E. B. Andrews— Comparison of the Alleghany Coal-field. 289 
came over the great marginal plateau already described, we 
may well infer that there could not have been an extension 
through the anthracite region of the geosynclinal valley. 
There was only enough of greater depth to include the in- 
creased thickness of the conglomerate. 
e comparison of the two sides of the Alleghany coal- 
field suggests a very great difficulty in regard to the determina- 
tion of the place of what is termed thé coal-measure Conglom- 
erate. Is there an established horizon for such Conglomerate 
in American geology? In Ohio we now are in the habit of 
calling that rock the Conglomerate which, when found at all, 
hes upon the Waverly (although formerly the Waverly con- 
glomerate was also thus designated) and is approximately from 
600 to 800 feet below the horizon of the Pittsburgh seam of 
coal. The same Conglomerate extends under the bituminous 
coal-field of Western Pennsylvania and holds the same rela- 
tion to the Pittsburgh coal. This conglomerate horizon should 
have the same relative distance below the Pittsburgh seam in 
West Virginia, and I think I have probably found lithological 
proof of it in a very coarse conglomerate on Elk River—a 
branch of the Kanawha which enters the latter at Charleston. 
t the Kanawha Falls is a conglomerate more than 1000 feet 
lower in the series. This rock has been honored with a capital 
C, and the coals in the 1200 feet below it are spoken of as the 
Conglomerate series. Still below this series and below all the 
coals, Prof. W. B. Rogers finds another conglomerate in the 
New River valley as does Prof. Lesley under the lowest coals 
im the faults and upthrows to the southwest. Now if the coal- 
measure Conglomerate is a geological horizon and not merely 
a rock, these various strata cannot all be the true Conglom- 
erate. We find conglomerates everywhere in the vertical range 
of the coal-measures. They are found even above the horizon 
of the Pittsburgh seam. Heavy conglomerates abound along 
the western side of the eastern Kentucky coal-field, at various 
elevations above the lower Carboniferous limestone, and the 
Same is true in Tennessee. 
In the Indiana and Illinois coal-field, the coal seams of which 
have never been synchronized with those of the Alleghany 
coal-field, we have reported a conglomerate or millstone grit, 
but no one knows its exact place in the great time scale, or 
whether it is the equivalent of any of the half dozen well- 
marked conglomerates of the Alleghany field. So far as we 
how know it may have no equivalency any where. : 
In Arkansas there is a conglomerate called in the Geological 
Reports the Millstone gtit. The available coals of the State 
are said to lie below it, and are therefore called the Sub-Con- 
glomerate coals, although Prof. Lesquereux asserts that they 
Am. Jour, 8cr.—Tump — Vor. X, No. 58 —Ocr., 1875. 
