was a protest against the ex- 

 treme uniformitarianism of that day, based largely on the geo- 

 logical history of the Cordilleran System as developed during 

 the work of the 40th Parallel Survey. This uniformitarianism 

 he characteristically described as "the harmless undestructive 

 rate (of geological change) of today, prolonged backward into 

 the deep past." He contended that while the old belief in catas- 

 trophic changes had properly disappeared, yet geological history, 

 as he read it, showed that the rate of change had not been so 

 uniform as was claimed by the later school. While a given 

 amount of energy must evidently be expended, he reasoned, to 

 produce a given effect, yet the expenditure of this energy might 

 be extended over a very long time or crowded into a compara- 

 tively short one ; and his observations showed him that at certain 

 periods in geological history the rate of change was accelerated 

 to such a degree that the effect upon life produced was somewhat 

 catastrophic in its nature. 



Of his great work upon Systematic Geology, the larger part — ■ 

 that which outlines the geological history of tbe Cordilleran sys- 

 tem — stands as firmly today as it did when written, as a correct 

 and authoritative exposition. In view of the circumstances under 

 which the field work was originally done, its essential correct- 

 ness, even in matters of minor detail, is considered surprising 

 by those who have since had occasion to make detailed studies 

 of portions of the area covered. 



In the more theoretical sections, while he necessarily did not 

 take into account the great number of new facts which have been 

 established by more recent work, especially in the domain of 

 microscopic petrography, he showed such grasp of his subjects 

 and such originality and power of thought that his views consti- 

 tuted not only an important advance over those of the day, but 

 they were suggestive of the lines of investigation that- have been 

 most fruitful in the modern advance of geological science. 



Eor instance, in his discussion of the reason for the changes 

 from acid to basic eruptives within the individual groups, which 

 he proposed as a variation from the natural order in age of vol- 

 canic rocks, as laid down by Eichthofen, he advanced views very 

 suggestive of the modern conception of differentiation in eruptive 

 magmas. 



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