THE CARBONIFEROUS SYSTEM. 167 
and Tennessee, lead me to believe that great, and perhaps radical, differ- 
ences will be found to exist between the northern and southern portions 
of the Alleghany coal field. | 
Prof Andrews has shown that important modifications have taken 
place in our northern system, even within the limits of our own State. 
In West Virginia, Kentucky, and Tennessee these changes seem to be 
still more strongly marked, for there a lower series of coals appears to 
come in within and even beneath the Conglomerate; and it is very 
doubtful whether our leading seams can be identified there at all. The 
geological survey which has been recently revived in Kentucky, and com- 
mitted to the able supervision of Prof. N. 8. Shaler, will undoubtedly throw 
much light upon this question. When he shall have filled the great geo- 
logical blank which has heretofore existed in eastern Kentucky, and the 
mysteries of the rich and intricate coal fields of West Virginia shall be un- 
raveled, the work done in Pennsylvania and Ohio can be connected with 
that of Prof. Safford in Tennessee, and the broad and interesting problems 
of the structure and history of the Alleghany coal field will approach 
solution. Till then our generalizations on this subject must be largely 
speculative, and such as are liable to be greatly modified by future obser- 
vation. : 
In regard to the community of structure between the Alleghany and 
Illinois coal fields, I am compelled to say, that after some time spent in 
the examination of the coal strata of Indiana, Illinois, and western Ken- 
tucky, and a careful reading of the excellent reports of Professors Cox 
and Worthen, I have failed to find any proof of the identity that has 
been claimed. I have not been able to satisfactorily co-ordinate the 
series of coal beds of the two basins, nor can I identify any individual 
seam of the Illinois coal field by its position, its dimensions, its quality, 
its fossils, or its associated strata, with any one of ours. 
Mr. Lesquereux also claims to be able to identify the Mahoning sand- 
stone in the Coal Measures of Illinois and Kentucky. But in tracing it 
even through our portion of the Alleghany coal field I find it so often 
absent that it becomes entirely unreliable as a geological guide. That it 
has been so to Mr. Lesquereux is evident from the fact that he has sup- 
posed that he recognized the Mahoning in the heavy sandstone which 
overlies the Pomeroy coal, and in that which contains the silicified 
trunks of Psaronius on Shade river. As a consequence, he has regarded 
the Pomeroy coal as the Upper Freeport seam,* whereas it is well estab- 
lished that it is No. 8, or the Pittsburgh coal. 
*American Journal of Science, 2d Series, Vol. XX X., p. 368. 
