WESTERN COAL MEASURES AND INDIANA COAL. 557 
Two and a half miles east of Terre Haute, coal N, which is 
worked by a shaft at Seebyville, crops out; this indicates a rise of 
the strata to the west, and, as a still further means of accounting 
for the absence of the upper part of the coal measures in these 
bores, it is possible that the great bed of drift which is found on 
the east bank of the Wabash river, at Terre Haute, filled up a 
ravine or valley from which some of the upper coal beds were re- 
moved by abrading forces. 
On the west bank of the river, coal L is mined in a number of 
places from shafts, thirty to fifty feet deep. 
From the foregoing data, therefore, I am enabled to correct the 
error into which I fell in my First Report, 1869, of making the 
top coal in the Terre Haute bores, coal L., and now place it at 
least as far down as coal I. 
Though from the records that were kept of these bores, it is 
difficult to point out the base of the coal measures, or that of the 
Millstone grit, with any degree of accuracy, it is, nevertheless, 
my opinion, that the latter epoch commenced at about the depth 
of five hundred feet. 
This thinning out of the coal seams as we go west towards the 
centre of the basin, is a remarkable feature which I first pointed 
out in 1867. A few miles west of the Indiana line in Clark 
county, Illinois, bores have been made in searching for petroleum, 
to the depth of eight hundred feet, without passing a single work- 
able seam of coal, and the two or three thin seams reported, in 
some of these bores, are in the upper part of the measures. 
Judged by the dip of the coal on both sides of the river, the 
Wabash runs on a slight anticlinal axis, and I believe this to be 
the case from Attica, in Fountain county, to its mouth in Posey 
county, and that along its course it cuts through the same strata 
of rocks, from the bluffs at Merom to its confluence with the Ohio 
river. 
Near the eastern boundary of the zone of caking coals, in Indi- 
ana, we find K and L, and sometimes N, of good, workable thick- 
ness, averaging from four to eight feet, and in one locality at Pike 
county, there is a bed not yet studied, but thought to be K, that 
attains to the thickness of ten feet or more. Taken all together, 
the maximum thickness of these beds may be estimated at twenty 
feet, and will yield an average, over the greater part of the dis- 
trict, of ten feet of coal. At some localities the caking coal is of 
