266 The Lapse of Time. Chap. x. 



had undergone a vast amount of change ; and the principle of com- 

 petition 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 backwards, 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 finding 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 Lyell's grand work on the Principles 

 of Geology, which the future historian will recognise as having pro- 

 duced a revolution in natural science, and yet does not admit how 

 vast have been the past periods of time, may at once close this 

 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 

 inadequate idea of the duration of each formation, or even of each 

 stratum. We can best gain some idea of past time by knowing 

 the agencies at work, and learning how deeply the surface of the 

 land has been denuded, and how much sediment has been deposited. 

 As Lyell has well remarked, the extent and thickness of our sedi- 

 mentary formations are the result and the measure of the denu- 

 dation which the earth's crust has elsewhere undergone. Therefore 

 a man should examine for himself the great piles of superimposed 

 strata, and watch the rivulets bringing down mud, and the waves 

 wearing away the sea-cliffs, in order to comprehend something 

 about the duration of past time, the monuments of which we see 

 all around us. 



