PREFACE. IX 
On six of the sheet maps that accompany the volume, viz., Nos. 4, 5, 6, 7,8 and 9, 
there are laid down the areas actually occupied by the most important geological 
element or elements of the district represented. As to what the most important 
elements are, there can scarcely be any difference of opinion. The Kittanning coals 
in the northern counties and the Ferriferous limestone in the sovthern are uni- 
versally recognized as far in advance of all other horizons in economic interest. 
Though known by different names, they constitute practically one continuous series, 
so that we now have an inner line of outcrop within the Coal Measures from the 
Ohio Valley as far northward as Stark county. From this point, eastward to the 
Pennsylvania line, the face of the country is so heavily overlain with drift that it is 
impossible to follow the formations in detail. 
This division of the Coal Measures into distinct areas will be recognizei by all 
students of our geology asa step in advance. Itis, however, but one step where 
several need to be taken. The Mercer and the Freeport areas deserve to be added 
to those already represented. 
Extreme accuracy is not claimed for these maps, but the general distribution of 
the coal and ore areas is adequately shown upon them, and they also indicate where 
mines and railroad extensions can be properly located. The revelations that they 
make asto the areas of our coals will, in some cases, prove surprising even to those 
best acquainted with the districts represented. In almost every case, the measured 
areas prove smaller than previous estimates had made them. 
The acknowledgments which I owe for assistance of various sorts in the prepara- 
tion of this volume are so numerous that I cannot undertake to make individual 
mention of them all. In every section of the State in which I have worked, I have 
received invaluable assistance from well-informed and public-spirited citizens. The 
information derived from such sources has been blended with knowledge otherwise 
obtained, but it constitutes no small part of the account of our mineral wealth which 
I have here undertaken to present. : 
There are, however, certain persons whose services, in connection with the 
volume, have been such that it would not be right to pass them by without par- 
ticular mention. 
First of all are to be named the Trustees of the State University, who, by their 
liberal policy, have rendered it possible for me to undertake and carry forward the 
work herewith presented, in connection with my college duties. During the last 
two years they have, from time to time, granted me such exemption from these 
duties as I have required in order to collect and arrange the materials of this 
volume. I desire to place upon record my high appreciation of their considerate 
action. 
To Hon. T. C. Snyder, of Stark county, a member of the 65th General As- 
sembly, is due the credit of introducing and urging the legislation by which the 
completion of this volume was provided for. To the same gentleman, aided by 
Hon. James Scott, of Warren county, is also due the introduction of the bill by 
which the present publication was secured. 
To the following-named gentlemen I am indebted for special assistance in 
working out the several districts in which they reside or in the correction and 
criticism of the statements published in regard to these districts. While they have 
helped me to the facts which I have used, it does not follow that they will in all 
