weight, power, and mechanical force. Whenever Mr. Maxim can make
an engine strong and light enough, and sails large, strong, and
light enough, and devise the machinery required to connect the
sails and engine, he will fly. Science has nothing but encouraging
words for his project, so far as general principles are concerned.
Such being the case, I am not going to maintain that we can never
make it rain.

But I do maintain two propositions. If we are ever going to make
it rain, or produce any other result hitherto unattainable, we
must employ adequate means. And if any proposed means or agency is
already familiar to science, we may be able to decide beforehand
whether it is adequate. Let us grant that out of a thousand
seemingly visionary projects one is really sound. Must we try the
entire thousand to find the one? By no means. The chances are that
nine hundred of them will involve no agency that is not already
fully understood, and may, therefore, be set aside without even
being tried. To this class belongs the project of producing rain
by sound. As I write, the daily journals are announcing the
brilliant success of experiments in this direction; yet I
unhesitatingly maintain that sound cannot make rain, and propose
to adduce all necessary proof of my thesis. The nature of sound is
fully understood, and so are the conditions under which the
aqueous vapor in the atmosphere may be condensed. Let us see how
the case stands.

A room of average size, at ordinary temperature and under usual
conditions, contains about a quart of water in the form of
invisible vapor. The whole atmosphere is impregnated with vapor in
about the same proportion. We must, however, distinguish between