444 
GEOLOGY OF THE FOURTH DISTRICT. 
ported by a gentle current over the bottom of the ancient lake, which might move sand; 
while clay, if once deposited, would be less easily disturbed. 
The soil upon the mountain ridge is sand, or sandy loam, for a mile or two south, when 
the proportion of clay increases. Along the Tonnewanda, clay soil predominates, owing to 
the gypseous marls, which are argillaceous, in the lower part of the formation. These marls 
extend into Niagara county, their outcrop being a little distance north of the Tonawanda creek. 
Clays. 
Beds of clay are found in every town in Niagara county, though many are of impure quality 
from admixture of sand and carbonate of lime. The demand for bricks has, however, been 
confined to one or two points, and consequently these beds have not been explored. The 
prevalence of limestone, and limestone shale, more or less affects all the deposits of clay, 
except those along the lake shore. 
Many of the bricks manufactured in the county are of inferior quality, arising from the 
use of sandy loam mixed with the clay, instead of a pure siliceous sand. This loam contains 
abundance of fine particles of limestone, and when burned, becomes lime: the action of water 
on such bricks is rapidly destructive. 
On the lake shore, a bed of clay continues almost from the eastern to the western extremity 
of the county. In some places this thins out, and its place is occupied by gravel or loam, and 
sometimes the clay is intermixed with one or both these substances ; the upper part being 
grey and less pure than the lower, which is usually of a bluish color throughout, or variega¬ 
ted with spots of brown and green. Where the lower part of the stratum is seen, it rests on 
a partially indurated deposit of gravel and clay, of a reddish color, and this rests upon the red 
marl or sandstone. The clay is from two to six feet thick, and often contains pebbles and 
boulders, similar to those on the lake shore. Frequently we observe alternations of the clay 
and a part of the gravel stratum below and above, and the clay is often much bent and con¬ 
torted, although it rests on a nearly horizontal base. These alternations and contortions are 
in many places very remarkable, and would induce the belief that almost any position, observed 
in stratified rocks, may be given during their deposition. The presence of pebbles and boul¬ 
ders in the clay, proves that the water from which it was deposited had sufficient velocity 
to transport large and heavy materials. 
The grey loamy clay above the blue clay sometimes attains the thickness of four or five 
feet, and in some places the whole deposit is of this color. The grey, where it occurs, appears 
entirely distinct from the blue, as if it might have been deposited at a subsequent period. In 
this clay we find the calcareous concretions called clay stones, or “ clay dogs,” which assume 
all imaginary forms, sometimes the most fantastic. They are often spherical, and sometimes 
two or more of them attached together. They appear at regular intervals in the strata, and 
commonly aline of them marks the junction of the grey with the blue clay below, being at that 
point where the surface water meets an impervious layer. These substances are an earthy 
carbonate of lime, which is apparently deposited from the water precolating from the surface. 
