670 GEOLOGY OF OHIO. 



thin-bedded, yellowish shaly limestone. The shale is much the more 

 constant and abundant of the two, the limestone layers coming in as a 

 rule near the bottom of the series, at the same horizon where the Dayton 

 stone is found when it occurs. In other words, the Dayton stone, in excep- 

 tional instances, replaces these shaly layers. The last named phase of 

 the formation is shown very distinctly in the section on the Grinnell ' 

 pike. The composition of the shale proper is shown by the following 

 analysis, made by Prof. Wormley : , 



Carbonate of lime 34.40 



Carbonate of magnesia 30.87 



• Silicate of lime 8.48 



Alumina and iron 8.40 



Silica 12.21 



Water, combined 5.40 



99.78 



There are occasionally found in the shale numerous crystals and nod- 

 ules of sulphuret of iron. In some of the sections shown in the Glen at 

 Yellow Springs such nodules abound. They are often construed by the 

 ignorant as indicating mineral treasures in the rocks which are here 

 shown. A pit near the mouth of the Cascade Branch, six feet in diam- 

 eter, and certainly more than twenty feet in depth, walled with timber, 

 and now partly filled with rubbish, the origin of which is unknown to 

 the oldest inhabitants, seems to show that such deceitful expectations 

 were awakened in the minds of the earlier occupants of the country. 

 Such unsuccessful experiments serve to show that our predecessors knew 

 less than we now know of the contents of the strata, rather than more, 

 as the credulous sometimes believe. The excavation was carried down 

 into the Clinton limestone, the whole thickness of which might have 

 been seen and studied by passing down the valley for half a mile. 



The surface of the Niagara shale is a very important water-bearer for 

 this whole region, giving rise to a line of strong springs along its out- 

 crops, and supplying the largest number of the drilled wells of the table- 

 land. More extended mention will be made of this subject in a subse- 

 quent part of this report. 



(c.) The next element in ascending order is the formation termed 

 in the report on Highland county the West Union Cliff. This stratum 

 would certainly not be erected into a separate division from any facts in 

 its occurrence in this part of the State ; but in Adams-county it attains 

 a thickness of ninety feet, and constitutes, in several of the southern 

 counties, a very marked and important element in the Niagara series. 

 In Greene county, as in Clarke, it does not exceed eight feet -in thick- 



