198 
DEVONIAN SYSTEM, 
VI. THE UPPER ROCKS OF NEW-YORK EQUIVALENT TO TI1E DEVONIAN 
SYSTEM OF ENGLAND AND THE CONTINENT. 
Mr. Conrad was the first American geologist who perceived the equivalency of the upper 
New-York rocks, to those which were described by Mr. Phillips under the name of Devo¬ 
nian. To him also is to be given the credit of identifying the Silurian system with the 
lower rocks of this State. When the outlines of resemblance have been traced, it requires 
only diligence and moderate capacity to fill up the details. While it is admitted, however, 
that the New-York and Silurian rocks have been proved by American geologists to belong 
to a coeval period, it is not proved that the two are identical. Such a closeness of agree¬ 
ment, in such distant rocks, could not be expected. This much seems to be established, 
namely, that the rocks of the two continents, limited upwards by the Coal series, and by 
the Taconic system below, were deposited during the same period ; but whatever of a mo¬ 
difying nature existed in either continent, had its influence on each series respectively. 
A prolongation of a particular deposit beyond the corresponding one of a distant continent, 
often took place. Intercalated members appear in a few instances. Organic beings were 
formed on the same types, but rarely identical. While resemblances were preserved in the 
greater number, the novelties were rarely common. As New-Holi and must have her 
kangaroos, and quadruped-like forms in her aviaries ; the Galapagos, their lizard forms; 
and Africa and America, each their peculiar faunas; so analogy forbids our expectancy 
that the faunas of our two silurian worlds shoidd be identical. It is not a variety, however, 
which arises from necessity, from obedience to physical causes : the variety exists for 
variety’s sake, and to fill creation with diversified grades of being. 
The advancement of geology in this country received a new impulse, when its cultiva¬ 
tors began to study our rocks independently of European formations. So long as investi¬ 
gations were directed towards identification with foreign rocks, just so long our own for¬ 
mations remained unknown to us, perhaps from the want of proper characters by which 
they could be made out. The study of fossils has, in later years, been followed by a real 
progress in the science of geology ; and this has arisen, not so much from the use of fossils 
as characteristics, as from an independence which they gave to the thoughts and methods 
of observers. They gave us the power to compare our rocks with each other at distant 
points, and to work out our system on a basis which is truly American, and which has 
really created an American geology. This result has been practically of great value here, 
in addition to the confirmation of leading principles which had preceded it abroad. We 
have now our Silurian and Devonian systems sufficiently well defined to answer all the 
ends of science. The work of accurately identifying strata may go on, now that correct 
outlines have been marked out, and our great landmarks are so well defined. 
