AUTHOR'S PREFACE. 



This book contains a short historical and industrial sketch, 

 a chapter on Physiography, seven chapters on Geology, three 

 chapters on Mineral Resources, and a chapter on Paleontology. 



In order to describe the several coals and the oil and gas 

 sands in their proper stratigraphic sequence, it was necessary to 

 make an exhaustive study of the entire rock system, both sur- 

 face and underground as far as possible, and to embody a large 

 part of this research in the text in the form of geologic sections 

 and detailed descriptions. This matter may not be of interest 

 to the casual reader but its value to professional men conducting 

 future coal, oil and gas operations in the two counties can not 

 be questioned. 



Two maps accompany the Report in a separate atlas. Map I 

 consists of the topographic sheets of the U. S. Geological Sur- 

 vey assembled in convenient form to make a complete surface 

 map of the two counties. Map II, showing General and Eco- 

 nomic Geology, gives not only the structure contours based on 

 the bottom of the Pittsburgh Coal, but also the accurate location 

 of, all the oil and gas wells and coal test borings, of which 807 

 are listed by number both on the map and in the text, and the 

 accurate location by number of the 284 coal openings examined 

 and described. Besides these separate maps, 12 figures appear 

 in the text, of which Nos. 4 to n, inclusive, are intended to show 

 at a glance where the several coal seams are of minable thick- 

 ness and purity. Since these coals are too thin or impure 10 be 

 minable in certain regions, it has been necessary in most of the 

 figures to make Approximate Lines of Disappearance, in referring 

 to which it must be remembered that there -are probably a few 

 patches of good coal on the barren side and corresponding areas 

 where the coal is worthless on the side where coal is shown. 

 Wherever possible, detailed information should be secured from 

 openings or borings published in the text. 



The author spent the field season of 1914 making the neces- 

 sary researches for this volume, and is responsible for all the 

 data contained in Parts I, II and III, but was helpful in the office 



