CHAPTER VII
THE HYMN OF THE CANNON-BALL
The Observatory of Cambridge in its memorable letter had treated thequestion from a purely astronomical point of view. The mechanicalpart still remained.
President Barbicane had, without loss of time, nominated aworking committee of the Gun Club. The duty of this committeewas to resolve the three grand questions of the cannon, theprojectile, and the powder. It was composed of four members ofgreat technical knowledge, Barbicane (with a casting vote incase of equality), General Morgan, Major Elphinstone, and J. T.Maston, to whom were confided the functions of secretary. On the8th of October the committee met at the house of PresidentBarbicane, 3 Republican Street. The meeting was opened by thepresident himself.
"Gentlemen," said he, "we have to resolve one of the mostimportant problems in the whole of the noble science of gunnery.It might appear, perhaps, the most logical course to devote ourfirst meeting to the discussion of the engine to be employed.Nevertheless, after mature consideration, it has appeared to methat the question of the projectile must take precedence of thatof the cannon, and that the dimensions of the latter mustnecessarily 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 aninspired accent, "our president is right in placing the questionof the projectile above all others. The ball we are about todischarge at the moon is our ambassador to her, and I wish toconsider it from a moral point of view. The cannon-ball,gentlemen, to my mind, is the most magnificent manifestation ofhuman power. If Providence has created the stars and the planets,man has called the cannon-ball into existence. Let Providenceclaim the swiftness of electricity and of light, of the stars,the comets, and the planets, of wind and sound-- we claim tohave invented the swiftness of the cannon-ball, a hundred timessuperior to that of the swiftest horses or railway train.How glorious will be the moment when, infinitely exceeding allhitherto attained velocities, we shall launch our new projectilewith the rapidity of seven miles a second! Shall it not,gentlemen-- shall it not be received up there with the honorsdue to a terrestrial ambassador?"
Overcome with emotion the orator sat down and applied himself toa huge plate of sandwiches before him.
"And now," said Barbicane, "let us quit the domain of poetry andcome direct to the question."
"By all means," replied the members, each with his mouth fullof sandwich.
"The problem before us," continued the president, "is how tocommunicate 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 warI was a member of the committee of experiments. I may say,then, that the 100-pounder Dahlgrens, which carried a distanceof 5,000 yards, impressed upon their projectile an initialvelocity of 500 yards a second. The Rodman Columbiad threw ashot weighing half a ton a distance of six miles, with avelocity of 800 yards per second-- a result which Armstrong andPalisser have never obtained in England."
"This," replied Barbicane, "is, I believe, the maximum velocityever 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 musttake, then, for our starting point, this velocity of 800 yards.We must increase it twenty-fold. Now, reserving for anotherdiscussion the means of producing this velocity, I will callyour attention to the dimensions which it will be proper toassign to the shot. You understand that we have nothing to dohere with projectiles weighing at most but half a ton."
"Why not?" demanded the major.
"Because the shot," quickly replied J. T. Maston, "must be bigenough 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, andthen take no further notice of it; we must follow it throughoutits 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 experimentwould produce no result."
"But then," replied the major, "you will have to give thisprojectile enormous dimensions."
"No! Be so good as to listen. You know that opticalinstruments have acquired great perfection; with certaininstruments we have succeeded in obtaining enlargements of 6,000times and reducing the moon to within forty miles' distance.Now, at this distance, any objects sixty feet square would beperfectly visible.
"If, then, the penetrative power of telescopes has not beenfurther increased, it is because that power detracts from theirlight; and the moon, which is but a reflecting mirror, does notgive back sufficient light to enable us to perceive objects oflesser 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 theatmosphere through which the moon's light has to travel I shallhave rendered her light more intense. To effect that object itwill 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 ofsimplifying things. And what enlargement do you expect toobtain in this way?"
"One of 48,000 times, which should bring the moon within anapparent 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 morethan nine feet in diameter."
"Let me observe, however," interrupted Major Elphinstone, "thiswill involve a weight such as----"
"My dear major," replied Barbicane, "before discussing itsweight permit me to enumerate some of the marvels which ourancestors have achieved in this respect. I don't mean topretend that the science of gunnery has not advanced, but itis as well to bear in mind that during the middle ages theyobtained 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 gunsdischarging shot of 500 pounds, and the Rodman guns projectilesof half a ton! It seems, then, that if projectiles have gainedin range, they have lost far more in weight. Now, if we turn ourefforts in that direction, we ought to arrive, with the progresson 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 calculateupon employing?"
"Simply cast iron," said General Morgan.
"But," interrupted the major, "since the weight of a shot isproportionate to its volume, an iron ball of nine feet indiameter 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 solidshot of 108 inches would weigh more than 200,000 pounds, a weightevidently far too great. Still, as we must reserve a certainstability for our projectile, I propose to give it a weight of20,000 pounds."
"What, then, will be the thickness of the sides?" asked the major.
"If we follow the usual proportion," replied Morgan, "a diameterof 108 inches would require sides of two feet thickness, or less."
"That would be too much," replied Barbicane; "for you willobserve that the question is not that of a shot intended topierce an iron plate; it will suffice to give it sides
strongenough to resist the pressure of the gas. The problem,therefore, is this-- What thickness ought a cast-iron shell tohave in order not to weight more than 20,000 pounds? Our cleversecretary 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 thewhiteness of silver, the indestructibility of gold, the tenacityof iron, the fusibility of copper, the lightness of glass. It iseasily wrought, is very widely distributed, forming the base ofmost of the rocks, is three times lighter than iron, and seems tohave been created for the express purpose of furnishing us withthe material for our projectile."
"But, my dear president," said the major, "is not the cost priceof aluminum extremely high?"
"It was so at its first discovery, but it has fallen now to ninedollars a pound."
"But still, nine dollars a pound!" replied the major, who wasnot 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 inthickness, would weigh, in cast-iron, 67,440 pounds; cast inaluminum, its weight will be reduced to 19,250 pounds."
"Capital!" cried the major; "but do you know that, at ninedollars 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 notbe wanting for our enterprise. I will answer for it. Now what sayyou to aluminum, gentlemen?"
"Adopted!" replied the three members of the committee. So endedthe first meeting. The question of the projectile wasdefinitely settled.