of Bitumens, and of Bituminous Shales. 167 
great mass of dolomites, with gypsum and salt, which makes up 
the Clinton, Niagara, Guelph and Onondaga formations, repre- 
sents on a great scale the similar dolomites of the Calviferous 
formation. ‘The lithological representative of the Trenton group 
next appears in the Corniferous formation, composed, like the 
former, of pure limestones, with chert beds, silicified fossils, and 
petroleum. To these succeed in western New York the pyro- 
schists, called the Marcellus shales, closely resembling those of 
the Utica formation, and followed by the Hamilton group, lith- 
dlogically similar to that of the Hudson River, and overlaid in 
its turn, by sandstones of the Portage and Chemung group, 
Which may be compared to those of the Potsdam and Oneida 
formations.’ It should be mentioned however that the repeti- 
tion of the pyroschists at the base of these sandstones, constitu- 
ting the Genesee slates, has no known representative in the 
Lower Silurian series, 
_Itis in the Lower Devonian limestone, or Corniferous forma- 
tion, that the greatest amount of petroleum occurs, although Mr. 
Hall observed that the dolomites of the Niagara formation in Mon- 
ree county, New York, frequently contain mineral pitch; which is 
Sometimes so abundant as to flow from the rock, when this is 
heated in a lime-kiln. Coneretionary nodules holding petroleum 
have also been observed in the Marcellus and Genesee slates, 
while the higher Devonian sandstones in New York and Penn- 
sylvania are often impregnated with petroleum, and from these, 
and from still higher strata, issue the oil springs of those regions. 
“Is probable however that the source of the oil in these superior 
Strata is to be found in the Corniferous limestone, from which 
the petroleum of western Canada is undoubtedly derived, since 
M Enniskillen this formation is covered only by or 800 
feet of Hamilton shales, the Marcellus pyroschists being absent 
from that region; while at Tilsonburg the limestone appears at 
the Surface, and wells bored into it have yielded considerable 
Wantities of petroleum. Different observers have noticed th 
Cavity, lined with erystals of calcite, and filled with petroleum. 
Corailine beds itn pireiowatel with petroleum are found in Wainfleet 
: . . 
The late Prof. Eaton h tion of this curions lithological parallelism, 
< ay ada perception 0! i ygical paral 
bs successive geological series, vie . classed all stratified rocks in three divisions, 
carboniferous, quartzose and ealeareous ; which he supposed to be repeated in the 
M . B : 
series é a 
mip, wd slaty rocks, in which, according to him, eval and car haa 
Might occur, J : 9 Rams mgs Re Placed gneiss 
aig! x the f divisto he 197. xxii 
Sey crystalline schists, (Geol. Text Book, 1832, aud this Journal, [2], xxii 
