454 ELEMENTARY GEOLOGY 
are probably similar to those of other parts of the coun- 
try, and of other ages; but they have been worked out 
so satisfactorily that they serve as a better illustration 
than any other district which we know in America. 
The state of New York during the Silurian was 
occupied by sea, excepting in the eastern part along 
the bases of the mountains that were developed at the 
close of the Ordovician, and also in the Adirondack 
region, which rose out of the sea as a mountainous mass. 
The coast-line of this sea was therefore in the eastern 
part of the state, and the waters deepened toward the 
west. Therefore, since sediments are coarser near the 
shore than at a distance from it, the rocks of this age 
vary in coarseness from the shore into the deeper parts 
in the western portion of the state. 
The lower strata of the Silurian (known as the Oneida) are 
conglomerates in the east, grading to sandstone in the west 
(known in New York as Medina sandstone), and beyond this to 
shales. The conglomerate represents the ancient beach along 
the shores of the inland sea. At present it is found extending 
throughout the folds of the Appalachians, into which it has been 
built by mountain formation of a later period; for the site of the 
Appalachians was still sea during the Silurian time. Because of 
its great strength in resisting denudation, this consolidated beach, 
composed of quartz and other pebbles, cemented in a matrix of 
sand, now rises to form the crests of many of the Appalachian 
ranges. The conglomerate bed reaches the thickness of from five 
to eight hundred feet. 
Above the Medina sandstone group is found a series 08 shale 
and limestone, known as the Clinton group in New York. These 
a 
