58.4 lb. of this coal, and 2,000 lb.
of coal is equal to 34,246 cubic feet of natural gas. Then, if this coal
cost 26s. per ton, 1,000 cubic feet of natural gas is worth 91/2d. for its
heating power. In collecting samples of this gas I have noticed some very
interesting deposits from the wells. Thus, in one well the pipe was
nearly filled up with a soft grayish-white material, which proved on
testing to be chloride of calcium. In another well, soon after the gas
vein had been struck, crystals of carbonate of ammonia were thrown out,
and upon testing the gas I found a considerable amount of that alkali,
and with this well no chloride of calcium was observed until about two
months after the gas had been struck. In these calculations of the
heating power of gas and coal no account is of course taken of the loss
of heat by radiation, etc. My object has been to compare these two fuels
merely as regards their actual value in heat units."

Bearing in mind that it is never wise to prophesy unless you know, I
hesitate to speak of the future; but considering the experience we have
had in regard to the productiveness of the oil territory, which is now
yielding 70,000 barrels of petroleum per day, and which has continued to
increase year after year for twenty years, I see no reason to doubt the
opinion of experts that the territory which has already been proved to
yield gas will suffice for at least the present generation in and about
Pittsburg.

* * * * *

A GAS-ENGINE WATER-SUPPLY ALARM.

[Illustration]

A very useful contrivance for the purpose of reporting automatically the
failure of the water supply to a gas-engine has been arranged by
Professor Ph. Carl, of Munich. What led to the adoption of the device was
that, during last winter, the water supply in the neighborhood of the
Professor's laboratory was several times cut off without previous notice;
the result being the failure of the water needed for cooling the cylinder
of his Otto gas-engine. On inquiring into the matter, he discovered that
the same thing frequently occurred in other places where gas-engines were
in use; and this caused him to design a contrivance to put an alarm-bell
into action at the instant when the water ceased to flow, and so enable
any overheating of the engine, and injuries thereby resulting, to be
prevented in time. The arrangement (represented half size in the
accompanying engraving) is screwed down dir