MBING TEST.

A recent trial of a smoke rocket for testing drains, described by Mr.
Cosmo Jones in the _Journal of the Society of Arts_, is deserving of
interest. The one fixed upon is 10 in. long, 21/2 in. in diameter, and with
the composition "charged rather hard," so as to burn for ten minutes. This
gives the engineer time to light the fuse, insert the rocket in the drain,
insert a plug behind it, and walk through the house to see if the smoke
escapes into it at any point, finishing on the roof, where he finds the
smoke issuing in volumes from the ventilating pipes. The house
experimented upon had three ventilating pipes, and the smoke issued in
dense masses from each of them, but did not escape anywhere into the
house, showing that the pipes were sound. If the engineer wishes to
increase the severity of the test, he throws a wet cloth over the top of
the ventilating pipe, and so gets a slight pressure of smoke inside it.

* * * * *

THE GAS ENGINE.[1]

[Footnote 1: Lecture by Mr. Dugald Clerk, before the Literary and
Philosophical Society, Oldham.]

By DUGALD CLERK.

In earlier days of mechanics, before the work of the great Scottish
engineer, James Watt, the crude steam engines of the time were known as
"fire engines," not in the sense in which we now apply the term to
machines for the extinguishing of fires, but as indicating the source from
which the power was derived, motive power engines deriving their vitality
and strength from fire. The modern name--steam engine--to some extent is a
misleading one, distracting the mind from the source of power to the
medium which conveys the power. Similarly the name "Gas Engine" masks the
fact of the motors so called being really fire or heat engines.

The gas engine is more emphatically a "fire engine" than ever the steam
engine has been. In it the fire is not tamed or diluted by indirect
contact with water, but it is used direct; the fire, instead of being kept
to the boiler room, is introduced direct into the motor cylinder of the
engine. This at first sight looks very absurd and impracticable;
difficulties at once become apparent of so overwhelming a nature that the
problem seems almost an impossible one; yet this is what has been
successfully accomplished in the gas engine. Engineers accustomed to the
construction of steam engines would not many years ago have considered any
one proposing such a thing as having taken leave