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GEOLOGY OF THE FOURTH DISTRICT. 
CHAPTER XXIY. 
On the identity of the Neiv-York Formations with those of Europe. Table of 
equivalents in American strata. 
Something has already been said upon the identity of the rocks of New-York with those of 
Europe, and particularly with those of England and Wales. From the very fully illustrated 
work of Mr. Murchison, we are made acquainted with many fossils holding the same relative 
position in the rocks of England that similar species do in this country. The general litholo¬ 
gical characters of many of the successive strata correspond with those of New-York, and it 
is very natural that we should endeavor to find sufficient resemblance to identify them as of 
the same geological periods. For the great systems this has already been done, and there 
remains no doubt but the sedimentary rocks of New-York correspond with those of the Silu- 
rean and Old Red systems, as described in the Silurian Researches. If the Devonian 
is to be regarded as a distinct system, we shall find its representative in the Chemung and 
Portage groups, with, perhaps, a part of the Hamilton Group. In New-York, however, as 
already stated, no subdivisions can be made which are entitled to the name of systems. 
In regard to the identity of minor subdivisions, some obscurity still exists; though there 
can be no doubt of their correspondence, in all important particulars. When we more fully 
investigate the organic contents of our rocks, we shall doubtless find many more species com¬ 
mon to the strata on both sides of the Atlantic. 
In the rocks of the United States, there appears to be a much greater number of fossils 
than in rocks of the same age in Europe. In many instances, too, it happens that the typical 
species, upon the other side of the Atlantic, are very rare or obscure in New-York and else¬ 
where, and from the multitude of other forms, they might almost be overlooked. We have, 
however, made great advances in identifying individual formations and strata, and our pro¬ 
gress in this respect is very gratifying. 
The following tabular arrangement corresponds, very nearly, with the relative position of 
the rocks of the two systems in Great Britain and New-York 
