Steward, which were most carefully made. Everything was measured--the
gas by a 60 light, and the air by a 300 light meter; the indicated
horse power, by a steam-engine indicator; the useful work, by a Prony
brake; the temperature of the water, by a standard thermometer; and
that of the escaping gases, by a pyrometer. The gas itself was
analyzed; and its heating power calculated, from its composition, as
617.5[theta]. Its specific gravity was .464; and the volume of air was
about seven times that of the gas used (or one-eighth of the mixture),
and was only 11½ per cent. by weight more than was needed for perfect
combustion. The results arrived at were as follows:

Per cent.
Converted into indicated horse power,
including friction, etc. 17.0
Escaped with the exhaust gas. 15.5
Escaped in radiation. 15.5
Communicated to water in the jacket. 52.0


It will thus be seen that more than half of the heat is communicated
to the water in the jacket. Now, this is the opposite of the
steam-engine, where the jacket is used to transmit heat _to_ the
cylinder, and not _from_ it. This cooling is rendered necessary,
because without it the oil would be carbonized, and lubrication of the
cylinder rendered impossible. Indeed, a similar difficulty has
occurred with all hot-air engines, and is, I think, the reason they
have not been more generally adopted. I felt this so strongly that,
for some time after the introduction of the gas-engine, I was very
cautious in recommending those who consulted me to adopt it. I was
afraid that the wear and tear would be excessive. I have, however, for