464 
GEOLOGY OF THE FOURTH DISTRICT. 
ing appearance. The surface covered is several acres, and the clay is piled up in little 
mounds and hillocks, with depressions between them, much in the same manner as the drift 
hills of Ontario, and other parts of the district. Over a great portion of this surface no trees 
are growing, and in some places even grass scarcely grows upon the clayey slopes. On the 
opposite side of the river there is evidence of a former slide, even much more extensive than 
this one, but the uneven surface has become overgrown with a heavy forest. The Gardeau 
slide carried an immense body of earth into the Genesee river, which changed the direction 
of the channel to the other side of the valley. These slides are but miniatures of those which 
occur in the high primary mountains of the northern part of the State. 
GENESEE COUNTY. 
In this county we find the same rocks as in Livingston, with the addition of the Onondaga salt 
group on the north, which extends through the towns of Bergen, Byron, Elba and Alabama, 
and into the northern parts of Leroy and Stafford. 
The most northern portions of this mass consist of greyish or greenish-grey marl, homoge¬ 
neous in texture, and very compact when first exposed, but crumbling rapidly. Thin courses 
of reddish and chocolate-colored marl are seen in some places in the northern part of the 
county. Farther south, and along the centre of these towns, it is more grey or ash-colored, 
contains thin seams of fibrous gypsum and selenite, and occasionally small masses of granular 
gypsum. This part of the mass is exposed only in wells, which, from the difficulty in obtain¬ 
ing water, are often dug to the depth of seventy or eighty feet. The grey marl and gypsum 
is found to contain large seams or joints apparently water-worn ; these without doubt act as 
drains, and carry off the water from above. 
Some wells ill this part of the group yield an acid water. One of these, belonging to Mr. 
Gifford, of Bergen, I examined; the water is said to contain acid enough to curdle milk ; 
and though not sensible to the taste, is considered unfit for use. The famed acid spring in 
Byron rises from this rock. Some of the wells in the immediate vicinity, and in the same 
formation, yield good water. 
A little north of Bergen centre the greenish marl comes to the surface, and is excavated 
for the passage of the railroad. Two miles west of that place, the same marl is seen in the 
roads and in the banks of the small streams, and approaches the surface over the greater 
part of this neighborhood. 
The grey or ash-colored marls just described, are succeeded by bluish, slaty and drab colored 
impure limestones, which embrace large beds of gypsum. These occur mostly in the north 
part of Leroy and Stafford. Gypsum is also found in the western part of Elba, near the 
junction of the Pine-hill road with the Batavia and Lockport turnpike, which is the most 
