PREFACE. 



It becomes tny duty to set forth in this preface a brief account of the present 

 volume, to explain its composite character, in which it differs in some respects from 

 all its predecessors, and, as it is the last official volume that I expect to prepare, to 

 briefly point out the lines, along which the work of the Geological Survey has ad- 

 vanced, and the results that have been thus far attained. By the numbering under 

 which it appears the present volume is counted in with the reports that have pre- 

 c eded it during the last 21 years ; but as a matter of fact, it is the outcome of a dis- 

 tinct organization of the geological work of the State. 



The Second Geological Survey was organized in 1869 and was under the direc- 

 tion of the late Professor J. S. Newberry up to 1883, although his active work upon 

 it was substantially terminated in 1876. Under Dr. Newberry's direction, Reports of 

 Progress for 1869, 1870 and 1871, and Volumes I, II, III and IV were issued; includ- 

 ing also Volumes I and II, Paleontology, togther with a geological map of the State, 

 on a scale of four miles to the inch. In direct continuance of this work, volumes 

 V and VI were issued, under my direction as State Geologist, in 1884 and 1888 re- 

 spectively. A preliminary report on Petroleum and Gas was also published in this 

 series in 1886. 



The Second Geological Survey nominally terminated in 1888, with the publica- 

 tion of Volume VI ; but in the subsequent year (1889) provision was made by the 

 Legislature for the continuation of geological work on a small and inexpensive scale, 

 the results to be made known by annual reports. The direction of this work was 

 placed in my hands, but provision was made for only a part of my time. A report 

 was issued in 1890, entitled "First Annual Report of the State Geological Survey, 

 Third Organization." Shortly before the time for publication of the second annual 

 report, I was disabled in health to such a degree that it no longer seemed advisable 

 for me to continue the double duty which I was carrying on; and permission was 

 accordingly obtained from the 70th General Assembly to publish the material gath- 

 ered for the Second Annual Report together with certain other chapters, presently 

 to be named, under the title of Geology of Ohio, Volume VII. 



It was the original plan of my predecessor, Dr. Newberry, to divide each vol- 

 ume of his reports into two parts, the first covering general geology and the second; 

 paleontology. In pursuance of this plan, Volumes I and II were issued in two parts, 

 or, in reality, in two distinct volumes, the volumes in fact, differing in size and in 

 other respects. But when the time came for the publication of Volume III, the 

 finances of the State had become somewhat straitened, and the legislature to which 

 the volume was offered was disinclined to incur the large expense, viz., about ^60.000, 

 necessaryforpublishingthe paleontology on the scale on which the two preceding vol- 

 umes had been issued. The Legislature, however, authorized the publication of the 

 general geology part 1, under the title of Volume III. Considerable material had been 

 prepared under Dr. Newberry's supervision for the paleontological part of this volume. 

 A chapter prepared by Prof. R. P. Whitfield of the American Museum of Natural 

 History, New York, after having been held for several years without any indication 



