i6o Cincituiati Society of Natural History. 



MICROSCOPICAL STUDY OF OHIO LIMESTONES. 

 By G. Perry Grimsley, M. A., Columbus, Ohio. 



Although the general characteristics of the Ohio limestones 

 have been carefully investigated, both from an economical and 

 paleontological point of view, no extended stud}' has as yet 

 been made of their microscopical structure. That we may 

 have a complete knowledge of the history and structure of 

 limestones, this part of the study should by no means be 

 overlooked. 



The application of the microscope to the examination of 

 rocks in thin sections is a result of experiments of men now 

 living, and, as a result of their labors, a new branch of science 

 has come into existence known as Microscopical Petrography. 



For a couple of centuries men had been experimenting 

 along this line, but these were but the glimmering raj-s in the 

 darkness and perplexity of mineral study, heralding the com- 

 ing of a brighter light, which would reveal a new and vast 

 field for experiment and thought. 



The year 1850 may be said to mark tlie beginning of Modern 

 Petrography, when Mr. H. C. Sorby, of England, applied the 

 microscope to the examination of thin rock sections. But it 

 was in Germany that the greatest progress has been made, and 

 now the leader in the new science is the German investigator, 

 Rosenbusch, whose first great work appeared in 1S73. This 

 .soon attracted workers from all parts of the world. American 

 students brought the science across the water, and now we 

 have the names of Williams, Iddings, Cross, Wadsworth, 

 Adams and other workers connected with the science. Such 

 is a brief account of the introduction of the microscope into 

 geological work. 



The aim of the present paper is to note the structure, as 

 revealed by the microscope, of the great limestones of the 

 Ohio scale in Ihcir geological order, devoting especial atten- 



