No. 50.] 
403 
vals, there are courses of nearly pure sandstone ; sometimes a single 
layer of a few inches, at other times several, forming a mass of four to 
ten feet thick. 
A very good exliibition of this group, and better than is elsev^^here 
seen, in Allegany county, is on the Caneadea, from Rushford, near 
McCall's mills to the mouth of the creek. The rocks consist of nu- 
merous alternations of shale and sandstone, the latter often in layers of 
two or three inches, and other larger ones, v^hich are quarried for lock- 
stones, building stones, and grindstones. 
The following section commences near McCall's mills and termi- 
nates near the level of the Genesee river. The numbering is from the 
lowest to the highest rock : 
Feet. 
1 7. Hard siliceous sandstone, in thin courses, often having lines 
of irregular deposition and slightly conglomerated, 20 
16. Bluish green shale, with thin layers of Fucoidal sandstone, 15 
15. Green micaceous shale, 15 
14. Thin layers of sandstone separated by shale, 2 
13. Shale like No. 15, 15 
12. Shale, with six thin layers of sandstone, the lower layer of 
eight inches, being irregularly deposited, 14 
1 1 . Green sandy micaceous shale, 9-J- 
10. Sandstone, the surface corrugated as if water had evaporated 
from it while yet soft. (A few rods east of this point the 
layer thins to 4 inches,) 3 
9. Greenish shale like No. 11, _ 10 
8. Sandstone quarry, grindstone grit. (Farther west this mass 
consists of two layers of sandstone, each one foot thick, 
with four feet of shale.) 8 
7. Greenish shale, 12 to 15 
6. Concretionary sandstone, the upper portions sometimes re- 
gularly stratified, (variable in thickness,) 8 
5. Greenish and somewhat micaceous shale. The upper 20 
feet is traversed by irregular, vertical and inclined seams, 
distinct from joints, which cause it to split in those direc- 
tions, presenting a surface as if chopped with an axe. A 
striated fucoid is common to this part of the mass. The 
Carried foiAvard, 313 
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