516 



GEOLOGY OF OHIO. 



however, that by going down twenty or twenty-five feet at Bierley^s 

 quarries, a portion of rock will be Ibund sufficiently hard and well lam- 

 inated to subserve all the purposes of the ordinary " Covington stone." 

 Whether it would be feasible to- work it at such a depth, I am unable to 

 say. Such, building material as the Covington stone would be of inesti- 

 mable value to the county if it could be found at any point above drain- 

 age. 



The greatest economical value attaches to' this division of the Niagara 

 formation for the very fine quality of lime which it produces. The lime, 

 as obtained from these rocks in Darke county, I may say, has no superior 

 within the State. Its extreme whiteness and strength gives it an easy 

 market. 



Chemically considered, this rock is a magnesian limestone or typical 

 dolomite. The analysis, as given by Dr. Wormley, Chemist of the Sur- 

 vey, gives to it the remairkable per cent, of carbonate of magnesia, 50.11^ 

 a per cent, exceeding that of carbonate of lime. Prof. Orton, however^ 

 would make some allowance jfor this high percentage as being the result 

 of a long-continued presence of carbonated water. But, even at Gard'& 

 quarries, the rock shows a percentage of 45.72 carbonate of magnesia. 

 The analysis, in detail, of three specimens, from different quarries in the 

 the county, shows : 



Bierley's 

 quames. 



Card's 

 q,uarries. 



Northop'^B. 

 quarries. 



Carbonate of lime 



Carbonate of magnesia 

 Silica, iron, and alumna 



Totals 



44.60' 



50.11 



4.60 



51.3* 



45.72 



2.20 



51.70- 

 45.26 



2,70 



99.31 



99.22 



99.66 



The specific gravity of specimen No. 1, as determined by Prof. Menden- 

 hall, is 2.452. A table of comparisons as to specific gravities may be- 

 found in Vol. II, page 679, and a similar table, as to composition, in- Vol. 

 II, page 675. 



ECONOMIC GEOLOGT. 



A rich and productive soil will always constitute the material wealths 

 of Darke county. Add to this great source of wealth the extensive for- 

 ests which are spread all over the county, and the inexhaustible sup- 

 plies of sand and gravel stored ia,p in the innumerable kames. This 

 atter too, I may urge, forms no mean element. Its influence may be 



