an instant, though constantly renewed, and its explosive impulse
cannot carry its light products of combustion very far through
stationary and resistant air. It is _the induction of air_ carried
with it by such semi-explosive impulse (under proper mechanical
conditions) that is strange to our observation and understanding, and
is the second factor in the phenomenon we are accounting for and
preparing to utilize.

The process, as it actually is, may be clearly exhibited by a very
simple means. Let anyone take a tube, say an inch in diameter--a roll
of paper will do as well as anything--and, applying it closely to his
mouth, try the whole force of his lungs through it upon any light
object. The amount of effect will be found surprisingly small; and
unless the tube is a short one, it will be so far absorbed by friction
and atmospheric resistance as to be almost imperceptible. Then let him
hold the same tube near to the mouth, but not in contact, and repeat
the experiment. With the best adjustment, the effect may be described
as tenfold or fifty-fold, or almost any fold--the effect of the simple
blowing being merely nominal as compared with the induced current
added by blowing _into_ the tube instead of _in_ it. The blast enters
the free and open orifice with all the contiguous air which its
surface friction and the vacuum of its movement can involve in its
rolling vortex. While the entrance is thus crowded with pressure, the
exit is free; and the result at the exit is a blast of well sustained
velocity and _magnified volume;_ ready itself to repeat the miracle on
a still larger scale if provided with the apparatus for doing so. To
test this, now place a second and larger tube in such position as to
prolong the first in a straight line, but with a slight interval
between the meeting ends; so that the blast, as magnified in volume in
entering the first tube, may enter in like manner the second tube and