for a hearing. Now he seemed to feel that his opportunity had come,
for he continued with growing enthusiasm:--

"Hitherto all attempts at space travelling have been too timid or
puerile. We have experimented at aerial navigation, as if the brief span
of air were a step in the mighty distance which separates us from our
sister planets. As well might steamboats have been invented to cross
narrow streams, and never have ventured on the mighty ocean! We have
tried to imitate the bird, the kite, and the balloon, and our
experiments have failed, and always must, so long as we do not look
farther and think deeper. Every Icarus who attempts to overcome the
force of gravity, which conquers planets, and propel himself through the
air by any sort of apparatus, will always finish the trip with a wiser
but badly bruised head."

"Still, it has been freely predicted," I ventured, "that this century
will not close without the invention of a successful air-travelling
machine."

"And I alone have hit upon the right plan, because I have not attempted
to _struggle against_ gravity, but have made use of it only for
propelling my projectile!" exclaimed the doctor triumphantly.

"But wait!" I interposed. "Gravity acts only in one direction, and that
is exactly opposite to the one you propose to travel."

"That brings me to the very important discovery I made in physics two
years ago, upon which the whole success of the projectile rests. You
will remember that, according to the text-books, very little is known
about gravity except the laws of its action. What it is, and how it can
be controlled or modified, have never been known. Electricity was as
much a mystery fifty years ago, but we know all its attributes. We can
make it, store it, control it, and use it for almost every necessity of
life. The era of electricity is in full bloom, but the era of
gravitational force is just budding."

"Can it be that we have as much to learn from gravity as electricity has
taught us in the last half-century?" I exclaimed, as my eyes began to
open.

"I believe it will teach us far more wonderful things, because it will
take us to unknown worlds, while electricity has been confined to Earth.
Its realm is the wide universe. It will show us what life there is on
the planets. It will make us at home with the stars.

"What!" he continued in a sort of ecstasy. "Do you think all great
discoveries are over, all wonderful inventions made? As well might a
t