Chap. X.] GEOLOGICAL KECOED. 51 



and the principle of competition between organism and 

 organism, between child and parent, will render this a 

 very rare event ; for in all cases the new and improved 

 forms of life tend to supplant the old and unimproved 

 forms. 



By the theory of natural selection all living species 

 have been connected with the parent-species of each 

 genus, by differences not greater than we see between 

 the natural and domestic varieties of the same species 

 at the present day; and these parent-species, now 

 generally extinct, have in their turn been similarly 

 connected with more ancient forms ; and so on back- 

 wards, always converging to the common ancestor of 

 each great class. So that the number of intermediate 

 and transitional links, between all living and extinct 

 species, must have been inconceivably great. But 

 assuredly, if this theory be true, such have lived upon 

 the earth. 



On the Lapse of Time, as inferred from the rate of 

 Deposition and extent of Denudation. 



Independently of our not rinding fossil remains of 

 such infinitely numerous connecting links, it may be 

 objected that time cannot have sufficed for so great an 

 amount of organic change, all changes having been 

 effected slowly. It is hardly possible for me to recall 

 to the reader who is not a practical geologist, the facts 

 leading the mind feebly to comprehend the lapse of time. 

 He who can read Sir Charles Ly ell's grand work on the 

 Principles of Geology, which the future historian will 

 recognise as having produced a revolution in natural 

 science, and yet does not admit how vast have been the 



