The resolutions passed at the last meeting produced a great effect out of doors. Timid people took fright at the idea of a shot weighing 20,000 pounds being launched into space; they asked what cannon1 could ever transmit a sufficient velocity2 to such a mighty3 mass. The minutes of the second meeting were destined4 triumphantly5 to answer such questions. The following evening the discussion was renewed.
“My dear colleagues,” said Barbicane, without further preamble6, “the subject now before us is the construction of the engine, its length, its composition, and its weight. It is probable that we shall end by giving it gigantic dimensions; but however great may be the difficulties in the way, our mechanical genius will readily surmount7 them. Be good enough, then, to give me your attention, and do not hesitate to make objections at the close. I have no fear of them. The problem before us is how to communicate an initial force of 12,000 yards per second to a shell of 108 inches in diameter, weighing 20,000 pounds. Now when a projectile8 is launched into space, what happens to it? It is acted upon by three independent forces: the resistance of the air, the attraction of the earth, and the force of impulsion with which it is endowed. Let us examine these three forces. The resistance of the air is of little importance. The atmosphere of the earth does not exceed forty miles. Now, with the given rapidity, the projectile will have traversed this in five seconds, and the period is too brief for the resistance of the medium to be regarded otherwise than as insignificant9. Proceding, then, to the attraction of the earth, that is, the weight of the shell, we know that this weight will diminish in the inverse10 ratio of the square of the distance. When a body left to itself falls to the surface of the earth, it falls five feet in the first second; and if the same body were removed 257,542 miles further off, in other words, to the distance of the moon, its fall would be reduced to about half a line in the first second. That is almost equivalent to a state of perfect rest. Our business, then, is to overcome progressively this action of gravitation. The mode of accomplishing that is by the force of impulsion.”
“There’s the difficulty,” broke in the major.
“True,” replied the president; “but we will overcome that, for the force of impulsion will depend on the length of the engine and the powder employed, the latter being limited only by the resisting power of the former. Our business, then, to-day is with the dimensions of the cannon.”
“Now, up to the present time,” said Barbicane, “our longest guns have not exceeded twenty-five feet in length. We shall therefore astonish the world by the dimensions we shall be obliged to adopt. It must evidently be, then, a gun of great range, since the length of the piece will increase the detention11 of the gas accumulated behind the projectile; but there is no advantage in passing certain limits.”
“Quite so,” said the major. “What is the rule in such a case?”
“Ordinarily the length of a gun is twenty to twenty-five times the diameter of the shot, and its weight two hundred and thirty-five to two hundred and forty times that of the shot.”
“That is not enough,” cried J. T. Maston impetuously.
“I agree with you, my good friend; and, in fact, following this proportion for a projectile nine feet in diameter, weighing 30,000 pounds, the gun would only have a length of two hundred and twenty- five feet, and a weight of 7,200,000 pounds.”
“Ridiculous!” rejoined Maston. “As well take a pistol.”
“I think so too,” replied Barbicane; “that is why I propose to quadruple that length, and to construct a gun of nine hundred feet.”
The general and the major offered some objections; nevertheless, the proposition, actively12 supported by the secretary, was definitely adopted.
“But,” said Elphinstone, “what thickness must we give it?”
“A thickness of six feet,” replied Barbicane.
“You surely don’t think of mounting a mass like that upon a carriage?” asked the major.
“It would be a superb idea, though,” said Maston.
“But impracticable,” replied Barbicane. “No, I think of sinking this engine in the earth alone, binding13 it with hoops14 of wrought15 iron, and finally surrounding it with a thick mass of masonry16 of stone and cement. The piece once cast, it must be bored with great precision, so as to preclude17 any possible windage. So there will be no loss whatever of gas, and all the expansive force of the powder will be employed in the propulsion.”
“One simple question,” said Elphinstone: “is our gun to be rifled?”
“No, certainly not,” replied Barbicane; “we require an enormous initial velocity; and you are well aware that a shot quits a rifled gun less rapidly than it does a smooth-bore.”
“True,” rejoined the major.
The committee here adjourned18 for a few minutes to tea and sandwiches.
On the discussion being renewed, “Gentlemen,” said Barbicane, “we must now take into consideration the metal to be employed. Our cannon must be possessed19 of great tenacity20, great hardness, be infusible by heat, indissoluble, and inoxidable by the corrosive21 action of acids.”
“There is no doubt about that,” replied the major; “and as we shall have to employ an immense quantity of metal, we shall not be at a loss for choice.”
“Well, then,” said Morgan, “I propose the best alloy22 hitherto known, which consists of one hundred parts of copper23, twelve of tin, and six of brass24.”
“I admit,” replied the president, “that this composition has yielded excellent results, but in the present case it would be too expensive, and very difficult to work. I think, then, that we ought to adopt a material excellent in its way and of low price, such as cast iron. What is your advice, major?”
“I quite agree with you,” replied Elphinstone.
“In fact,” continued Barbicane, “cast iron costs ten times less than bronze; it is easy to cast, it runs readily from the moulds of sand, it is easy of manipulation, it is at once economical of money and of time. In addition, it is excellent as a material, and I well remember that during the war, at the siege of Atlanta, some iron guns fired one thousand rounds at intervals25 of twenty minutes without injury.”
“Cast iron is very brittle26, though,” replied Morgan.
“Yes, but it possesses great resistance. I will now ask our worthy27 secretary to calculate the weight of a cast-iron gun with a bore of nine feet and a thickness of six feet of metal.”
“In a moment,” replied Maston. Then, dashing off some algebraical formulae with marvelous facility, in a minute or two he declared the following result:
“The cannon will weigh 68,040 tons. And, at two cents a pound, it will cost ——”
“Two million five hundred and ten thousand seven hundred and one dollars.”
Maston, the major, and the general regarded Barbicane with uneasy looks.
“Well, gentlemen,” replied the president, “I repeat what I said yesterday. Make yourselves easy; the millions will not be wanting.”
With this assurance of their president the committee separated, after having fixed28 their third meeting for the following evening.
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cannon
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| n.大炮，火炮；飞机上的机关炮 | |
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velocity
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| n.速度，速率 | |
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mighty
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| adj.强有力的；巨大的 | |
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destined
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| adj.命中注定的；(for)以…为目的地的 | |
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triumphantly
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| ad.得意洋洋地；得胜地；成功地 | |
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preamble
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| n.前言；序文 | |
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surmount
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| vt.克服；置于…顶上 | |
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projectile
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| n.投射物，发射体；adj.向前开进的；推进的；抛掷的 | |
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insignificant
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| adj.无关紧要的，可忽略的，无意义的 | |
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inverse
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| adj.相反的，倒转的，反转的；n.相反之物；v.倒转 | |
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detention
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| n.滞留，停留；拘留，扣留；(教育)留下 | |
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actively
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| adv.积极地，勤奋地 | |
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binding
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| 有约束力的，有效的，应遵守的 | |
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hoops
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| n.箍( hoop的名词复数 )；（篮球）篮圈；（旧时儿童玩的）大环子；（两端埋在地里的）小铁弓 | |
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wrought
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| v.引起；以…原料制作；运转；adj.制造的 | |
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masonry
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| n.砖土建筑；砖石 | |
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preclude
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| vt.阻止，排除，防止；妨碍 | |
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adjourned
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| （使）休会， （使）休庭( adjourn的过去式和过去分词 ) | |
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possessed
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| adj.疯狂的；拥有的，占有的 | |
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tenacity
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| n.坚韧 | |
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corrosive
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| adj.腐蚀性的；有害的；恶毒的 | |
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alloy
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| n.合金，(金属的)成色 | |
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copper
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| n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的 | |
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brass
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| n.黄铜；黄铜器，铜管乐器 | |
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intervals
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| n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息 | |
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brittle
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| adj.易碎的；脆弱的；冷淡的；(声音)尖利的 | |
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worthy
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| adj.(of)值得的，配得上的；有价值的 | |
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fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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