LIVINGSTON COUNTV. 
403 
the water leaps a hundred feet from the top of this rock. It underlies the village of Geneseo, 
and is seen in many places on the road east from that place, and in the ravines between it and 
Conesus lake. In this neighborhood the black shale is succeeded by a thin stratum of impure 
limestone, which has been burned for lime at one place near Moscow. 
At the bridge crossing the Genesee near Mount-Morris, the Genesee slate is exposed, pos¬ 
sessing all its essential characters ; being bituminous, containing thin seams of coal, great 
numbers of septaria, sometimes irregularly scattered, at other times in regular courses. 
The arrangement and distribution of these septaria depended upon the supply of material ; 
and the tendency to concretionary forms proceeded from the amount of material being too 
small for a continuous stratum, which, together with the homogeneous state of the particles, 
caused them to take this form. Sometimes we see a single insulated mass, and no others in 
the same parallel of stratification; at other times we find them distant from each other, but in 
the same plane of stratification. Again we may find a course of them in the same plane, and each 
of them separated only a few feet from the other. Still again when the supply was greater, we 
find a continuous stratum or bed, as in the case on Seneca lake, where the regular course of 
septaria in the upper part of the black shale becomes, from increase of material, a continuous 
stratum three or four feet in thickness. This change is seen in many cases near the thinning 
out of a mass; the supply of matter diminishing, till it is-traced only by distant nodules or 
concretions. 
The Cashaqua shale, for one hundred feet in thickness, is exhibited at the gorge at Mount- 
Morris, limited below by the Genesee slate, and above by the Gardeau flagstones. It also ap¬ 
pears in many ravines in the south and southwest part of Leicester ; in the vicinity of Mount- 
Morris ; in the Cashaqua creek, whence it takes its name; in the ravines on the east of the 
valley, and at a higher elevation southeast from Geneseo and approaching nearly to the 
village. 
The Gardeau and Portage rocks already described, are the southern rocks of the county. 
These are seen in the deep gorge of the Genesee, and in almost all the ravines and water 
courses of the southern towns. Among numerous localities as we approach Dansville, may 
be mentioned Stony brook in Sparta, where several hundred feet of these rocks are exposed. 
The shale in the upper part of this ravine has been ground and used as plaster. 
There are several quarries between this place and Dansville, in which it is difficult to find 
any characteristic fossils. The rocks consist of thick layers of sandstone, with intervening 
masses of shale; and near Dansville, give more marked evidence of the group to which they 
belong. Quarries have been opened on both sides of the valley, where materials were 
obtained for locks, bridges, etc. on the Genesee valley canal. This group also affords the 
finest flagging stones in the district; these are known by the presence of the fucoids already 
mentioned. 
The great marl deposit of Wheatland extends into the northern margin of this county ; 
there is also an extensive deposit of marl about one mile east of Caledonia. 
The Gardeau slide, which occurred more than thirty years since, still presents an interest- 
