No. 161.] 
179 
Gypsum, 
Numerous beds of gypsum occur in the counties of Madison, On- 
ondaga and Seneca, and generally bordering the salt region. This 
mineral occurs in irregular somewhat conical masses, imbedded in 
gypseous marl, rarely as much as twenty-five feet in diameter at 
base, and from ten to thirty feet deep. In consequence of this ma- 
terial having been derived from the surrounding rocks, by the lo- 
cal action of chemical agents with varying degrees of intensity, we 
find the gypsum never occurring in parallel layers, or to a conside- 
rable uninterrupted extent, and it varies greatly in external cha- 
racter and purity of composition. In dry and elevated situations, 
as in the hills, it is crystalline and semitransparent, and is highly 
esteemed as a stimulant to vegetation. A black, opake variety oc- 
curs in masses, mixed with clay and other impurities, and is not so 
much valued as the preceding. It is found in low, wet situations, 
and bears the local name of Swamp plaster. 
Hydraulic Limestone. 
We visited extensive quarries of this limestone in the counties 
of Madison and Onondaga, where it is quarried and burned into 
water lime, as at Chittenango, Fayetteville, &c. This rock is 
abundant in all the region which contains gypsum, and occurs in 
immediate vicinity to the latter mineral. It appears at a higher 
level than gypsum, and generally alternates with the lower beds 
of a blue limestone series; thus, commencing below with the gyp- 
seous beds, we find the water limestone first above them, alternat- 
ing with the blue for a certain extent, then layers of blue and 
gray lime in succession. Water limestone is a compact gray rock, 
forming regular layers of several feet in thickness, and is properly 
an argillo- ferruginous limestone. The iron and argil appear to be 
ingredients essential to those peculiar properties of the lime ob- 
tained from it by burning. 
We noticed some solid masses of artificial stone which were 
made of water cement, and intended for door steps, and was also 
informed that a dwelling house in Schenectady has been entirely 
constructed of this material. 
Calcareous Tufa. 
Derived from the strata. of this series, particularly those which 
contain gypsum, are considerable deposites of tufa and marl. 
These are a recent deposition from calcareous waters, and contain 
