PREFACE. 



This volume has been prepared and will be published under the 

 provisions of an act of the Thirty-second General Assembly, author- 

 izing the publication of Volume 7 of the Geological Survey of Illinois, 

 approved May 26, 1881. 



The first section of the volume is devoted to economical geology, 

 and mainly to a record of the development of the coal resources of 

 the State since the publication of the last preceding volume in 1875. 

 The mining interests of the State are now second only in import- 

 ance to those of agriculture, and although the information obtainable 

 in regard to many of the experiments made with the drill, as well 

 as that to be derived from the shafts but recently sunk within the 

 borders of our coal-producing area, has in many cases been incom- 

 plete and unsatisfactory, through the non-preservation of the records 

 kept by those having the work in charge, yet the data obtained, 

 although by no means as complete as could be desired, will, I 

 trust, prove of considerable value, and tend to the further develop- 

 ment of this important industry. 



Sections two and three are devoted to the description and illus- 

 tration of the fossil forms belonging to the Carboniferous formation 

 of the Mississippi valley, and, as these are mostly new to science, 

 their publication will constitute an additional, and, I trust, an 

 acceptable contribution to our present knowledge of the specific 

 character of the Carboniferous fauna of the North American conti- 

 nent. 



In our work on the vertebrates, I have had the assistance of Mr. 

 Orestes St. John, of Topeka, Kansas, whose familiar acquaintance 

 with the fossil fishes of the palaeozoic rocks render his work of 

 special value to those interested in this department of palaeontology. 



