ONONDAGA SALT GROUP. 
123 
The strata are slightly undulated, always rising gently towards the mass and descending 
from it. This is doubtless caused by the nature of the two substances and their comparative 
power of resisting atmospheric and other agencies. The gypsum is compact and little affected 
by air or moisture, while the numerous seams of the surrounding marly and shaly mass 
freely admit water, which, from the soft and yielding nature of the rock, gradually removes 
portions which are carried off in the outlet of the springs and streams, thus diminishing the 
quantity, and causing a slight sinking down between the beds. The illustration No. 48 
exhibits the usual appearance of the strata in these situations. 
48 
The enclosed bed of gypsum exhibits a more continuous character than usual, presenting 
three conical or dome-shaped elevations, separated by the nearly horizontally stratified marl. 
The lower range of beds, as seen in Monroe county, are nowhere known in this part of the 
country. At Seneca falls the soft marls are succeeded above by some harder layers of im¬ 
pure limestone, with irregular cavities which are lined with calcareous matter, in mammillary 
forms, evidently a recent deposition from solution. Connected with these strata, and just 
below, are some small masses of dark colored, crystallized gypsum, in stellated forms. 
These porous layers are succeeded by a darker and more pure, compact, brittle, limestone, 
which is the highest rock visible at this place. This would appear to be the terminal deposit 
16* 
