SUPERFICIAL DETRITUS. 
323 
following section, about seventy miles farther west, illustrates the same position, though the 
conditions seem not to have been as equal throughout as in the first. 
159. 
Section of the bank of Lake Ontario, town of Wilson, Niagara county. 
4. The soil of clayey loam, with clay helotv. 
3. Gravel, clay and sand, of the neighboring rocks, folding over and passing beneath No. 2. 
2. Blue clay and gravel. The pebbles are principally of the rocks of the Hudson river group. 
1. Red clay and gravel of the Medina sandstone. 
The clay deposit of the surface is often succeeded by sand and sandy loam, as in Monroe 
county; and this sometimes rests upon the gravel, without the intervention of clay. 
In most instances, there is evidence of the most perfect uniformity in the production of these 
deposits ; and when they can be traced over so large an area, it is plain that the few apparent 
exceptions will be met by some other explanation. As before remarked, where these ac¬ 
cumulations form hills and ridges, they do not always preserve the same regularity as in the 
widely distributed and more shallow deposits. This may have resulted, in some instances, 
from subsequent causes, or from the force of contending currents while the ocean covered the 
surface. In many instances, the sand is irregularly deposited; and at others, there appear 
to have been partial depositions and denudations during the period of its formation. 
The following is a sketch by the late Dr. G. W. Boyd, of a hill about two miles east of 
Rochester. The ridge has been excavated in an east and west direction, for the passage of a 
road, presenting a depth of thirty feet or more. 
160. 
1 & 2. Deposits of fine sand variously inclined, with a few layers of gravel. 
3. Coarse giave), with large boulders of limestone. 
4. A subsequent deposit of sand, like Nos. 1 and 2, 
41* 
