502 PAL.EONTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 



ber of specimens, which have been subjected to your examination. 

 From them it is evident that the distribution of the species of shells 

 in the shales of a bed of coal is as reliable, for its identification, as 

 the distribution of the species of fossil plants. 



The following introductory remarks may appear out of place in a 

 local report like this, but I think that they are not without a practical, 

 advantage. They will give not only an answer to a question scarcely 

 understood as yet, and often put to us by persons interested in the 

 coal business, viz : what is the coal, and how has this fuel been formed ? 

 But they will also enable the reader fully to understand the practical 

 deductions, and to test their value. 



It is unnecessary to dwell on the advantages of undoubtedly ascer- 

 taining the geological level of a bed of coal, since it is evident that 

 profitable explorations for coal can be made, with some chances of 

 success, only from the directions of a previously ascertained and well 

 established geological level. When this is exactly ascertained, a sin- 

 gle glance at a vertical section of the measures gives an answer to the 

 question: at what distance above or below shall we expect to find 

 another coal, and what will possibly be the thickness of the bed? 



The few quotations and references to researches previously made by 

 myself, in the coal-fields of Pennsylvania and Ohio, will be easily 

 excused, since they tend to solve the problem of the coeval formation, 

 even of the primitive connection of all the coal-fields of the United 

 States — a question most . interesting for geology, and eagerly discuss- 

 ed just now. And as for the right I may have to quote a few lines of 

 a report delivered in 1&54, to the director of the Geological State Sur- 

 vey of Pennsylvania, and of which a small pamphlet, " Description of 

 netv species of fossil plants, $"c," has only been published, I do not 

 think that it can be denied me. This report, elaborated with great 

 care, and the arduous labor of two years, was to appear in the final 

 report of the Geological State Survey of Pennsylvania, but it is a 

 question if it will ever be published. Therefore, I do not think that 

 I*am bound to entirely disregard some scientific results, which may be 

 of general advantage, for the only reason that they have been made 

 under the direction of another state. 



I am, sir, most respectfully, yours, 



LEO LBSQUBEEUX. 

 Dr. D. D. Owen , Director of the BUM Survey of Kentucky* 



