194 ANNUAL REPORT 
One week; one day in air, six days in water, 30 to 50 pounds. 
One month (28 days); one day in air, 27 days in water, 50 to 80 
pounds. 
One year; one day in air, the remainder in water, 200 to 300 pounds. 
The specific gravity of Roman cements varies so greatly that it cannot 
be considered a criterion of its value. 
NATURAL CEMENTS IN OHIO. 
This industry is very insignificant in this State, being represented at 
present only by one plant in operation, two others being idle. ‘The plant 
in operation is located at New Lisbon, while the other mills are at De- 
fiance and Bellaire. The mill at New Lisbon is a small plant, having five 
kilns, of which, however, only two or three are operated at present, having 
a capacity of from 100 to 150 barrels a day. [he mechanical outfit is 
very simple, consisting of a cracker and buhr mills, one 3 foot buhr mill 
turning out about 100 barrels a day. A 50 horsepower engine operates the 
mill. The stone is mined, eight miners and one driver being employed. 
For each car of 3,500 pounds, 16 shovels of good bituminous coal is 
added when charging the stone into the kiln. The kilns are about 30 
feet high and have an inside diameter of about 10 feet. Three of the 
kilns are built together in a block, while two of them are iron jacketed and 
separated. Once a day, in the morning, each kiln in operation is drawn, 
furnishing about 50 barrels. When operating two kilns, 14 men are em- 
ployed altogether, eight miners and one driver, two kiln men and three 
mill men. When running two more kilns, three more men are needed. 
The mill at Defiance works the dolomitic rock, whose outcrop forms 
the bed of the Auglaize River, and is a material high in bituminous mat- 
ter and pyrites. The latter are especially obnoxious, and form regular 
bands, which are rejected as much as possible. On burning, the iron sul- 
phide causes the cement to clinker and stick, forming a sponge-like por- 
ous mass which is thrown away. The two kilns are cylindrical, 18 feet 
high, and 6 feet inside diameter, widening out at the bottom so as to mini- 
mize sticking as much as possible. Each kiln is fired from two furnaces, 
a cheap grade of wood having been the fuel used. From each furnace 
two openings lead into the kiln space. Owing to the fact that the stone 
is high in bituminous matter, the fuel necessary is small in amount, from 
one-quarter to one-half cord of wood per day. The chief difficulty is in 
holding back the burning so as to prevent clinkering and to oxidize the 
iron pyrites. Sometimes the clinkered cement chokes up the holes lead- 
ing from the furnaces into the kiln. The stone is drawn at short inter- 
vals, every thirty minutes, from five to eight, or even twelve wheelbarrows 
being obtained. At the same time a corresponding amount of stone is 
charged on top. The machinery consists of a crusher and a buhr mill, 
three feet in diameter, which must be dressed every three days. The or- 
