122 
GEOLOGY OF THE FOURTH DISTRICT. 
appearing in the banks of the outlet, though it is known to exist farther north. On the south 
side of the outlet, there are several beds worked near the stream. The higher groups of the 
Water-lime and the succeeding limestones limit the extent of this deposit within a distance of 
half a mile to a mile south of the outlet. Few beds have been opened west of this town along 
the outlet, though several are exposed. The principal beds in this neighborhood, are those 
of Mr. Hildreth, on the south side ; Norton & Co., Vandemark & Co., Cook, Robinson and 
Vanderhoff, on the north side. 
Some of these quarries present interesting features not noticed elsewhere. The following 
illustration is of Norton & Co.’s quarry, and Vandemark’s presents nearly the same appearance. 
46 . 
a. a. A thin stratum of tough si'.ico-argillaceous limestone, extending through the plaster beds, and continuously through 
the adjoining rock. 
b. Soft shale or marl, filling the spaces between the beds of gypsum. 
c. Two feet of compact, and slaty limestone, the harder portions with irregular cavities. 
d. Six feet soft greenish shale. 
The continuation of the impure stratum of limestone through the beds of gypsum, renders 
this an interesting exposure. The beds are likewise divided in the same way by a layer of 
slaty limestone at the line represented as the base of this diagram, and below this the gypsum 
continues to the depth of seven feet. These occurrences prove the manner in which this mi¬ 
neral has been segregated from the surrounding rock. The softer portions of the marl readily 
gave way for the formation of these masses, which were more strongly attracted together ; on 
the other hand, the shaly siliceous mass, which continues through the beds, seems to have 
possessed attractive force equally with the particles of gypsum, thus maintaining its position 
while the softer portions were displaced. 
Almost all the gypsum effervesces with acids, showing the presence of carbonate of lime, 
and its dull earthy color is owing to admixture of argillaceous matter. The beds of gypsum 
are usually horizontal at the base, resting on the same kind of marly deposit as that above. 
In a few instances, the base is irregular or undulating, resting on an uneven bed. The illus¬ 
tration No. 47 presents an example of this kind, where the marl rises above, and the base is 
partially enclosed in the gypsum. 
