at it was not the
sound of the cannon that produced the rain. That sound as a physical
factor is quite insignificant would be evident were it not for our
fallacious way of measuring it. The human ear is an instrument of
wonderful delicacy, and when its tympanum is agitated by a sound we
call it a "concussion" when, in fact, all that takes place is a sudden
motion back and forth of a tenth, a hundredth, or a thousandth of an
inch, accompanied by a slight momentary condensation. After these
motions are completed the air is exactly in the same condition as it
was before; it is neither hotter nor colder; no current has been
produced, no moisture added.

If the reader is not satisfied with this explanation, he can try a very
simple experiment which ought to be conclusive. If he will explode a
grain of dynamite, the concussion within a foot of the point of
explosion will be greater than that which can be produced by the most
powerful bomb at a distance of a quarter of a mile. In fact, if the
latter can condense vapor a quarter of a mile away, then anybody can
condense vapor in a room by slapping his hands. Let us, therefore, go
to work slapping our hands, and see how long we must continue before a
cloud begins to form.

What we have just said applies principally to the condensation of
invisible vapor. It may be asked whether, if clouds are already formed,
something may not be done to accelerate their condensation into
raindrops large enough to fall to the ground. This also may be the
subject of experiment. Let us stand in the steam escaping from a kettle
and slap our hands. We shall see whether the steam condenses into
drops. I am sure the experiment will be a failure; and no other
conclusion is possible than that the production of rain by sound or
explosions is out of the question.

It must, however, be added that the laws under which the impalpable
particles of water in clouds agglomerate into drops of rain are not yet
understood, and that opinions differ on this subject. Experiments to
decide the question are needed, and it is to be hoped that the Weather
Bureau will undertake them. For anything we know to the contrary, the
agglomeration may be facilitated by smoke in the air. If it be really
true that rains have been produced by great battles, we may say with
confidence that they were produced by the smoke from the burning powder
rising into the clouds and forming nuclei for the agglomeration into
drops, and not by th