MEDINA SANDSTONE. 43 
The rock again appears near Holley, and at numerous places on the Erie canal westward. 
It is well exposed in the small stream on the south side of the canal near Albion, and is seen 
more or less between this place and Medina. 
At Medina, on the Oak-orchard creek, we have the best exposure of the mass, which exists 
in the State, and hence its name. The thickness here exposed is not greater than on the 
Genesee river, nor so great as on the Niagara at Lewiston, but it exhibits all its fossil types 
in the greatest perfection. 
A little northwest of the village, it is quarried for flagging stones. From Medina westward 
it is almost constantly to be observed either in the canal, or in the terrace formed by the out¬ 
cropping edge of the middle division as far as Lockport. At this place it is well exposed 
about a mile below the village, on Eighteen-mile creek, exhibiting likewise its fossil shells, 
though in less profusion than at Medina. The Fucoides Harlani, however, is rare, and not 
well preserved here. In the quarries, and the brow of the hill further north, the central portion 
of the mass is well exposed. 
From Lockport westward, the Third and Fourth divisions form part of the slope of the 
terrace, contributing to the height of the same above the country on the north. The central 
hard portion being less destructible, has protected the base of the terrace, and projects be¬ 
yond the higher part in a step or table. 
In the banks of the Niagara, it is very finely exposed. At Lewiston, it exhibits about two 
hundred feet in thickness, and gradually declining, passes beneath the water before reaching 
the falls. The grey quartzose sandstone, like that at Lockport and Medina, is seen at the 
Whirlpool, projecting into the river on either side, and forming a barrier which has at one 
period obstructed the waters in their passage to the lake. Below Lewiston it is seen in the 
banks of the river, extending nearly to the lake shore, where it slopes down, and becomes 
covered by the superincumbent clay. 
On the Welland canal, at St. Catharines, at Hamilton, and numerous other places along 
the slope of the terrace, this rock may be seen, showing its continuation beyond New-York, 
and in the same line of direction. 
Thickness. — From the circumstance that the base of this rock is nowhere to be seen in 
the Fourth district, its entire thickness cannot be ascertained. Its greatest width is on the 
Niagara river; but here a large portion of it is excavated on the north, leaving probably less 
than half its original extent within the State. From the width here exposed, the thickness 
actually measured, and the rate of dip to the southward, there is about three hundred and fifty 
feet of the rock between the mouth of Niagara river and the termination of the rock above 
Lewiston. By reference to the Geological map, it will be seen that this rock thins out en¬ 
tirely in an easterly direction in Oneida county; showing from that point westerly as far as 
Lake Ontario, a gradual increase in thickness. Examinations farther westward are required 
before the point of its greatest development can be ascertained. 
