78 TJic American Geologist. Fisbnuiry, i898 
crn flank of the Archaean mass. The main argument for this 
supposition is that the Potsdam, Calciferous, Trenton and 
Utica formations, are developed here in a like manner as the 
respective strata which, in the south, strike continuously along 
the foot of the Adirondack's. The Potsdam — consisting of a 
rusty weathering, not very coarse grained, somewhat calcare- 
ous sandstone, that alternates with lighter colored beds— and 
the light-colored arenaceous limestone that represents the Cal- 
ciferous, differ in no way from the outcrops in the Mohawk 
valley. The Utica shale, which is well exposed in a pit for 
breaking road-metal, and which outcrops in a neighboring 
rivulet in several places, is the typical, fine-grained, often 
fissile black shale of the lower part of the formation and con- 
tains scattered specimens of Diplograptus foliaceus Murch. 
(= pristis Hall). A slab in the ravine contained a greater 
number of these graptolites, which were arranged between 
N 50 degrees E and N 90 degrees E. In slabs found on a 
road, fragments of Endoceras and casts, probably belonging 
to a Modiolopsis, were met with. Neither does the light-gray, 
highly fossiliferous limestone, Vv^hich, for many years, has been 
used for lime-burning, differ from the Trenton in the Mohawk 
valley. The only remarkable feature is a bed which contains 
round pebbles of a few inches diameter, and which are derived 
from a lower part of the limestone. But such conglomerates 
occur even much farther south in the Trenton. They are of 
general interest, as the Trenton limestone has. been often 
regarded,* and not without good reason, as a deep-water de- 
posit. A very interesting occurrence of conglomerate in the 
Trenton was found by the writer at Ingham's Mills, on East 
Canada creek, in an exposure, which has been made known 
by N. H. Darton.t 
The slaty intercalation in the upper eight feet of thin- 
bedded limestone, near the top of the section, was here found 
to contain water-worn, rounded, flat boulders,^ which reach a 
diameter of several feet and are derived from the light-colored 
compact layers below the typical Birdseye limestone. As the 
*Compare for instance Lapworth, Trans. Roy. Soc. Can. for 1886, 
V, Sec. IV, p. 176. 
tGeology of the Mohawk Valley, Rept. of N. Y. State Geologist 
for 1893, p. 422. 
JSee Plate IX, tig. 2. 
