516 GEOLOGY OF OHIO. 
however, that by going down twenty or twenty-five feet at Bierley’s 
quarries, a portion of rock will be found 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 Hmestone or typical 
dolomite. The analysis, as given by Dr. Wormley, Chemist of the Sur- 
vey, gives to it the remarkable per cent. of carbonate of magnesia, 50.11, 
a per cent. exceeding that of carbonate of lime. Prof. Orton, however, 
would make some allowance #for this high percentage as being the result 
of a long-continued presence of carbonated water. But, even at Gard’s 
quarries, the rock shows a percentage of 45.72 carbonate of magnesia. 
The analysis, in detail, of three specimens, frona different quarries in the 
the county, shows : | 
Bierley’s Gard’s Northop’s 
euarries. quarries. | quarries. 
Carbonate of lime .-.--.------ A area 44.60 | 52.30 51.70 
Carbonate of magnesia ..2....------.--.--.--. | 90.11 40.72 45.26 
SWhien, teem, ayroxdl ellie ono osesod secoecs cessor 4.60 2.20 2.70 
SFO v2 1. (o pean ONE LA la Sac le LR NL SD Ua 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 sinsilar table, as to composition, in Vol. . 
II, page 676. 
ECONOMIC GHOLOGY. 
A rich and productive soil will always constitute the material wealth 
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 up in the innumerable kames. This 
atter too, 1 may urge, fomms no mean element. Its influence may be 
