MARCELLUS SLATE OR SHALES. 
181 
Another remarkable fact, .and which ought not to be passed over without reference, is 
the absence in New-York of the important mass of limestone known elsewhere as the 
Mountain or Carboniferous limestone : its position is between the Chemung group and the 
Old Red system or sandstone. The absence of this limestone has deprived the southern 
tier of counties of an important rock, and which, if it had been deposited in its normal 
position, would have changed the agricultural character of these counties. 
§ 2. Marcellus slate or shales. 
I have already stated that the upper part of the Onondaga limestone is charged with 
black shaly matter ; that the rock itself is black from its presence, and that thin beds of 
shale appear between the layers. Such then are the indications of change in the rock. 
With the commencement of the black shale, the change appears complete. It is, however, 
chemically a mere predominance of silico-argillaceous matter over the calcareous ; for most 
of the rock, if not the whole of it, retains sufficient lime to effervesce with mineral acids. 
The lower part of the rock is more highly charged with lime than the upper, and this fact 
agrees with other circumstances that attended the deposition of the mass. 
The Marcellus slate or shales may be thus described : Rock a slate, thin-bedded and 
fragile ; color black, and soils the fingers ; often exhales a bituminous odor when rubbed or 
broken ; undergoes an exfoliation when wet, by which process it breaks down into soil : 
calcareous matter disseminated throughout the rock. It would be impossible, from these 
characters alone, to distinguish this rock from the Utica slate, the shaly portion of the 
Trenton limestone, or the Genesee slate : its relations, and its fossils when its relations are 
concealed, furnish the only distinctive characters by which it may be known. 
This rock has excited attention in consequence of its color, and also by its containing a 
small amount of coal : hence wherever its outcrop appears, numerous excavations have 
been made, under the expectation of finding this valuable product. It is scarcely necessary 
to say that all these attempts have failed : notwithstanding this, many persons are still 
confident that they will succeed in finding coal, provided they had the means of pene¬ 
trating deep enough into the rock. 
Relations of the Marcellus slate. It reposes upon the corniferous portion of the Onondaga 
limestone, from east to Avest, and along its southern outcrop, from New-Scotland in Albany 
county, through Greene and Ulster counties,, to Pennsylvania. Above, it passes into the 
gritty and shaly portions of the Hamilton group. We have not yet been able to detect any 
change in the relations of this rock in its prolongation westAvard. In this respect it is an 
exception, as many at least of the rocks already described stand in connection Avith rocks 
in the Avestern counties which are unknown at the east. 
Places where this rock may be observed. The Helderberg range, which has become so 
universally known for its fine display of rocks, may be visited for this purpose. It is, 
hoAvever, concealed by its oavii as Avell as the debris of the succeeding rocks, in consequence 
of its fragile character. Hence, in fields, or other places unwashed by creeks, its out- 
