282 IMPEKFECTION OF THE Chap. IX. 



day ; and these parent-species, now generally extinct, 

 have in their turn been similarly connected with more 

 ancient species; and so on backwards, always con- 

 verging 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 this earth. 



On the lapse of Time. — Independently of our not 

 finding fossil remains of such infinitely numerous con- 

 necting links, it may be objected, that time will not 

 have sufficed for so great an amount of organic change, 

 all changes having been effected very slowly through 

 natural selection. It is hardly possible for me even to 

 recall to the reader, who may not be a practical geo- 

 logist, the facts leading the mind feebly to comprehend 

 the lapse of time. He who can read Sir Charles Lyell's 

 grand work on the Principles of Geology, winch the 

 future historian will recognise as having produced a 

 revolution in natural science, yet does not admit how 

 incomprehensibly vast have been the past periods of 

 time, may at once close tins volume. Not that it suffices 

 to study the Principles of Geology, or to read special 

 treatises by different observers on separate formations, 

 and to mark how each author attempts to give an in- 

 adequate idea of the duration of each formation or even 

 each stratum. A man must for years examine for 

 himself great piles of superimposed strata, and watch 

 the sea at work grinding down old rocks and making 

 fresh sediment, before he can hope to comprehend any- 

 thing of the lapse of time, the monuments of which we 

 see around us. 



It is good to wander along lines of sea-coast. 

 when formed of moderately hard rocks, and mark the 



