ONTARIO COUNTY. 
453 
The principal building materials are the Corniferous limestone in the north, and the thin- 
bedded sandstone in the south part of the county. 
Calcareous tufa and marl occur in small quantities in several places; but from the nar¬ 
rowness of the county, descending on either side to the lake shores, there are few situations 
admitting of large accumulations. The most extensive which I have seen, is on the farm of 
Mr. Dunlap, near the village of Ovid. 
This county possesses few mineral resources except gypsum, being eminently agricultural 
with a highly fertile soil. The northwestern portion is somewhat sandy, becoming loamy on 
the south side of the outlet, while some portions east of this are quite clayey. The prevail¬ 
ing soil of the higher parts of the county is a clayey gravel. 
Northern boulders are rare in this county, though the rocks of the northern part of the 
district are largely intermixed in the soil. 
ONTARIO COUNTY. 
In this county we find the same rocks, and in the same general order, as in Seneca. The 
“ Saliferous Group of Onondaga ” occupies that part of the county which lies north of a line 
drawn from a point one mile north of Oak’s corners, in the town of Phelps, along the course 
of the Canandaigua outlet to Manchester, and thence west to Victor. The vast accumulation 
of drift, however, leaves the rocks exposed but at few points, which are mostly along streams. 
In a few cases, what appear externally to be drift hills are isolated masses of gypseous marl, 
etc. deeply covered; and in some instances small masses of gypsum have been found in these, 
much above the ordinary level of the valleys and surrounding country. Admitting that the 
gypseous rocks originally held a higher elevation, and equal to that of the drift hills, before 
the intermediate portions were transported southward, the fact proves the vast quantity of 
matter removed by this agency. 
This group of rocks is much better exhibited in Ontario than in Seneca county, having a 
greater extent, and in one or two places developing a different character. The gypsum here 
occupies three distinct ranges ; the northern or lowest appearing upon, or just north of the 
county line, and the other two within the county. In the first the gypsum is associated with 
a grey marl, which reposes on a green marl containing no gypsum. The grey marl exhibits 
iron stains and decomposing pyrites ; and pyrites is also found with the plaster which occurs 
in small irregular masses, having a granular or crystalline texture, and frequently accompanied 
by selenite. Masses of selenite are very abundant in the marl, varying from the size of a 
walnut to several pounds weight, isolated as regards themselves, and having no connection 
whatever with the larger masses of gypsum. In appearance and mode of formation they are 
very analogous to those found in the Tertiary clays. The limpid selenite often embraces a small 
