104 TRANSACTIONS OF THE [Frs. 23 
_ limestone*. In another place+ he speaks of the sandstone as 
lying unconformably upon the primary. 
Brooks was led by his observations in Rossie, to conclude 
that the limestone was conformable with the sandstone, and, 
therefore, of Lower Silurian, or, as it would now be called, 
upper Cambrian age. The data upon which Brooks based his 
conclusion seems to the writer unreliable ; for at Rossie the 
limestone and sandstone are separated by considerable bodies 
of iron ore and a peculiar serpentine rock of doubtful origin. 
Until the true character of this member of the series is ascer- 
tained, it is unsafe to base conclusions upon observations made 
at that locality. 
North of Gouverneur the limestone and sandstone are in 
direct contact, and opportunity is afforded for a study of their 
relations. The evidence here presented, though often obscured 
by the character of the rocks; indicates unconformity. From 
the irregular line of contact it is clear that the material of the 
standstone was deposited upon a limestone surface that had 
been subjected to erosion. An interesting confirmation of this 
conclusion is seen in the presence of narrow, irregular cracks 
extending several feet into the limestone and filled with sand- 
stone. Evidently the limestone was completely lithified, and 
not a calcareous ooze, when the sandstone was deposited upon 
it, and this implies discordance. 
This unconformity proves only that the limestone is older 
than upper Cambrian, For any more definite determination of 
its age the data are wanting. 
Granite.—In the southern part of the area examined granite 
forms a prominent ridge extending east and west. Besides this 
main mass, there are many small patches breaking through the 
limestone, some of these consisting of a pegmatitic variety. 
Emmons’ theory of the igneous origin of limestone was largely 
based upon the character of the contact between the main body 
of granite and the surrounding limestone. He regarded the 
granite as a massive phase of the gneiss, and, holding the latter 
to be sedimentary, was forced by the undoubted irruptive 
contact between granite and limestone to look upon the latter 
as igneous. Were the identity of gneiss and granite a fact, 
a ready explanation of the origin of the former would be 
* Geology of N. Y., 2d District, p. 53. 
t Fourth Ann. Report, Geol. Survey of N. Y., p. 322. 
+ American Journal of Science, iii., TV., p. 22. 
