130 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
have been utilized. The top clay is said to make very good brick, 
which are used for building in Canonsburg. 
This clay occurs at several points in the quadrangle, but is of very 
local occurrence. It may be present on any of the rock benches in 
the valley of Tenmile Creek and elsewhere, but the patches are prob- 
ably too local, thin, and gravelly to be of any importance in this area. 
SHALE. 
Shales of fine texture are very abundant in the Dunkard group and 
outcrop over wide areas. In other parts of the country some of these 
shales have been widely used in the manufacture of brick. In the 
Amity quadrangle and as a rule in western Pennsylvania they have 
been little used, but seem to offer a source of supply suitable for brick- 
making, and perhaps also in connection with limestone for making 
cement. 
At only two points in the quadrangle is shale known to have been 
utilized. One of these is in the southern part of the borough of Wash- 
ington, near the Baltimore and Ohio Railroad, where the Donley 
Brick Company operates a small plant for the manufacture of red 
brick. Shale is here worked in an open cut 25 feet deep, and it is said 
that an even greater thickness of the rock is suitable for the purpose. 
The shale is used just as it comes from the bank and is manufactured 
by the stiff-mud machine process, cut by automatic cutter. The com- 
pany has been in operation for two years. 
The Union Stone and Brick Company is operating at Vance station, 
on the Baltimore and Ohio Railroad. The pit from which the shale 
is obtained contains 15 to 20 feet of shale, above 40 feet of a micaceous 
sandy bed. For brick-making two parts of the lower bed and one 
part of the upper bed are used. The output in 1903 is reported to 
have been 1,500,000 brick. 
WATER RESOURCES. 
SURFACE DRAINAGE. 
The Amity quadrangle contains no streams of large size. The 
most important are Tenmile Creek and its branches, Chartiers, Little 
Chartiers, Mingo, and Peters creeks, all of which rise within the limits 
of the quadrangle or near its borders. The largest stream is Tenmile 
Creek, which flows eastward nearly across the southern part of the 
quadrangle and has as branches on its north side Bane Creek, Little 
Tenmile Creek, and Daniels and Little Daniels runs. Chartiers Creek 
rises southwest of Washington, but flows for several miles in the quad- 
rangle. All the streams are tributary to Monongahela River, which 
is only a few miles distant everywhere east of the quadrangle and 
nearly touches its southeast corner. The entire quadrangle is covered 
with a fine network of runs, tributary to the larger streams. 
