IN FAVOR OF REVEALED RELIGION. 507 
ries than the geological into periods and epochas ; nor is the 
certainty less great, or the chance of transposition in any degree 
less slight in the one case than in the other. For, respecting at 
least the main geologic systems, their order of succession, and 
the organisms which they contain, the evidence is as positive 
and conclusive as it is regarding any piece of human history 
whatever. There are, however, certain geologic inferences 
very extensively adopted, which are founded rather on nega- 
tive than on positive evidence ; and these must of necessity, be 
subject, during the course of discovery, to modification and 
change. And we find resting mainly on this department of 
the negative,—I should, perhaps, rather say of the assump- 
tive, —two of the extremer schools of the present day, — that 
school which, founding on a certain progressive rise, in the 
course of the geologic periods, from lower to higher types, both 
animal and vegetable, would infer that what we term creation 
is in reality but development,—the low, in the lapse of un- 
measured ages, having passed, it is alleged, into the high ; and 
another school, represented by at least one very masterly geolo- 
gist, which teaches that there has been no upward progress in 
creation, but that the earth, in all the periods of its history 
represented by the geologic systems, must have existed under 
the same great conditions in which it now exists, and have pro- 
duced, mingled with inferior forms, plants of the same superior 
classes, and, if we except man himself, animals of the same 
high divisions of the vertebrata. 
What, however, are the positive facts with which, as geolo- 
gists, we are called on to deal? In the Tertiary Flora we find 
great abundance of true dicotyledonous trees, —in its Fauna, 
frequent forms of the mammals, which, in at least the later ages 
of the division, are of high types. We pass into the great 
Secondary division, and find trees as abundant in its Flora, in 
at least some of the middle deposits, as in any of the Tertiary 
