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Chapter 7


CHAPTER VII


THE HYMN OF THE CANNON-BALL


The Observatory of Cambridge in its memorable letter had treated the
question from a purely astronomical point of view. The mechanical
part still remained.

President Barbicane had, without loss of time, nominated a
working committee of the Gun Club. The duty of this committee
was to resolve the three grand questions of the cannon, the
projectile, and the powder. It was composed of four members of
great technical knowledge, Barbicane (with a casting vote in
case of equality), General Morgan, Major Elphinstone, and J. T.
Maston, to whom were confided the functions of secretary. On the
8th of October the committee met at the house of President
Barbicane, 3 Republican Street. The meeting was opened by the
president himself.

"Gentlemen," said he, "we have to resolve one of the most
important problems in the whole of the noble science of gunnery.
It might appear, perhaps, the most logical course to devote our
first meeting to the discussion of the engine to be employed.
Nevertheless, after mature consideration, it has appeared to me
that the question of the projectile must take precedence of that
of the cannon, and that the dimensions of the latter must
necessarily depend on those of the former."

"Suffer me to say a word," here broke in J. T. Maston.
Permission having been granted, "Gentlemen," said he with an
inspired accent, "our president is right in placing the question
of the projectile above all others. The ball we are about to
discharge at the moon is our ambassador to her, and I wish to
consider it from a moral point of view. The cannon-ball,
gentlemen, to my mind, is the most magnificent manifestation of
human power. If Providence has created the stars and the planets,
man has called the cannon-ball into existence. Let Providence
claim the swiftness of electricity and of light, of the stars,
the comets, and the planets, of wind and sound-- we claim to
have invented the swiftness of the cannon-ball, a hundred times
superior to that of the swiftest horses or railway train.
How glorious will be the moment when, infinitely exceeding all
hitherto attained velocities, we shall launch our new projectile
with the rapidity of seven miles a second! Shall it not,
gentlemen-- shall it not be received up there with the honors
due to a terrestrial ambassador?"

Overcome with emotion the orator sat down and applied himself to
a huge plate of sandwiches before him.

"And now," said Barbicane, "let us quit the domain of poetry and
come direct to the question."

"By all means," replied the members, each with his mouth full
of sandwich.

"The problem before us," continued the president, "is how to
communicate to a projectile a velocity of 12,000 yards per second.
Let us at present examine the velocities hitherto attained.
General Morgan will be able to enlighten us on this point."

"And the more easily," replied the general, "that during the war
I was a member of the committee of experiments. I may say,
then, that the 100-pounder Dahlgrens, which carried a distance
of 5,000 yards, impressed upon their projectile an initial
velocity of 500 yards a second. The Rodman Columbiad threw a
shot weighing half a ton a distance of six miles, with a
velocity of 800 yards per second-- a result which Armstrong and
Palisser have never obtained in England."

"This," replied Barbicane, "is, I believe, the maximum velocity
ever attained?"

"It is so," replied the general.

"Ah!" groaned J. T. Maston, "if my mortar had not burst----"

"Yes," quietly replied Barbicane, "but it did burst. We must
take, then, for our starting point, this velocity of 800 yards.
We must increase it twenty-fold. Now, reserving for another
discussion the means of producing this velocity, I will call
your attention to the dimensions which it will be proper to
assign to the shot. You understand that we have nothing to do
here with projectiles weighing at most but half a ton."

"Why not?" demanded the major.

"Because the shot," quickly replied J. T. Maston, "must be big
enough to attract the attention of the inhabitants of the moon,
if there are any?"

"Yes," replied Barbicane, "and for another reason more important still."

"What mean you?" asked the major.

"I mean that it is not enough to discharge a projectile, and
then take no further notice of it; we must follow it throughout
its course, up to the moment when it shall reach its goal."

"What?" shouted the general and the major in great surprise.

"Undoubtedly," replied Barbicane composedly, "or our experiment
would produce no result."

"But then," replied the major, "you will have to give this
projectile enormous dimensions."

"No! Be so good as to listen. You know that optical
instruments have acquired great perfection; with certain
instruments we have succeeded in obtaining enlargements of 6,000
times and reducing the moon to within forty miles' distance.
Now, at this distance, any objects sixty feet square would be
perfectly visible.

"If, then, the penetrative power of telescopes has not been
further increased, it is because that power detracts from their
light; and the moon, which is but a reflecting mirror, does not
give back sufficient light to enable us to perceive objects of
lesser magnitude."

"Well, then, what do you propose to do?" asked the general.
"Would you give your projectile a diameter of sixty feet?"

"Not so."

"Do you intend, then, to increase the luminous power of the moon?"

"Exactly so. If I can succeed in diminishing the density of the
atmosphere through which the moon's light has to travel I shall
have rendered her light more intense. To effect that object it
will be enough to establish a telescope on some elevated mountain.
That is what we will do."

"I give it up," answered the major. "You have such a way of
simplifying things. And what enlargement do you expect to
obtain in this way?"

"One of 48,000 times, which should bring the moon within an
apparent distance of five miles; and, in order to be visible,
objects need not have a diameter of more than nine feet."

"So, then," cried J. T. Maston, "our projectile need not be more
than nine feet in diameter."

"Let me observe, however," interrupted Major Elphinstone, "this
will involve a weight such as----"

"My dear major," replied Barbicane, "before discussing its
weight permit me to enumerate some of the marvels which our
ancestors have achieved in this respect. I don't mean to
pretend that the science of gunnery has not advanced, but it
is as well to bear in mind that during the middle ages they
obtained results more surprising, I will venture to say, than ours.
For instance, during the siege of Constantinople by Mahomet II.,
in 1453, stone shot of 1,900 pounds weight were employed. At Malta,
in the time of the knights, there was a gun of the fortress of St.
Elmo which threw a projectile weighing 2,500 pounds. And, now,
what is the extent of what we have seen ourselves? Armstrong guns
discharging shot of 500 pounds, and the Rodman guns projectiles
of half a ton! It seems, then, that if projectiles have gained
in range, they have lost far more in weight. Now, if we turn our
efforts in that direction, we ought to arrive, with the progress
on science, at ten times the weight of the shot of Mahomet II.
and the Knights of Malta."

"Clearly," replied the major; "but what metal do you calculate
upon employing?"

"Simply cast iron," said General Morgan.

"But," interrupted the major, "since the weight of a shot is
proportionate to its volume, an iron ball of nine feet in
diameter would be of tremendous weight."

"Yes, if it were solid, not if it were hollow."

"Hollow? then it would be a shell?"

"Yes, a shell," replied Barbicane; "decidely it must be. A solid
shot of 108 inches would weigh more than 200,000 pounds, a weight
evidently far too great. Still, as we must reserve a certain
stability for our projectile, I propose to give it a weight of
20,000 pounds."

"What, then, will be the thickness of the sides?" asked the major.

"If we follow the usual proportion," replied Morgan, "a diameter
of 108 inches would require sides of two feet thickness, or less."

"That would be too much," replied Barbicane; "for you will
observe that the question is not that of a shot intended to
pierce an iron plate; it will suffice to give it sides strong
enough to resist the pressure of the gas. The problem,
therefore, is this-- What thickness ought a cast-iron shell to
have in order not to weight more than 20,000 pounds? Our clever
secretary will soon enlighten us upon this point."

"Nothing easier." replied the worthy secretary of the committee;
and, rapidly tracing a few algebraical formulae upon paper,
among which _n_^2 and _x_^2 frequently appeared, he presently said:

"The sides will require a thickness of less than two inches."

"Will that be enough?" asked the major doubtfully.

"Clearly not!" replied the president.

"What is to be done, then?" said Elphinstone, with a puzzled air.

"Employ another metal instead of iron."

"Copper?" said Morgan.

"No! that would be too heavy. I have better than that to offer."

"What then?" asked the major.

"Aluminum!" replied Barbicane.

"Aluminum?" cried his three colleagues in chorus.

"Unquestionably, my friends. This valuable metal possesses the
whiteness of silver, the indestructibility of gold, the tenacity
of iron, the fusibility of copper, the lightness of glass. It is
easily wrought, is very widely distributed, forming the base of
most of the rocks, is three times lighter than iron, and seems to
have been created for the express purpose of furnishing us with
the material for our projectile."

"But, my dear president," said the major, "is not the cost price
of aluminum extremely high?"

"It was so at its first discovery, but it has fallen now to nine
dollars a pound."

"But still, nine dollars a pound!" replied the major, who was
not willing readily to give in; "even that is an enormous price."

"Undoubtedly, my dear major; but not beyond our reach."

"What will the projectile weigh then?" asked Morgan.

"Here is the result of my calculations," replied Barbicane.
"A shot of 108 inches in diameter, and twelve inches in
thickness, would weigh, in cast-iron, 67,440 pounds; cast in
aluminum, its weight will be reduced to 19,250 pounds."

"Capital!" cried the major; "but do you know that, at nine
dollars a pound, this projectile will cost----"

"One hundred and seventy-three thousand and fifty dollars ($173,050).
I know it quite well. But fear not, my friends; the money will not
be wanting for our enterprise. I will answer for it. Now what say
you to aluminum, gentlemen?"

"Adopted!" replied the three members of the committee. So ended
the first meeting. The question of the projectile was
definitely settled.

Jules Verne

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