MEDINA SANDSTONE. 
35 
and also from the fact that it appears on the north side of the lake to the west of Toronto. 
It continues beyond the Niagara river, having been traced as far as the head of Lake Ontario, 
and it is believed to extend much farther westward. 
In Wayne county, it is usually a firm siliceous rock, approaching to a conglomerate in some 
places near the lake level. On going westward, the sand in part gives place to argillaceous 
matter ; and before reaching the Genesee, the greater part of the mass, visible above the lake, 
has become a marly sandstone; the upper part, only, being firm, and withstanding the effects 
of weathering. Its enduring character in the eastern part of the district is well exhibited by 
the great number of pebbles and boulders scattered over the surface of Wayne county, and 
some parts of Monroe, and which diminish westward. Pebbles of this rock, however, form 
a large portion of the drift far to the south, and may be found intermingled with the products 
of more southern ranges, in all the valleys as far as the Pennsylvania line. In some places 
in the northern range of counties of the district, the surface is literally covered with pebbles 
of this rock, almost wholly unmixed with any other. 
From its shaly or marly character upon the Genesee river and in the country west, this rock 
was originally mistaken for the red shale of the Salt group, which it closely resembles. The 
latter appears in Onondaga county on the canal; and by following the same line westward, 
no other rock appears until within a short, distance of Rochester. The marly sandstone ap¬ 
pearing here was naturally taken for a continuation of the rock seen in the vicinity of Syracuse, 
and the occurrence of salt springs likewise aided to complete the deception. This opinion 
prevailed until the Geological survey had made some progress, when it was found that the 
Clinton and Niagara groups both intervened between the Medina sandstone and the continua¬ 
tion of the Onondaga-salt group. 
The scenery exhibited along the line of outcrop of this rock is in some places interesting in 
the highest degree. In Wayne county, from its rising but little above the lake, it forms only 
some inconsiderable falls in the streams; always strongly contrasting, by its deep reddish 
brown color, with the rocks above. In Monroe county, it forms the lower falls of the Gene¬ 
see, one hundred and ten feet in height; one of the most picturesque spots in the district, 
exhibiting not only this rock, but above it, in the cliff, the Clinton group and shale of the Nia¬ 
gara. It also forms the banks of the river below, extending nearly to the lake. In Orleans 
county, at Albion, there is a low fall on Sandy creek over the same sandstone ; and by fol¬ 
lowing that stream farther up, its connection with the higher rocks can be readily observed. 
At Medina, on Oak-orchard creek, this rock forms the beautiful little cascade represented in 
the woodcut. 
The deep gorge, and the high cliffs on either side of the Niagara at Lewiston, are more than 
half excavated in this rock ; and the partial obstruction of the water at the whirlpool is caused 
by a part of the same mass. Its alternations of harder and softer masses produce cliffs or 
cascades along its whole extent. 
This rock, where best developed, admits of a fourfold division, as it appears throughout the 
greater part of the Fourth district. Including the “Grey band,” which here forms an integral 
part of the mass, it may be represented as follows : 
