152 The American Geologist. st^ptemiM^r, i89? 
It is not probable tlmt aii}' of these early paleontologists under- 
stood the full meaning of this sequence, and we are hardly yet 
able to see how much the studies of the paleontologist have done 
to establish the derivative theory of evolution. But it is becom- 
ing every day more and more apparent that the reason for its great 
value to geology and for the graudness of the scope of paleontol- 
ogy is the fact that its subject matter is the records of the historj' 
of organisms. 
To the comparative paleontologist, fossils are hieroglyphics, 
which tell more fully than those of Egypt and Persia of the hab- 
its, customs, migrations and environments of the successive races 
from the beginning of the world. Although the stratigraphic 
order is all important in reading them, when the clue to the story 
is found, the fossils are as much more important than the strati- 
graphy (to the correct interpretation of geology) as the meaning 
of a sentence is more important than the succession of the words 
on the page. 
But I speak here of the scope of the pure science. Before 
this audience I would call particular attention to the value of com- 
parative paleontology to the geologist, as a means of determining 
the structure and development of the earth. 
Lyell was the first to use paleontology as a means of classify- 
ing geological formations. In establishing the divisions of the 
Tertiary, /. e. , Eocene, Miocene and Pliocene, he made a numer- 
ical comparison of the faunas themselves. This method has its 
imperfections, but the fundamental truth underlying its applica- 
tion is that there is a natural order of succession in the history of 
organisms whose remains are preserved in the strata. This order 
of succession is observable in respect of three different sets of 
characters : 
(1.) The parts or or^a/^.s of which each individual organism is 
composed. 
(2.) The separate species existing at any particular time. 
(3. ) The combination of species into faunas or floras which are 
associated with certain conditions of environment. 
In the first case we know how the organs arise, not ready made, 
but in each individual by gradual modification of the organless 
germ one after another the various parts and organs of the adult 
are perfected. The paleontologist has learned that in some gen- 
eral way, at least, the natural sequence of form of organs has 
