cannon of Dahlgren, with a range of 5,000 yards, gave their projectiles an initial speed of 500 yards a second.”
“Yes; and the Rodman Columbiad?” (the Americans gave the name of “Columbiad” to their enormous engines of destruction) asked the president.
“The Rodman Columbiad, tried at Fort Hamilton, near New York, hurled a projectile, weighing half a ton, a distance of six miles, with a speed of 800 yards a second, a result which neither Armstrong nor Palliser has obtained in England.”
“Englishmen are nowhere!” said J.T. Maston, pointing his formidable steel hook eastward.
“Then,” resumed Barbicane, “a speed of 800 yards is the maximum obtained at present.”
“Yes,” answered Morgan.
“I might add, however,” replied J.T. Maston, “that if my mortar had not been blown up—”
“Yes, but it was blown up,” replied Barbicane with a benevolent gesture. “We must take the speed of 800 yards for a starting point. We must keep till another meeting the discussion of the means used to produce this speed; allow me to call your attention to the dimensions which our projectile must have. Of course it must be something very different to one of half a ton weight.”
“Why?” asked the major.
“Because,” quickly answered J.T. Maston, “it must be large enough to attract the attention of the inhabitants of the moon, supposing there are any.”
“Yes,” answered Barbicane, “and for another reason still more important.”
“What do you mean, Barbicane?” asked the major.
“I mean that it is not enough to send up a projectile and then to think no more about it; we must follow it in its transit.”
“What?” said the general, slightly surprised at the proposition.
“Certainly,” replied Barbicane, like a man who knew what he was saying, “or our experiment will be without result.”
“But then,” replied the major, “you will have to give the projectile enormous dimensions.”
“No. Please grant me your attention. You know that optical instruments have acquired great perfection; certain telescopes increase objects six thousand, and bring the moon to within a distance of forty miles. Now at that distance objects sixty feet square are perfectly visible. The power of penetration of the telescope has not been increased, because that power is only exercised to the detriment of their clearness, and the moon, which is only a reflecting mirror, does not send a light intense enough for the telescopes to increase objects beyond that limit.”
“Very well, then, what do you mean to do?” asked the general. “Do you intend giving a diameter of sixty feet to your projectile?”
“No.”
“You are not going to take upon yourself the task of making the moon more luminous?”
“I am, though.”
“That’s rather strong!” exclaimed Maston.
“Yes, but simple,” answered Barbicane. “If I succeed in lessening the density of the atmosphere which the moon’s light traverses, shall I not render that light more intense?”
“Evidently.”
“In order to obtain that result I shall only have to establish my telescope upon some high mountain. We can do that.”
“I give in,” answered the major; “you have such a way of simplifying things! What enlargement do you hope to obtain thus?”
“One of 48,000 times, which will bring the moon within five miles only, and objects will only need a diameter of nine feet.”
“Perfect!” exclaimed J.T. Maston; “then our projectile will have a diameter of nine feet?”
“Precisely.”
“Allow me to inform you, however,” returned Major Elphinstone, “that its weight will still be—”
“Oh, major!” answered Barbicane, “before discussing its weight allow me to tell you that our forefathers did marvels in that way. Far be it from me to pretend that ballistics have not progressed, but it is well to know that in the Middle Ages surprising results were obtained, I dare affirm, even more surprising than ours.”
“Justify your statement,” exclaimed J.T. Maston.
“Nothing is easier,” answered Barbicane; “I can give you some examples. At the siege of Constantinople by Mahomet II., in 1453, they hurled stone bullets that weighed 1,900 lbs.; at Malta, in the time of its knights, a certain cannon of Fort Saint Elme hurled projectiles weighing 2,500 lbs. According to a French historian, under Louis XI. a mortar hurled a bomb of 500 lbs. only; but that bomb, fired at the Bastille, a place where mad men imprisoned wise ones, fell at Charenton, where wise men imprison mad ones.”
“Very well,” said J.T. Maston.
“Since, what have we seen, after all? The Armstrong cannons hurl projectiles of 500 lbs., and the Rodman Columbiads projectiles of half a ton! It seems, then, that if projectiles have increased in range they have lost in weight. Now, if we turn our efforts in that direction, we must succeed with the progress of the science in doubling the weight of the projectiles of Mahomet II. and the Knights of Malta.”
“That is evident,” answered the major; “but what metal do you intend to employ for your own projectile?”
“Simply cast-iron,” said General Morgan.
“Cast-iron!” exclaimed J.T. Maston disdainfully, “that’s very common for a bullet destined to go to the moon.”
“Do not let us exaggerate, my honourable friend,” answered Morgan; “cast-iron will be sufficient.”
“Then,” replied Major Elphinstone, “as the weight of the projectile is in proportion to its volume, a cast-iron bullet, measuring nine feet in diameter, will still be frightfully heavy.”
“Yes, if it be solid, but not if it be hollow,” said Barbicane.
“Hollow!—then it will be an obus?”
“In which we can put despatches,” replied J.T. Maston, “and specimens of our terrestrial productions.”
“Yes, an obus,” answered Barbicane; “that is what it must be; a solid bullet of 108 inches would weigh more than 200,000 lbs., a weight evidently too great; however, as it is necessary to give the projectile a certain stability, I propose to give it a weight of 20,000 lbs.”
“What will be the thickness of the metal?” asked the major.
“If we follow the usual proportions,” replied Morgan, “a diameter of 800 inches demands sides two feet thick at least.”
“That would be much too thick,” answered Barbicane; “we do not want a projectile to pierce armour-plate; it only needs sides strong enough to resist the pressure of the powder-gas. This, therefore, is the problem:—What thickness ought an iron obus to have in order to weigh only 20,000 lbs.? Our clever calculator, Mr. Maston, will tell us at once.”
“Nothing is easier,” replied the honourable secretary.
So saying, he traced some algebraical signs on the paper, amongst which n^2 and x^2 frequently appeared. He even seemed to extract from them a certain cubic root, and said—
“The sides must be hardly two inches thick.”
“Will that be sufficient?” asked the major doubtfully.
“No,” answered the president, “certainly not.”
“Then what must be done?” resumed Elphinstone, looking puzzled.
“We