No. 161.] 
bluish color, compact, with a clean conchoidal fracture, and glitter- 
ing with small sparry points and veins. Considered as a rock, it is 
a pure limestone, containing organic remains in very few instances. 
It is extremely durable, and scarcely affected by atmospheric ex- 
posure, and occurs in layers from two to four feet in thickness. It 
usually accompanies the calcareous sandstone in our district, be- 
ing thickest where it overlies and faces the primary near Little- 
Falls, where m a ravine 30 feet are exposed in a nearly perpendi- 
cular section, and it thins out and disappears in its eastern prolon- 
gation on the line of the canal. The gray sparry limestone, is, we 
believe, that which is termed " sparry limerock" by Eaton. In its 
pure state, we noticed it at Amsterdam, in the cjuarries about two 
miles north of the village j at Tribes' Hill and at Canajoharie, from 
which latter place it is sent to Utica, Albany and other cities, 
where it is esteemed as a valuable building material, making hand= 
some columns, &c. 
4. Blue FcBtid Limestones and Shales of Trenton-Falls* 
To the sparry limestone succeed dark blue limestones and 
shales, the whole mass probably about four hundred feet in thick- 
ness, composing the summits of most of the slopes which descend 
to the valley of the Mohawk, in Herkimer and part of Montgome- 
ry counties. The rock is here chiefly a fissile slate, but as it pass- 
es to the north, it assumes, as at Trenton-Falls, the character of a 
dark blue very hard foetid limestone, crowded with organic exuviae, 
chiefly bivalve shells and fragments of trilobites. The rock has 
here been cut through by a branch of West Canada creek, which 
thus, in a succession of beautiful cascades, leaps through a deep 
gorge between perpendicular black walls. The wild grandeur of 
the scene has given it peculiar attractions for the fashionable tou- 
rist, and the organic remains will always add an additional charm 
to the spot, in the estimation of a geologist. These are the same 
species which characterize the upper mass of the dark slate on Flat 
creek, in Montgomery county, near Spraker's basin. The slate is 
frequently traversed by veins of calcareous spar, which appear 
to have filled the narrow parallel fissures, universally prevalent in 
this and many other rocks. 
On Flat creek, about one mile south of Spraker's basin, we ob- 
served three vertical veins of iron pyrites, mixed with calcareous 
spar, in which sulphuret of lead is disseminated in small masses. 
This phenomenon tends strongly to confirm the acute observation 
