VI 



Darwin 283 



geological chapters in the Origin of Species produced the 

 greatest revolution in geological thought which has occurred 

 in my time. Younger students, who are familiar with the 

 ideas there promulgated, can hardly realize the effect of 

 them on an older generation. They seem now so obvious 

 and so well-established, that it may be difficult to conceive 

 a philosophical science without them. 



To most of the geologists of his day, Darwin's conten- 

 tion for the imperfection of the geological record, and his 

 demonstration of it, came as a kind of surprise and 

 awakening. They had never realized that the record was 

 so fragmentary. And yet when Darwin pointed this out 

 to them they were compelled, sometimes rather reluctantly, 

 to admit that he was right. Some of them at once adopted 

 the idea, as Eamsay did, and carried it much further. 1 



Until Darwin took up the question, the necessity for 

 vast periods of time, in order to explain the characters of 

 the geological record, was very inadequately realized. Of 

 course, in a general sense, the great antiquity of the crust 

 of the earth was everywhere admitted. But no one before 

 his day had perceived how enormous must have been the 

 periods required for the deposition of even some thin con- 

 tinuous groups of strata. He supplied a criterion by 

 which, to some degree, the relative duration of formations 

 might perhaps be apportioned. When he declared that 

 the intervals that elapsed between consecutive formations 

 may sometimes have been of far longer duration than the 

 formations themselves, contemporary geologists could only 

 smile incredulously in their bewilderment, but in a few 



1 See his two Presidential Addresses to the Geological Society, Quart. 

 Journ. Geol. Soc. vols. xix. (1863), xx. (1864). 



