1893. ] NEW YORK ACADEMY OF SCIENCES. 103 
with a little mica, and varying quantities of ferric oxide, The 
latter is sometimes so abundant that that the rock has been 
mined as an iron ore, 
Where much folded, the sandstone often has the appearance 
of a breccia, made up of thin, angular fragments. On close 
examination, these fragments prove to be bits of sandstone, and 
the brecciated character is seen to be due to a shattering of the 
rock by pressure, as stated by Emmons*. It is easy to find 
every stage between the unchanged rock and that which has 
been reduced to small fragments, recemented by subsequent 
infiltration. 
Comparing this result of pressure with that produced by the 
same cause in the limestone, a marked contrast is presented, 
In the sandstone the effect is largely mechanical—a breaking 
of the rock. In the limestone, chemical changes and crystal- 
lization are the prominent result. 
Crossbedding on a large scale is very conspicuous in the 
sandstone, often obscuring the true dip, Concretions also are 
abundant in some localities, two apparently distinct kinds being 
found—small spherical and large cylindrical. The former have 
been mentioned by Brooks}, the latter by Hough}. The small 
concretions resemble closely those that are found in many other 
formations, but the large ones are peculiar, Of cylindrical 
form, one to twenty feet in diameter, and perhaps six feet, they 
usually stand perpendicular to the bedding, and their appear- 
ance is striking. The material of the concretions does not 
differ from that of the surrounding rock, and the causes are 
obscure, which explain why it should be arranged as it is, in 
successive layers, concentric about a line. The age of the 
sandstone was stated by Emmons to be Potsdam, and such it 
has been always considered by later writers. Though no fossils 
have been found in this immediate vicinity, there seems to be 
no reason for doubting the correctness of this view. 
Relation of Sandstone to Limestone.—There is some confusion 
in Emmons’ discussion of the relation between the sandstone 
and the limestone. He classes the limestone as primitive and 
yet plainly implies that it is younger than the sandstone. For 
he describes disturbance and contact metamorphism in the 
sandstone produced by the supposed intrusion of igneous 
* Geology of New York, 2d District, page 104. 
+ American Journal of Science, iii., IV., p. 25. 
+ Hough, F.B., 3d Ann. Rept. Regts. Univ. N. Y., p. 32; also Amer. Associa- 
tion Proce. LY., p. 362. 
