368 
GEOLOGY OF THE FIRST DISTRICT. 
In the Fourth Annual Geological Report of New-York, this series of rocks, under the 
name of the Hudson slate group, was briefly described as an alteration of the shales, slates 
and limestones, with siliceous and calcareous breccias ; and as underlying unconformably, 
with a few exceptions, the superincumbent rocks. This is true in the immediate valley of the 
Hudson, and westward to the great line of fracture. Beyond that, to the west, the superin¬ 
cumbent rocks overlie this series conformably. 
This is an important fact, inasmuch as it demonstrates the geological period of this, as one 
of the several upheaving actions that have broken up and deranged the position of the pre¬ 
existing strata. 
The Helderberg limestone series at Becraft’s mountain. Pine mountain, Wilbur, and many 
other localities, in a position nearly horizontal, overlies unconformably the highly inclined 
subjacent rocks ; while in the Mohawk valley, and generally west of the great fracture, they 
are nearly horizontal and conformable. Other elevatory movements have occurred since the 
deposition of the superior rocks, by which they have partaken of the general movement, been 
broken, contorted, upheaved, and even overturned in some localities, so as to invert the origi¬ 
nal order of superposition. 
It has been observed that some of the rocks in the valley of the Hudson, which lie at a 
high angle of inclination, and dip in the same direction as the proper slates of the Hudson 
rocks, are similar, and it is believed identical with the Shawangunk grit, and the masses 
superposed upon it.* 
Topographical and agricultural characters. 
The agricultural character of a district is dependent on the rocky masses under the soil, 
their stratification, the materials of which the soil is composed, and the topographical charac¬ 
ter of the country. 
The two first of these points may be illustrated in the district under examination in this 
report, by calling the attention of the reader to those portions of Schenectady county, and to 
Rensselaer, Washington and other counties, that have the Hudson slate rocks beneath their 
soils, and that lie higher in level than the ancient alluvion of clay and sand of the Hudson 
river valley. These rocks are alternations of slates, with slaty and fine grained sandstones, 
and hard grit rocks. The strata of slate, and many of those of the other rocks, are nearly 
or quite impervious to water. In Schenectady county, the strata of these rocks lie nearly 
horizontal, are impervious to water, and by decomposition form a highly argillaceous soil. 
The consequence is, that the hill lands are generally cold and wet soils. In portions of the 
* A rock that bears some resemblance to the Shawangunk grit, ranges through the county of Rensselaer and northern part of 
Columbia, forming a part of Petersburgh mountain in the former, and the high range of land west of Lebanon valley in the latter 
county. It is a greenish and bluish hard siliceous grit, sometimes granular, sometimes brecciated, and at others a conglomerate 
or puddingstone. Itcontains no organic remains as far as isyet known, and it has been applied to no use except as a rough wall 
stone. The same rock, with some modifications, ranges through a part of Dutchess, Orange and Ulster counties. 
