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and the evolutionist may reasonably claim that many of the 
proofs of his theory have been in this way destroyed. 
This argument, however, cannot be sustained with any con- 
fidence, when we come to look at the successive and conform- 
able strata of a single group of beds. Doubtless, the lines 
between successive strata do mark periods of time in which no 
sediment was being accumulated, but we have no proof that 
these unrepresented periods were of any very great duration. 
When we find, as we often do, two successive and closely- 
related beds in which the fossil remains are partially alike and 
partially unlike, it is begging the entire question to assert that 
the line dividing the two beds must represent a long period of 
time because of the unlikeness of the organic remains of the 
two. Until we can indicate with some preciseness the sequence 
of phenomena indicated by the sudden appearance of new 
forms of life in time, we have no right to assume that two 
successive beds are separated by a wide interval, simply because 
the upper bed contains one or more new and peculiar forms of 
life. 
It may be admitted, then, that, as regards the entire series 
of stratified deposits, so many gaps exist that the record of life 
is seriously mutilated ; and hence, supposing evolution to be 
true, many of the proofs of its operation have doubtless never 
been preserved to us, whilst many others must have been 
destroyed by denudation. On the other hand, it is to be urged 
that no such objection can, in the present state of our know- 
ledge, be brought against certain groups of fussiliferous deposits 
which we may take in certain known and explored regions. 
No such objection, for example, can be urged against a large 
portion of the palaeozoic rocks of North America. Com- 
mencing with the Clinton formation, we may pass from the 
base of the Upper Silurian to the summit of the Devonian 
series, through a thickness of some thousands of feet of sedi- 
ments, without meeting with a single unconformity or with 
any general palaeontological break. The entire scries admits of 
subdivision into a number of subordinate groups, each charac- 
terized by some peculiar fossils; so that we have a constant 
extinction of certain older types of life and a constant appear- 
ance of certain new forms. The fauna of each subordinate 
group is, however, constantly found to be closely related to 
that of the groups immediately above and below, and there is 
no positive evidence, either stratigraphical or palaeontological, 
of any long interval of unrepresented time separating the suc- 
cessive groups. In other words, so far as all the positive 
evidence would show', we have here an area which remained 
