ONONDAGA-SALT GROUP. 
165 
which require fo be brought together before the chloride of sodium can be obtained. 
We are obliged to remain in darkness on this subject; while upon the origin of the other 
saline and acid springs, there is no doubt but that they are formed from the decomposition 
of the materials in or of the rock itself.* 
General remarks on the middle and upper members of the Helderberg division. It has been 
useful, up to this point of my description of the New-York system, to throw many of its 
series into groups, which, mineralogically considered, have some striking characters in 
common. Thus the last series described consists of four, and perhaps more members, 
which graduate into each other : they may be quite different apparently at their extremes, 
still we are unable to discover where it would be necessary to consider them as distinct 
rocks. When, however, we reach the rocks which form the Helderberg and Schoharie 
ranges, beginning with the Pentamerus limestone, we find it necessary to abandon the 
plan of throwing the series into groups, and to adopt that of describing the succeeding 
rocks as distinct individual masses. Limestones, it is true, predominate, and we might 
describe them under some such appellation as this, namely, the Schoharie limestone group , 
were it not that the limestones resemble each other so faintly, that the combination of this 
common name would form an assemblage as heterogeneous as possible. If, for example, 
we compare the Dcllhyris shaly limestone with the Onondaga limestone, we may see at 
once that they are incongruous rocks. So the same may be said of the Pentamerus and 
Onondaga limestones ; and finally, no two of the rocks can be grouped together without 
violating some principle of classification. But what still makes the difficulty greater, is the 
presence of three beds of anomalous sandstones, which, neither lithologically, nor by their 
fossils, can be associated together, or with the limestones which are adjacent to them. For 
these reasons, then, the succeeding rocks of this division are described individually as inde¬ 
pendent rocks. If, is not intended, however, by these remarks, to convey the idea that 
there is nothing in common among them ; for some fossils pass upwards through two or 
more rocks, and thus link them together by conditions which must have been somewhat 
similar at the period they were deposited. 
Mctamorphic rock. At Syracuse, a mass resembling serpentine appears in the gypseous 
rocks : it is yellowish green, passing into deep green with a tinge of blue. It softens and 
whitens on exposure to the weather. It effervesces briskly with acids, and hence contains 
considerable carbonate of lime. The interior is hard, and sometimes siliceous and ex¬ 
tremely tough. Mica, hornblende, and indeed very well characterized granite, have been 
observed in a portion of this rock.f It takes a fine polish, and would form a beautiful ser¬ 
pentine marble if it was of a uniform texture and hardness. The origin of this rock is not 
well determined. Mr. Vanuxem regards it as having been formed by a chemical union 
of its elements in solution in water. This view is adopted in preference to that of an 
* The green shales, and a part of the Onondaga-salt group, were inadvertently placed in the list of .rocks which 
compose the Ontario division, p. 1-41. 
f Vanuxem’s Report, p. 109. 
