A Trip to Venus | Page 6

us from another world, except on the wings of the
imagination?"
I. "Great discoveries and inventions are born of dreams. There are minds which can
foresee what lies before us, and the march of science brings it within our reach. All or
nearly all our great scientific victories have been foretold, and they have generally been
achieved by more than one person when the time came. The telescope was a dream for
ages, so was the telephone, steam and electric locomotion, aerial navigation. Why should
we scout the dream of visiting other worlds, which is at least as old as Lucian? Ere long,
and perhaps before the century is out, we shall be flying through the air to the various
countries of the globe. In succeeding centuries what is to hinder us from travelling
through space to different planets?"
G. "Quite impossible. Consider the tremendous distance--the lifeless vacuum--that
separates us even from the moon. Two hundred and forty thousand miles of empty
space."
I. "Some ten times round the world. Well, is that tremendous vacuum absolutely
impassable?"
G. "To any but Jules Verne and his hero, the illustrious Barbicane, president of the Gun
Club."[1]
[Footnote 1: _The Voyage à la Lune_, by Jules Verne.]
I. "Jules Verne has an original mind, and his ideas, though extravagant, are not without
value. Some of them have been realised, and it may be worth while to examine his notion
of firing a shot from the earth to the moon. The projectile, if I remember, was an
aluminium shell in the shape of a conical bullet, and contained three men, a dog or two,
and several fowls, together with provisions and instruments. It was air tight, warmed and
illuminated with coal gas, and the oxygen for breathing was got from chlorate of potash,
while the carbonic acid produced by the lungs and gas-burners was absorbed with caustic
potash to keep the air pure. This bullet-car was fired from a colossal cast-iron gun
founded in the sand. It was aimed at a point in the sky, the zenith, in fact, where it would
strike the moon four days later, that is, after it had crossed the intervening space. The
charge of gun-cotton was calculated to give the projectile a velocity sufficient to carry it
past the 'dead-point,' where the gravity of the earth upon it was just balanced by that of
the moon, and enable it to fall towards the moon for the rest of the way. The sudden
shock of the discharge on the car and its occupants was broken by means of spring
buffers and water pressure."

G. "The last arrangement was altogether inadequate."
I. "It was certainly a defect in the scheme."
G. "Besides, the initial velocity of the bullet to carry it beyond the 'dead-point,' was, I
think, 12,000 yards a second, or something like seven miles a second."
I. "His estimate was too high. An initial velocity of 9,000 yards, or five miles a second,
would carry a projectile beyond the sensible attraction of the earth towards the moon, the
planets, or anywhere; in short, to an infinite distance. Indeed, a slightly lower velocity
would suffice in the case of the moon, owing to her attraction."
G. "But how are we to give the bullet that velocity? I believe the highest velocity
obtained from a single discharge of cordite, one of our best explosives, was rather less
than 4,000 feet, or only about three-quarters of a mile per second. With such a velocity,
the projectile would simply rise to a great height and then fall back to the ground."
I. "Both of these drawbacks can be overcome. We are not limited to a single discharge.
Dr. S. Tolver Preston, the well-known writer on molecular science, has pointed out that a
very high velocity can be got by the use of a compound gun, or, in other words, a gun
which fires another gun as a projectile.[2] Imagine a first gun of enormous dimensions
loaded with a smaller gun, which in turn is loaded with the bullet. The discharge of the
first gun shoots the second gun into the air, with a certain velocity. If, now, the second
gun, at the instant it leaves the muzzle of the first, is fired automatically, say by utilising
the first discharge to press a spring which can react on a hammer or needle, the bullet will
acquire a velocity due to both discharges, and equivalent to the velocity of the second gun
at the time it was fired plus the velocity produced by the explosion of its own charge. In
this way, by employing a series of guns, fired from each other in succession, we can
graduate the starting shock, and give the bullet a final velocity sufficient to raise it against
gravity,