pick a flaw in it.

"If that same bar magnet were held in the field of the electromagnet
with its north pole pointed toward the magnet and then, by the action of
some outside force of sufficient power, its polarity were reversed, the
bar would be repelled. If the magnetism were neutralized and held
exactly neutral, it would be neither repelled nor attracted, but would
act only as the force of gravity impelled it. Is that clear?"

"Perfectly," I assented.

"That, then, paves the way for what I have to tell you. I have
developed an electrical method of neutralizing the gravity of a body
while it is within the field of the earth, and also, by a slight
extension, a method of entirely reversing its polarity."

* * * * *

I nodded calmly.

"Do you realize what this means?" he cried.

"No," I replied, puzzled by his great excitement.

"Man alive," he cried, "it means that the problem of aerial flight is
entirely revolutionized, and that the era of interplanetary travel is at
hand! Suppose that I construct an airship and then render it neutral to
gravity. It would weigh nothing, _absolutely nothing_! The tiniest
propeller would drive it at almost incalculable speed with a minimum
consumption of power, for the only resistance to its motion would be the
resistance of the air. If I were to reverse the polarity, it would be
repelled from the earth with the same force with which it is now
attracted, and it would rise with the same acceleration as a body falls
toward the earth. It would travel to the moon in two hours and forty
minutes."

"Air resistance would--"

"There is no air a few miles from the earth. Of course, I do not mean
that such a craft would take off from the earth and land on the moon
three hours later. There are two things which would interfere with that.
One is the fact that the propelling force, the gravity of the earth,
would diminish as the square of the distance from the center of the
earth, and the other is that when the band of neutral attraction, or
rather repulsion, between the earth and the moon had been reached, it
would be necessary to decelerate so as to avoid a smash on landing. I
have been over the whole thing and I find that it would take twenty-nine
hours and fifty-two minutes to make the whole trip. The entire thing is
perfectly possible. In fact, I have asked you here to witness and report
the first interplanetary trip to be made."

"Have you constructed