Cement, when taken from the furnace, weighed 110 lb. per bushel.
Cement, when ground, leaving 10 percent. on sieve with 2,500 holes to
the inch, weighed 121 lb. per bushel, and when cold 118 lb. per
bushel. When made into briquettes, the tensile breaking strain upon
the square inch:

At 4 days was 410 lb. per square inch.
At 6 days " 610 " " " "
At 14 days " 810 " " " "
At 49 days " 900 " " " "
At 76 days " 1,040 " " " "

A cylindrical furnace, such as the author has described, is capable of
turning out at least 20 tons of good cement per day of twenty-four
hours, with a consumption of about 3 tons of slack coal. It will be
readily understood that these furnaces can be worked more economically
in pairs than singly, as they can be so arranged that one producer may
furnish a sufficient quantity of gas for the supply of two cylinders,
and the same labor will suffice; but in order to provide for possible
contingencies the author advises that a spare gas producer and an
extra furnace should be in readiness, so that by a simple arrangement
of valves, etc., two cylinders may always be in operation, while from
any cause one may be undergoing temporary repairs, and by this means
any diminution in the output may be avoided.

The author considers it unnecessary here to discuss either the
advantages or the economy of fuel effected by the employment of gas
producers for such a purpose. These have been abundantly proved in
steel and glass making industries, where a saving of from 50 to 70 per
cent. of the fuel formerly employed has been made. Their cost is