10 
GEOLOGY OF THE FOURTH DISTRICT. 
At one time fishes were supposed to date the commencement of their existence subsequent 
to the Coal period; nevertheless, their remains have been traced downwards through the 
Carboniferous system, the Old redsandstone, and into the middle of that vast fossiliferous 
series of the older periods known as Transition or Silurian. In New-York, the remains of 
fishes have been found in the Oriskany sandstone and succeeding limestones of the Helder- 
berg series, holding a central place in the New-York system. From the facts now known, it 
appears that trilobites were the first created animals possessing highly developed locomotive 
powers ; they being the “ lords of the earth ” till the appearance of higher organizations, as in 
the fishes. Still, subsequent facts may reveal to us the astonishing truth that fishes were among 
the earliest inhabitants of the globe, and thus that vertebrated forms held place among the 
first creations. 
Scarcely less erroneous was the opinion promulgated that the fossil remains of the older strata 
consisted of a few singular crustaceans with brachiopodous shells, or such as possessed an 
opening under the beak for the protrusion of a peduncle by which to attach themselves, as in 
Delthyris and Orthis; together with some singular forms of chambered shells, as Orthocerce, 
and others; and that the whole assemblage was so unlike the Fauna of the present ocean, 
that there was nothing existing with which to compare them. On the contrary, though the 
greater number as regards species and individuals are of types quite distinct from the most 
of those inhabiting the present ocean, yet we now know that several of the fossil genera of 
the older rocks are still living in our seas, having existed through every geological era. A 
species of the genus Lingula appears in the oldest known fossiliferous rock ; and this shell, 
with Orbicula, were among the earliest inhabitants of these ancient waters. In rocks of the 
same period, we find shells closely allied to, if not identical with, Trochus, Turbo, Buccinum, 
Nucula, Avicula, and numerous other genera; while among the living crustaceans of the 
southern hemisphere, are forms closely allied to the trilobites of this period. In fact it would 
appear that in these earlier deposits are an assemblage of fossils, as much like the Fauna of 
the present seas as in some of the subsequent geological periods. 
The doctrine of violent catastrophes, and of sudden changes in the inhabitants of the ocean, 
was based upon the examination of limited districts, where the entire series of deposits had 
never existed, or had been subsequently obliterated. And gradual and tranquil as the changes 
now seem to us, they may appear infinitely more so when a perfect sequence among the 
strata of the whole globe shall become known—when a complete succession shall be esta¬ 
blished from the oldest to the newest rock. From what we now know, compared with the 
knowledge existing a few years since, we can readily infer that some distant places, or even 
nearer localities, may furnish links now wanting in the chain. 
In learning to regard nature as always the same, and her laws unchanging, we have made 
a grand step towards the explication of phenomena before unexplained, except through a sus¬ 
pension of the natural laws, or a miraculous interposition of creative power. Nature is always 
perfect and unvarying, but man’s knowledge is progressive ; consequently in every advance 
he arrives nearer to the truth, and yet as far from knowing all nature and her laws as he is 
from Infinity. 
