the
internal-combustion engine continue to reign supreme, or will
increasing power demands of the huge planes to come lead to
the development of suitable steam-engines? Will the use of
petroleum continue to be one of the triumphs of aviation, or
will the time come when substitutes may be successfully
utilized?

For aerial motive-power, the principal requirements are:
great power for weight with a fairly high factor of safety,
compactness, reliability of operation under flying
conditions, and safety from fire. Bulk and weight of
steam-driven equipment apparently impose severe restrictions
upon its practical development for present aircraft purposes,
but who is willing to classify its future use as an
absurdity?

Steam operation in small model airplanes is no innovation.
Langley, in 1891-1895, built four model airplanes, one driven
by carbonic-acid gas and three by steam-engines. One of the
steam-driven models weighed thirty pounds, and on one
occasion flew a distance of about three thousand feet. In
1913 an Englishman constructed a power plant weighing about
two pounds which consisted of a flash boiler and
single-acting engine. This unit employed benzolin, impure
benzine, as fuel, and propelled a model plane weighing five
pounds.

_Power Plant Engineering_, Chicago, June 1, 1919

Making a Brief. The next step after making outlines or briefs of
material already organized is to make your own from material you
gather. Speeches you have already prepared or considered as fit for
presentation will supply you with ideas if you cannot work up new
material in a short time. At first you will be more concerned with the
form than the meaning of the entries, but even from the first you
should consider the facts or opinions for which each topic or
statement stands. Weigh its importance in the general scheme of
details. Consider carefully its suitability for the audience who may
be supposed to hear the finished speech. Discard the inappropriate.
Replace the weak. Improve the indefinite. Be sure your examples and
illustrations are apt.

Be wary about statistics. In listening to an address many people begin
to distrust as soon as figures are mentioned. Statistics will
illustrate and prove assertions, but they must be used judiciously. Do
not use too many statistics. Never be too detailed. In a speech,
$4,000,000 sounds more impr