20 
GEOLOGY OF THE FOURTH DISTRICT. 
The New-York System includes rocks, which, in Great Britain, have received three dis¬ 
tinctive appellations: 1, The Cambrian System of Prof. Sedgwick; which, judging from 
specimens, includes rocks lower than the Utica slate, and apparently similar to the disturbed 
strata along the Hudson river, though probably not reaching so low as the Potsdam sandstone. 
2, The Silurian System of Mr. Murchison; which embraces the rocks and groups from the 
Utica slate to the Hamilton group, and so ably and beautifully illustrated by that author. 
3, The Devonian System of Prof. Phillips ; which appears, from the numerous illustrations 
of its fossils, to correspond to the Chemung and Portage groups, and also to include a portion 
of the Hamilton.* 
The Devonian System, as usually understood in this country, is supposed to include the 
Old Red Sandstone of Europe ; but in central New-York, there is a well defined line of 
demarkation between the Chemung group and the Old Red, which contains remains of the 
Holoptychus, &c. Many of the fossils figured by Mr. Phillips are identical, and others very 
similar to those of our Chemung and Hamilton groups, while they differ widely from those of 
the Catskill, or Old Red Sandstone. 
From the absence of all extensive disturbances of the strata, we are enabled to trace an 
uninterrupted series from the Potsdam sandstone to the Old Red. No where is there known 
to exist so complete a series of the older fossiliferous rocks, as those embraced within the 
limits of the State; and terminating at a point of great and important change in the condition 
of the surface, and included between this and the rocks of metamorphic origin, we have here 
offered one of the most decided and best characterized systems known in the whole world. 
The New-York System thus becomes equivalent to what was embraced in the Transition 
by Werner, which term in modern times has been found too objectionable to retain. It like¬ 
wise includes the three systems of English authors just mentioned, leaving the Old Red 
Sandstone and Coal to a subsequent period. And this for the reason, that in New-York, 
where the means of investigation are best afforded, and where the whole series is undisturbed, 
there is manifested the most complete and continuous succession ; showing but one geological 
era for the deposition of the whole. In that era, the earth first witnessed the dawn of animal 
life, and ages of its greatest fecundity in marine organisms ; and the approach of the period 
when it became fitted to support a vegetation so luxuriant and universal, of which no modern 
era affords a parallel. 
Hitherto great confusion had prevailed regarding the rocks here enumerated as occurring 
between the Carboniferous and Primary series ; and it was not until the publication of the 
result of Mr. Murchison’s labors, that we had any definite knowledge of the sequence, in other 
places, of these extensive groups, which over thousands of miles in area are the most impor- 
* Since writing the above, I have received Mr. Murchison’s Address before the Geological Society of London, (1842,) and he 
there distinctly states that the Devonian System constitutes a portion of the Silurian, and is inseparable from it. This view accords 
perfectly with the facts here stated. In the same Address, the Cambrian System, as distinct from the Silurian, is no longer 
sustained; and the reasons are given which led to its adoption, as well as those for its abandonment. The views which have 
been long entertained here in New-York are thus unexpectedly corroborated, and the results will doubtless prove auspicious to 
the science. 
