xii PREFACE. 
Of the Third District—Butler, Clinton, Darke, Fayette, inhevelsetta Miami, Preble, 
Warren. 
Of the Fourth District—Champaign, Logan, Shelby. 
| It will be seen that the above list includes some of the richest and most populous 
agricultural and mining counties in the State, and it would be a great injustice to their 
inhabitants if, after paying their portion of the general expenses of the Survey and 
for the publication of reports on other portions of the State, they were denied their 
share of the benefits of the Survey. The matter for the third volume has been, to a 
considerable extent, prepared since the apprepriations for the salaries of the Geological — 
Corps were discontinued; much of it is, therefore, a gratuitous contribution, with 
which the Corps should be credited when a comparison is made between the value of 
their services and the compensation they have received. Some of the neyo and other 
illustrations of this volume are already engraved, so that the cost of its publication 
will be something less than that of either of its predecessors; in other words, from 
seventy-five cents to one dollar a copy, according to the size of the edition published. 
A large amount of new paleontological material has been gathered dues the last 
_ year, which, with that crowded out of previous reports by the necessary limitation of 
space and expense, would, if fully described, go far toward forming & third volume 
on Paleontology; but no such volume has been had in contemplation, and it may 
very well remain as a subject for farther leetiaikenfiom, when the financial condition of 
the country shall better justify the expenditure of the money necessary for its pub- 
lication. 
As the value of the palzeontological portion of our report is still underestimated in 
some quarters, it may moti be out of place to repeat here what has been said on this 
subject in some of our former reports, viz., that the fossils found in our rocks are not 
mere objects for idle curiosity, but are of the highest practical importance, since 
they, in fact, constitute the only reliable guides in the study of our sediméntary 
rocks. The whole system of classification in modern geology is based upon them, and 
it is not too much to say that no man can be a good geologist who has not consider- 
able familiarity with them. Figures and descriptions of the characteristic fossils of 
our formations will, therefore, prove of great utility to our students and teachers of 
geology; and it is, indeed, difficult to see how they can make much progress in the 
study of the geology of the districts in which they live without the assistance they 
afford. It is also true that the wealth and power of any community consist quite as 
much in the ideas in their heads as the dollars in their pockets; and it is even prob- 
able that the revelations which have been made through the Geological Survey, of 
the strange and varied extinct forms of life with which our rocks are crowded, will 
