HISTORY OF THE CANNON.
The resolutions passed at this meeting produced a
great effect outside. Some timid people grew
alarmed at the idea of a projectile weighing 20,000
lbs. hurled into space. People asked what cannon
could ever transmit an initial speed sufficient for
such a mass. The report of the second meeting
was destined to answer these questions victoriously.
The next evening the four members of the Gun Club
sat down before fresh mountains of sandwiches and
a veritable ocean of tea. The debate then began.
“My dear colleagues,” said Barbicane,
“we are going to occupy ourselves with the construction
of the engine, its length, form, composition, and
weight. It is probable that we shall have to give
it gigantic dimensions, but, however great our difficulties
might be, our industrial genius will easily overcome
them. Will you please listen to me and spare
objections for the present? I do not fear them.”
An approving murmur greeted this declaration.
“We must not forget,” resumed Barbicane,
“to what point our yesterday’s debate
brought us; the problem is now the following:
how to give an initial speed of 12,000 yards a second
to a shot 108 inches in diameter weighing 20,000 lbs.
“That is the problem indeed,” answered
Major Elphinstone.
“When a projectile is hurled into space,”
resumed Barbicane, “what happens? It is
acted upon by three independent forces, the resistance
of the medium, the attraction of the earth, and the
force of impulsion with which it is animated.
Let us examine these three forces. The resistance
of the medium—that is to say, the resistance
of the air—is of little importance.
In fact, the terrestrial atmosphere is only forty miles
deep. With a rapidity of 12,000 yards the projectile
will cross that in five seconds, and this time will
be short enough to make the resistance of the medium
insignificant. Let us now pass to the attraction
of the earth—that is to say, to the weight
of the projectile. We know that that weight diminishes
in an inverse ratio to the square of distances—in
fact, this is what physics teach us: when a body
left to itself falls on the surface of the earth,
it falls 15 feet in the first second, and if the same
body had to fall 257,542 miles—that is to
say, the distance between the earth and the moon—its
fall would be reduced to half a line in the first
second. That is almost equivalent to immobility.
The question is, therefore, how progressively to overcome
this law of gravitation. How shall we do it?
By the force of impulsion?”
“That is the difficulty,” answered the
major.
“That is it indeed,” replied the president.
“But we shall triumph over it, for this force
of impulsion we want depends on the length of the
engine and the quantity of powder employed, the one
only being limited by the resistance of the other.
Let us occupy ourselves, therefore, to-day with the
dimensions to be given to the cannon. It is quite
understood that we can make it, as large as we like,
seeing it will not have to be moved.”
