The Moon-Voyage. Jules VerneЧитать онлайн книгу.
adopted," answered the members of the committee.
"One question," said Elphinstone, "and will this canobusomortar be rifled?"
"No," answered Barbicane. "No, we must have an enormous initial speed, and you know very well that a shot leaves a rifle less rapidly than a smooth-bore."
"True," answered the major.
"Well, we have it this time," repeated J.T. Maston.
"Not quite yet," replied the president.
"Why not?"
"Because we do not yet know of what metal it will be made."
"Let us decide that without delay."
"I was going to propose it to you."
The four members of the committee each swallowed a dozen sandwiches, followed by a cup of tea, and the debate recommenced.
"Our cannon," said Barbicane, "must be possessed of great tenacity, great hardness; it must be infusible by heat, indissoluble, and inoxydable by the corrosive action of acids."
"There is no doubt about that," answered the major, "and as we shall have to employ a considerable quantity of metal we shall not have much choice."
"Well, then," said Morgan, "I propose for the fabrication of the Columbiad the best alloy hitherto known—that is to say, 100 parts of copper, 12 of tin, and 6 of brass."
"My friends," answered the president, "I agree that this composition has given excellent results; but in bulk it would be too dear and very hard to work. I therefore think we must adopt an excellent material, but cheap, such as cast-iron. Is not that your opinion, major?"
"Quite," answered Elphinstone.
"In fact," resumed Barbicane, "cast-iron costs ten times less than bronze; it is easily melted, it is readily run into sand moulds, and is rapidly manipulated; it is, therefore, an economy of money and time. Besides, that material is excellent, and I remember that during the war at the siege of Atlanta cast-iron cannon fired a thousand shots each every twenty minutes without being damaged by it."
"Yet cast-iron is very brittle," answered Morgan.
"Yes, but it possesses resistance too. Besides, we shall not let it explode, I can answer for that."
"It is possible to explode and yet be honest," replied J.T. Maston sententiously.
"Evidently," answered Barbicane. "I am, therefore, going to beg our worthy secretary to calculate the weight of a cast-iron cannon 900 feet long, with an inner diameter of nine feet, and sides six feet thick."
"At once," answered J.T. Maston, and, as he had done the day before, he made his calculations with marvellous facility, and said at the end of a minute—
"This cannon will weigh 68,040 tons."
"And how much will that cost at two cents a pound?"
"Two million five hundred and ten thousand seven hundred and one dollars."
J.T. Maston, the major, and the general looked at Barbicane anxiously.
"Well, gentlemen," said the president, "I can only repeat what I said to you yesterday, don't be uneasy; we shall not want for money."
Upon this assurance of its president the committee broke up, after having fixed a third meeting for the next evening.
CHAPTER IX.
THE QUESTION OF POWDERS.
The question of powder still remained to be settled. The public awaited this last decision with anxiety. The size of the projectile and length of the cannon being given, what would be the quantity of powder necessary to produce the impulsion? This terrible agent, of which, however, man has made himself master, was destined to play a part in unusual proportions.
It is generally known and often asserted that gunpowder was invented in the fourteenth century by the monk Schwartz, who paid for his great discovery with his life. But it is nearly proved now that this story must be ranked among the legends of the Middle Ages. Gunpowder was invented by no one; it is a direct product of Greek fire, composed, like it, of sulphur and saltpetre; only since that epoch these mixtures; which were only dissolving, have been transformed into detonating mixtures.
But if learned men know perfectly the false history of gunpowder, few people are aware of its mechanical power. Now this is necessary to be known in order to understand the importance of the question submitted to the committee.
Thus a litre of gunpowder weighs about 2 lbs.; it produces, by burning, about 400 litres of gas; this gas, liberated, and under the action of a temperature of 2,400°, occupies the space of 4,000 litres. Therefore the volume of powder is to the volume of gas produced by its deflagration as 1 to 400. The frightful force of this gas, when it is compressed into a space 4,000 times too small, may be imagined.
This is what the members of the committee knew perfectly when, the next day, they began their sitting. Major Elphinstone opened the debate.
"My dear comrades," said the distinguished chemist, "I am going to begin with some unexceptionable figures, which will serve as a basis for our calculation. The 24-lb. cannon-ball, of which the Hon. J.T. Maston spoke the day before yesterday, is driven out of the cannon by 16 lbs. of powder only."
"You are certain of your figures?" asked Barbicane.
"Absolutely certain," answered the major. "The Armstrong cannon only uses 75 lbs. of powder for a projectile of 800 lbs., and the Rodman Columbiad only expends 160 lbs. of powder to send its half-ton bullet six miles. These facts cannot be doubted, for I found them myself in the reports of the Committee of Artillery."
"That is certain," answered the general.
"Well," resumed the major, "the conclusion to be drawn from these figures is that the quantity of powder does not augment with the weight of the shot; in fact, if a shot of 24 lbs. took 16 lbs. of powder, and, in other terms, if in ordinary cannons a quantity of powder weighing two-thirds of the weight of the projectile is used, this proportion is not always necessary. Calculate, and you will see that for the shot of half a ton weight, instead of 333 lbs. of powder, this quantity has been reduced to 116 lbs. only.
"What are you driving at?" asked the president.
"The extreme of your theory, my dear major," said J.T. Maston, "would bring you to having no powder at all, provided your shot were sufficiently heavy."
"Friend Maston will have his joke even in the most serious things," replied the major; "but he need not be uneasy; I shall soon propose a quantity of powder that will satisfy him. Only I wish to have it understood that during the war, and for the largest guns, the weight of the powder was reduced, after experience, to a tenth of the weight of the shot."
"Nothing is more exact," said Morgan; "but, before deciding the quantity of powder necessary to give the impulsion, I think it would be well to agree upon its nature."
"We shall use a large-grained powder," answered the major; "its deflagration is the most rapid."
"No doubt," replied Morgan; "but it is very brittle, and ends by damaging the chamber of the gun."
"Certainly; but what would be bad for a gun destined for long service would not be so for our Columbiad. We run no danger of explosion, and the powder must immediately take fire to make its mechanical effect complete."
"We might make several touchholes," said J.T. Maston, "so as to set fire to it in several places at the same time."
"No doubt," answered Elphinstone, "but that would make the working of it more difficult. I therefore come back to my large-grained powder that removes these difficulties."
"So