606 GEOLOGY OF OHIO. 



The bone bed is the boundary between two very distinct divisions of 

 this series of limestone — viz., the Delhi and Delaware beds of Professor 

 Winchell. The latter division is locally known as the " blue limestone," 

 to distinguish it from the underlying courses. It differs from these 

 courses in color, in style of bedding, in chemical constitution and in fossil 

 contents. The color of the stone is uniformly blue. In bedding it is 

 very even and regular. It contains a notable proportion of silica and 

 alumina in its composition, which militates against its durability as a 

 building stone. It would otherwise answer an admirable purpose for this 

 use, the thickness of the layers, which average six inches, the regularity 

 and the color all recommending it above any other limestone of the vi- 

 cinity. Some beds are found that can resist the weather, and these come 

 to be valued highly. 



The fossils of the Delaware beds are at this point chiefly fish remains. 

 Teeth, plates, jaws, and other bones are not infrequently met with through- 

 out twenty-five feet of this series. The uppermost seven or eight feet 

 consist of very thin and shaly beds, which contain flint in large quantity. 

 They are, as a rule, without fossils of any sort. The Delaware beds of 

 this immediate section are thirty-two feet in thickness. Their upper 

 boundary is as distinct as their lower, consisting of the blue shales that 

 make the base of the great system of Devonian shales that succeed this, 

 the last of the Paleozoic limestones of Ohio. 



AH but one, the lowermost, of the elements of the Cofniferous limestone 

 of the county are shown in this interesting section. Before treating of 

 other sections in detail, it will be well to establish the divisions of the 

 formation which it is proposed to recognize here. Two well marked divi- 

 sions have already come to view in the section just described, viz., the blue 

 limestone, thirty-two feet in thickness, which is, from its occurrence at 

 Delaware, and the extensive use made of it at that point, well named the 

 Delaware limestone ; and secondly, the white and buff limestones which 

 occupy forty-five feet of the scale below the Delaware beds. Though the 

 several portions of this last named section difier from each other consid- 

 erably in color, bedding and composition, the difierences found are not 

 marked and constant enough to demand recognition, and the whole of 

 this section will be designated the Columbus limestone. This name was 

 first given to it by Dr. Newberry, in Vol. I, Geological Survey of Ohio, 

 page 143. It is in all respects a suitable name, marking a central and 

 well known locality where the formation is most largely displayed and 

 worked. The Columbus limestone will be held to include all of the beds 

 intervening between the waterlime group of Upper Silurian age, and 

 the bone bed to which reference has already been made. The Delaware 



