40 W.S. GRESLEY—CLAY-VEINS INTERSECTING COAL MEASURES. 
which disappear in the strata under the Pittsburg coal bed, as well as 
pass out of sight in the strata immediately above that bed. Doubtless 
many other examples of these phenomena could be obtained, but aip- 
parently some clay-veins do not descend below the coal bed, or possibly, 
where invisible, they have suffered annihilation locally from enormous 
side pressure. Nor doesit appear that they always run entirely through 
the coal, for some do not reach beyond the lower benches of the seam, 
while others seem to stop short at the base of the upper layers—that is, 
2B 
KR \ y) 
Direction of Cleat == 
Z al, = 
Dip of the coal. % 
Thickness of coal, 519” 
“Depth to the coal, 200! 
1 
Thickness of coal, 6 
Direction of Cleat. SS 
Scale: in the coal. Scale: 
o 100 200 Ft. Dip of the seam. * 0 100 2pore. 
Figure 6.—Plan of Clay-veins in the Pacific Mine. Figure 7.—Plan of Part of most prominent Clay- 
4 , veins in the Florence Mine. 
As surveyed in an area of about 31 acres of 
mine workings in the ‘‘ Pittsburg” coal seam, As proved by mining at depths between 150 
Allegheny county, Pennsylvania. and 300 feet in the Pittsburg coal bed, near Ray- 
mond, Putnam county, West Virginia. 
about the middle of theseam. The veins often divide and reunite within 
the height of the coal bed. The crooked forms of the veins, together 
with the faulting of their walls, have produced nips or pinches, which 
cause the veins to appear to end where they do not. 
PROXIMITY TO ONE ANOTHER 
In the “ Pittsburg ” seam near Sewickley, in Westmoreland county, 
Pennsylvania, the writer counted five substantial clay-veins within a hori- 
