of seven miles a second! Shall it not, gentlemen – shall it not be received up there with the honours 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 5000 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 telescopes we have succeeded in obtaining enlargements of 6000 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 1900 lbs. 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 2500 lbs. And, now, what is the extent of what we have seen ourselves? Armstrong guns discharging shot of 500 lbs., 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 of 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; "decidedly it must be. A solid shot of 108 inches would weigh more than 200,000 lbs., 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 lbs."
"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, therefore, 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 weigh more than 20,000 lbs.? 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 formulæ upon paper, among which n² and x² 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.
"Aluminium!"
