38 
GEOLOGY OF THE FOURTH DISTRICT. 
This rock is extensively quarried for flagging stones a mile north of Lockport, where slabs 
of the finest quality, and of any dimensions, are obtained. The surfaces are almost entirely 
smooth, interrupted only by the slight wave-lines ; they can be obtained of any desirable thick¬ 
ness, and from their uniform quartzose character, are extremely durable, and wear evenly. 
These quarries are owned by Whitmore & Co. 
Some quarries in this rock have more recently been opened near Medina, where stone of 
similar character is obtained; and when a sufficient demand for the article shall be created, 
the whole distance from Medina to Lockport, along the outcrop, can be converted to an open 
quarry. At Lewiston, where the rock has been excavated, it does not furnish so good flagging 
stones, the layers being thicker, and better suited for building. Other localities in the neigh¬ 
borhood may, however, prove of a different character. 
3. Red Shale and Sandstone. 
The grey quartzose sandstone is succeeded by a red shaly or marly mass, similar to that 
below, which soon alternates with thin courses of red argillaceous or quartzose sandstone. 
The shaly matter diminishes, and the sandstone increases in the same ratio as we ascend, and 
towards the top becomes mingled with grey or greenish grey in large proportion. The whole 
is finally terminated by a grey or ash-colored siliceous, or, in some places, argillaceous sand¬ 
stone, differing but slightly from that below. 
This division of the rock is mottled or variegated with spots and lines of grey and green; 
these are often circular, presenting the same structure and composition as the mass around. 
The difference of color is owing to a change in the oxidation of the iron, which is the coloring 
principle of the rock, and has been produced by some carbonaceous or bituminous substance 
lodged at a point now the centre of the green spot. Bands of green, parallel to the stratification, 
have been produced in the same manner, the carbonaceous matter spreading over a considerable 
surface. Lines of green perpendicular to the stratification, which frequently occur, are not 
so readily explained upon any supposition of this kind, and I am inclined to believe that they 
have been produced by the infiltration of water charged with carbonaceous matter from the 
soil above. That water may produce such discoloration, I have observed many facts to cor¬ 
roborate ; and if the change in color can be produced by a small quantity of bituminous or 
carbonaceous matter, for some distance around it, I see no reason why the same change may 
not be produced by water flowing through peaty soils, and passing into a seam or joint in the 
rock. I have seen pebbles of the same red rock of the more sandy variety, which had lain in 
the bed of a muck swamp, with the color completely discharged from the outer part. The 
color is likewise lost by continued heat, as is proved in stones used in the furnace at Wolcott. 
The presence of carbon, in this instance, may have aided to produce the change. 
