306 
[Assembly 
the marl pass through the beds of gypsum, and in several instances 
where one or two thin courses of hard argillaceous limestone occcur in 
the former, these also are continued through the latter, the intervention 
of the rock merely breaking the continuity of the plaster without other- 
wise affecting it. In this series, the force of agpjregation or chemical 
attraction seems not to have been sufficiently powerful to separate the 
gypsum from all surrounding materials; consequently we find it much 
intermixed with the marl, and wherever the attraction of particles was 
stronger than in either of these, as in the limestone, the strata continued 
their course through the mass, scarcely interrupted at all. The greater 
tenacity of the latter may have prevented the mobility necessary to an 
entire separation of particles, and from this cause in part may arise the 
admixture of substances. 
The course of the Canandaigua outlet, from Manchester village to 
near Vienna, is along the line of the Saliferous group and water lime, 
leaving the latter entirely on the south, and the former, with the excep- 
tion of a few beds, on the north. East of Vienna, all the marl and 
gypsum has been removed, and is replaced by a deep deposit of sandy 
alluvium; in the west of Manchester, the same circumstance is observ- 
ed, and on the north side of the outlet, instead of the gypsum, we find 
alluvial hills rising eighty or one hundred feet above the valley, but not 
appearing south of the stream. From Manchester to the west line of 
the county, a low valley extends along the southern boundary of the 
gypseous rocks, with alluvial hills rising on its northern side. The ori- 
ginal course of the Canandaigua outlet appears to have been north; and 
it is very evident from the character of the rocks along which it passes, 
after turning east, that this portion at least was excavated recently, or 
long after the deposition of the alluvium, which may have closed its 
northern egress. 
The principal quarries of gypsum are those of Robinson, Korton & 
Co., Cook, Vandermark & Co., and Hildreth. From these, about six 
thousand ions annually are ground at the mills on the outlet, and sold 
within the county. The supply is sufficient for a much greater amount, 
and unless the demand increases, the quarries will not be exhausted in 
many years. Whenever this happens, explorations will extend north 
of the present quarries; and in all the valleys along the north part of 
the county, the middle series of plaster beds will probably be found. 
The water limes are better developed in this county than in Seneca, 
appearing in their characteristic drab colour. The mass may be traced 
