60 
PALAEONTOLOGY OF NEW-YORK. 
all the great periods of sedimentary deposits which we have considered, 
or the transportation of shore-derived materials, this law has held 
true, and has governed the distribution, or the cause that originated 
these conditions, long before the distribution and deposition of the 
material commenced, giving form and contour to the eastern part of 
our continent, to its mountain ranges, and their elevation. 
It may further be observed that the Coal measure formation is the 
last which has followed this order of distribution. 
In contemplating the origin and character of the sediments forming 
the Coal measures of the United States, we are at once impressed with 
the fact that they consist largely of land-derived materials, and that 
plants of land origin mark the successive beds of which they are com¬ 
posed. Here, then, we have positive evidence of that condition of things 
which was before inferred in the lower formations. It is seen that 
in the period of the Hudson-river group, we have coarse and fine sedi¬ 
ments, evidently of shore origin, or at least from land near the surface 
of the ocean. These deposits are marked only by a marine fauna, and 
the few plant-like bodies are like the Fuci or seaweeds of modern times. 
No plant of land growth has been seen in the deposits of this age. It is 
not until we come to the Hamilton group that we find remains of land 
plants, few and fragmentary (in the State of New-York), as if drifted 
far out to sea from some sparse flora of a recent land. In the Portage 
or Chemung groups we have a larger number of species, and numerous 
specimens, all appearing as if far drifted. As we rise in the series there 
is a gradual increase in the flora, or the waves of the abrading ocean 
and the tranporting currents have farther encroached upon the land 
from which they are derived. Towards the west these remains disap¬ 
pear, and I am not aware, at this time, that any fragment of a plant 
has been found in either the Hamilton, Portage, or Chemung groups 
in the Mississippi valley. 
On the other hand, when we trace these strata towards the northeast, 
or in the direction which we suppose may have been their source, the 
fragments of plants become more numerous and the flora of larger size. 
