282 
IMPEEFECTION 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 suflSced 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, which the 
future historian will recognise as having produced a 
revolution in natural science, yet does not admit how 
incomprehensively 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 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 
