Such a work as well as all other reports of the State Survey, 

 including also all maps and diagrams, should be placed on the 

 market at actual cost by the State, and would, I am sure, meet 

 with ready sale to students and others interested in the sub- 

 jects treated in these publications. 



I cannot close these remarks without expressing my obliga- 

 tion to Professor CHARLES W. ROLFE, of the Geological De- 

 partment of the Illinois State University, at Champaign, for his 

 valuable suggestions and frequent manifestation of interest in 



my work. 



I have the honor to be, 



Sir, 



Your obedient servant, 



JOSUA LIXDAHL. 



ILLINOIS STATE MUSEUM OF NATURAL HISTORY, 

 SPRINGFIELD, ILL, July 10, 1890. 



