SOME ASPECTS OF GEOLOGIC TIME 263 



yet been obtained. On a very few assumptions, the actual 

 measured results must be regarded as minima. But there is 

 much research yet to be accomplished before we can be quite 

 sure what value to place upon them. So far as they go, however, 

 they support the main contention of this paper. The radioactive 

 method must be accepted as another valuable line of research. 1 



PART II.— ORGANIC EVOLUTION AND 

 GEOLOGIC TIME 



A. Biologic Theory and Geologic Time 



In the whole history of human thought, it would be difficult 

 to find two topics so intimately connected as evolution and 

 geologic time. In the days of catastrophic cosmogony, no theory 

 of evolution was possible. The discoveries of the early geologist 

 paved the way for the superstructure of the evolutionist. When 

 we discovered that the earth dated back to a remote antiquity, 

 and that, during this lapse of time, the forms of life were 

 continually changing, the naturalist was then able to investigate 

 the causes of the change. 



Thus the evolutionary ideas of Darwin were founded on the 

 uniformitarian geology of Hutton and Lyell, which postulated 

 an indefinite lapse of time, a postulate of which Darwinian theory 

 took full advantage. A number of philosophers, Lamarck and 

 Herbert Spencer in particular, had anticipated Darwin in the 

 advocacy of evolution, but had differed in their opinion of its 

 causes. By a strange coincidence, the theory of Darwin 

 demanded a vaster extent of time than had the ideas of any 

 previous worker. By laying such great stress on natural 

 selection, by postulating that, in the main, the changes in the 

 forms of animal and vegetable life were due to the selection of 

 minute and imperceptible variations which happened to be of 

 advantage in the struggle for existence, he required the assump- 

 tion that the time must be of the order that commended itself to 

 the geologists of his day. So much was this the case that, when 



1 In view of the possibility that too much stress may be laid on this, as dis- 

 tinguished from other lines of research, I think it well to say that, in my opinion, 

 though detailed criticism is outside the scope of this article, attempts to assess 

 exact times from consideration of bad ratios, are, to say the least, premature. 

 There are so many causes of uncertainty. The most that we can now infer is a 

 moderate minimum of time, a result that is given equally well by other data if 

 properly handled. 



