em, they may do so.

"What would happen to a metal bar if all the molecules in it decided to
move in the same direction at the same time? Their heat motion is
normally carrying them about at a rate of several miles a second, and if
now we have them all go in one way, the entire bar must move in that
direction, and it will start off at a velocity as great as the velocity
of the individual molecules. But now, if we attach the bar to a heavy
car, it will try to start off, but will be forced to drag the car with
it, and so will not be able to have its molecules moving at the same
rate. They will be slowed down in starting the mass of the car. But
slowly moving molecules have a definite physical significance. Molecules
move because of temperature, and lack of motion means lack of heat.
These molecules that have been slowed down are then cold; they will
absorb heat from the air about them, and since the molecule of hydrogen
gas at room temperature is moving at about seven miles a second, when
the molecules of the confined gas in our car, or the molecules of the
metal bar are slowed down to but a few hundred miles an hour, their
temperature drops to some hundreds of degrees below zero, and they
absorb energy very rapidly, for the greater the difference in
temperature, the greater the rate of heat absorption.

"I believe we will be able to accelerate the car rapidly to a speed of
several miles a second at very high altitudes, and as we will be able to
use a perfectly enclosed streamlined car, we should get tremendous
speeds. We'll need no wings, of course, for with a small unit pointed
vertically, we'll be able to support the car in the air. It will make
possible a machine that will be able to fly in reverse and so come to a
quick stop. It will steer us or it will supply us with electrical power,
for we merely have to put a series of small metal bars about the
circumference of the generator, and get a tremendously powerful engine.

"For our present need, it means a tremendously powerful engine--and one
that we can make invisible.

"I believe you can guess the source of that breeze we had there? It
would make a wonderful air-conditioning unit."

"Dick Arcot," began Morey, his voice tight with suppressed excitement,
"I would like to be able to use this invention. I know enough of the
economics of the thing, if not its science, to know that the apparatus
before us is absolutely invaluable. I couldn't afford to buy the rights