PREFACE. 



The volume which follows is the third and last of those which constitute the purely geolo- 

 gical portion of the report required of the Geological Corps by the organic law of the 

 Survey. Material sufScient to form a volume equal in size to the two before published 

 was prepared, and its publication was authorized more than three years since, but its ap- 

 pearance has been delayed by various causes, chief among which was the rapid develop- 

 ment of the coal and iron Industries in the southeastern portion of the State, and the 

 important discoveries made during the progress of the extensive explorations under- 

 taken in this region. The credit of the Survey, and the interests of all those who were 

 taking part in the development of the resources of this section, seemed to require that a 

 new and thorough survey of at least the Hooking Valley Coal Field should be undertaken. 

 This has been done with much care, and with very gratifying and satisfactory results, 

 and the pages which follow give ample evidence of the importance and even necessity 

 of this re-survey. 



Much work has also been done daring the interval in other parts of the State, correct- 

 ing errors that have been made, or adding to the facts before gathered. In this way 

 the dimensions of the volume now published have been considerably augmented, and its 

 value greatly enhanced. It should also be said that the new material added to the 

 volume has been acquired at very small cost to the State, as since 1874 no regular 

 salaries have been paid to the members of the Geological Corps, and the small sum 

 appropriated since the above date has been no more than sufficient to pay the actual 

 expenses incurred in field and office work. Hence the delay has been a gain rather 

 than a loss to the people of Ohio. 



Part H of this volume, constituting the third and last contribution to the Palceontology 

 of the State, is in the course of preparation, and will be ready for presentation to the 

 next Legislature. 



5" Vol. IV, Zoology and Botany, is now in the printer's hands. The Geological Map of 

 the State will be ready for distribution this year. Vol. V, Economic Geology, is more 

 than half done, and it is expected that the material necessary to complete it will be 

 added during the coming year. It will be impossible for the public to justly estimate 



