No. 275. J 
291 
county, is occupied by the " saliferous group of Onondaga." Nearly all 
this northern part of the county is deeply covered with alluvium; and 
the rocks appear at very few points. One of these is in the bank of 
Bear creek, where gypsum was quarried many years since, and another 
about three miles north of Seneca falls, where gypsum and gypseous 
marl were penetrated in digging a well. 
The great depth at which gypsum is found in the north part of the 
county will, for the present, and for a long time to come, preclude its 
profitable exploration. The waters of Seneca lake, which have worn a 
recent outlet along the southern limit of this series, expose the gypsum 
and associated rocks near Seneca falls village, and for nearly three miles 
below. Along this distance the gypsum is extensively quarried. It 
occurs in irregular, often conical masses, enclosed in a grayish friable 
marl, with which it is often much intermixed, and in consequence dete- 
riorated in quality. 
There is here no evidence that the masses of gypsum have forced up 
the strata, as noticed in some places in Monroe and Ontario counties. 
On the other hand the lines of stratification in the marl are continued 
through the mass of gypsum without interruption. The strata are un- 
dulated; the depressions being between the beds of gypsum; and this 
appearance may have been caused either from the porous nature of the 
marl by which some of it has been dissolved and carried off, or from 
contraction, on drying of the mass between the gypsum beds. The lat- 
ter being a chemical compound, and the force of aggregation greater, on 
becoming indurated, has contracted less than the surrounding marl; it 
consequently presents a slight convexity in the surface. In these beds 
all appearances prove that the gypsum was separated from the marl by 
chemical attraction, while each was in a fluid or semifluid state. Small 
particles and seams of gypsum still remain scattered through the sur- 
rounding mass, and it very appropriately receives the name of gypseous 
marl. 
The rocks belonging to this formation, were described in the report of 
last year; they all bear much uniformity in character at different points, 
and are easily recognized even when the gypsum is not present, by their 
argillaceous nature, and nearly uniform drab or ash colour on exposure to 
weather. Some portions are harder and darker; frequently green on first 
exposure. Owing to the usually soft nature of the strata, they have 
been removed from extensive tracts, and the space filled with alluvium 
from more northern rocks; this is particularly the case in Wayne, and 
