Karl had thought of it, long before this time; and so had Caspar, just as long: for the kite had suggested it simultaneously1 to the minds of both.
It may be asked why they had not entertained the thought, and endeavoured to carry it into practical effect: since a balloon would have been far more likely to have delivered them out of their “mountain prison” than a paper kite?
But they had entertained the thought—at least, Karl had done so—and examined it in all its bearings. Caspar had permitted it to pass out of his mind, under the impression that they could not make a balloon; and Karl had arrived at the same conclusion; but only from a belief that they had not the materials with which to make one. Given the materials, Karl felt quite equal to the construction of a balloon—a rude one, it is true; but one which might have served the purpose for which they required it.
During the days when they had been occupied in making the paper-bird, he had given his thoughts a good deal to this subject; for, to say the truth, he had never been very sanguine2 about the success of the kite experiment. He had pondered long and patiently on the subject of balloons—endeavouring to recall to mind what little he had studied of aerostatics—and had mentally examined all the material objects within reach, in the hope of discovering some substance out of which one might be constructed.
Unfortunately, he had not been able to think of anything that appeared to be suitable. The daphne paper—even had it been in abundance—would not do: for paper of itself, however close in texture3, is not strong enough to withstand the pressure of the outside air—that is, in a balloon of sufficient size to carry any considerable weight. But it was of no use to talk of paper: since there was not enough; and Karl had given over thinking of a balloon: because there was nothing within reach likely to serve for its construction.
He knew that that great sphere would require to be air-proof. He had thought of the skins of animals; but such of these as might have been obtained in sufficient quantity, were entirely4 too thick and heavy to make the covering of a balloon. The hemp5, of which there was an abundance, might be woven into a cloth, and then coated over by gum obtained from some tree; for in the valley were several species of gum-exuding trees. But the question was, could they manufacture a cloth out of hemp that would be light enough when thus coated over? It was very doubtful whether they could—at all events they would have to practise the weaving trade for a long time, before they should arrive at a sufficient expertness to accomplish such a feat6. The plan was too unpromising to be seriously entertained; and Karl had dismissed it, along with the whole subject of the balloon.
That had been previous to the experiment of the kite, and its unfortunate ending. But now that all hope from this quarter had been brought to an end, the balloon once more began to shape itself in his mind, as well as in that of Caspar; and for the first time they proceeded to talk over the subject together.
“Cords we could have in plenty,” remarked Caspar, “but they’d be of no use, without the stuff to cover the great globe. They make it of silk, don’t they?”
“Yes,” replied Karl, “silk is the best material for the purpose.”
“And why?” inquired Caspar.
“Because it combines the three properties of lightness, strength, and closeness of texture, in a greater degree than any other known substance.”
“Would nothing else do?”
“Oh, yes; many things would answer to make a balloon, that might carry up a certain amount of weight. Even a paper balloon can be constructed to take up a few pounds—a cat, or a small dog; and people in many countries have been cruel enough to dispatch such creatures into the air, not caring what became of them.”
“Very cruel indeed!” assented7 Caspar, who, although a hunter, was far from having an unfeeling heart. “Such people should be sent up themselves in paper balloons.”
“Yes, if paper balloons would carry them; which, unfortunately for us, they wouldn’t. Even if we had an unlimited8 supply of paper, it would be of no use to us. We require something stronger, and more tenacious9.”
“Can we not think of something? Let us try, Karl!”
“Ah! dear brother, I have been trying for days, and in vain. There is nothing within this valley at all suitable for the purpose.”
“Would canvas do? Have you thought of that?”
“I have. It would be too coarse and heavy.”
“But, with great pains, could we not make it light enough? We might choose the finer fibres of the hemp; and spin and weave it with scrupulous10 care. Ossaroo here is a perfect Omphale in his way. I’ll warrant he could beat Hercules with the distaff.”
“Ho! brother!” exclaimed Karl, a little astonished. “You are quite classical in your speech this morning. Where learnt you the history of Hercules—you who have never seen the inside of a university?”
“You forget, brother Karl, that you yourself have been my instructor11 in these classical themes, as you call them. Though I must tell you that, with the exception of their occasionally lending a little ornament12 to my speech, I have derived13 not the slightest advantage from them; nor is it likely I ever shall.”
“Well, Caspar,” answered the botanist14, “I am not going to stand up for the classics, as you are well aware. Although I have taught you a little of their lore15, it was when I had nothing to do, and you were equally idle; otherwise I should have considered that both of us were wasting time. You already know my opinions on that subject—which are: that a knowledge of what is usually termed ‘the classics’ is of about as much use to a reasoning man as might be an equally profound knowledge of Chinese mnemonics16. The time I have spent in the study of the dead languages has been sheer waste; and all I have learnt wont17 raise us a foot higher here. My knowledge of Jupiter and Juno is not likely to gain us the means of getting out of our difficulty, no more than my acquaintance with Mercury will help me to a pair of wings. So a truce18 to classical ideas, and let us see whether scientific ones may not serve us better just now. You have a quick invention, brother Caspar; can you think of anything—I mean anything within our reach—that would make the air-bag of a balloon?”
“But could you make the balloon, if you had the stuff?” inquired Caspar, still in doubt whether any other than an experienced aeronaut could construct so wonderful a machine.
“Pooh!” replied the philosopher, “the making of a balloon is almost as easy as making a soap-bubble. Any air-tight bag, filled with heated atmosphere, becomes a balloon. The question is, what weight it can be made to carry—including the materials out of which it may be constructed.”
“But how are you to get the heated air into it?”
“Simply by making a fire under an aperture19 left open below.”
“But would not this air soon become cold again?”
“Yes; and then the balloon would sink back to the earth from the air inside getting cooled, and becoming as heavy as that without. Of course,” continued the philosopher, “you are aware that heated air is much lighter20 than the ordinary atmosphere; and that is why a balloon filled with the former, rises, and will continue rising, till it has reached that elevation21, where the rarefied atmosphere is as light as the heated air. Then it can go no further, and the weight of the balloon itself will bring it down again. A bladder of ordinary air sunk in water, or a corked22 bottle, will illustrate23 this point to your comprehension.”
“I comprehend it well enough,” rejoined Karl, rather piqued24 at being treated too much à l’enfant by his learned brother. “But I thought that, in a balloon, it was necessary to keep a fire constantly burning—a sort of grate or fire-basket suspended below. Now, even if we had the silk to make the great spherical25 bag, how could we make a fire-basket without iron?”
“We should not need the fire-basket you speak of. That is only required, when you design to keep your balloon some length of time in the air. If you only wish to make a short ascent26, once filling the bag with hot air is sufficient; as it would be for us here. Even if we wanted a suspended grate, surely, brother, you have enough ingenuity27 to get over such a trifling28 difficulty as that?”
“Well, I’m not so sure that I could. How would you get over it?”
“Why, by making a common basket, and lining29 it with clay. That would carry fire, as well as a vessel30 of either cast or wrought31 iron—at least sufficient to serve for a short excursion such as we should care to make. Now-a-days, fire is not used for inflating32 balloons. Inflammable gas has been found to be far superior for this purpose; but as we have no such thing in stock, we should have to proceed on the old original plan—that employed by the brothers Montgolfier—the first inventors of the balloon.”
“You think, then, that the fire apparatus33 could be dispensed34 with, if we could only discover some material that would make the great globe-shaped bag to contain the heated air?”
“Ay,” replied Karl; “think of something to do that, and I promise to make you a balloon.”
Thus challenged, Caspar set his wits to work; and for a long while he sat in silence, as if buried in some very profound speculation35. Probably, there was no material substance in that valley that did not pass in review before the retina of his mental vision; and all were considered in turn.
“It must be light, air-tight, and strong?” asked he, at length, as if there was something in his thoughts possessing these three requisites36.
“Light, air-tight, and strong,” answered Karl, simply repeating his words.
“The two last I am sure of,” rejoined Caspar. “Of the first only have I my doubts.”
“What is it?” asked Karl, in a tone that betrayed his interest in what Caspar had said.
“Eel-skins!” was the laconic37 answer.
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1
simultaneously
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| adv.同时发生地，同时进行地 | |
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sanguine
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| adj.充满希望的，乐观的，血红色的 | |
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texture
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| n.(织物)质地；(材料)构造；结构；肌理 | |
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entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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hemp
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| n.大麻；纤维 | |
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6
feat
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| n.功绩；武艺，技艺；adj.灵巧的，漂亮的，合适的 | |
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7
assented
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| 同意，赞成( assent的过去式和过去分词 ) | |
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8
unlimited
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| adj.无限的，不受控制的，无条件的 | |
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9
tenacious
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| adj.顽强的，固执的，记忆力强的，粘的 | |
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10
scrupulous
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| adj.审慎的，小心翼翼的，完全的，纯粹的 | |
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11
instructor
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| n.指导者，教员，教练 | |
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12
ornament
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| v.装饰，美化；n.装饰，装饰物 | |
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13
derived
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| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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14
botanist
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| n.植物学家 | |
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15
lore
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| n.传说；学问，经验，知识 | |
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16
mnemonics
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| n.记忆术 | |
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wont
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| adj.习惯于；v.习惯；n.习惯 | |
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18
truce
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| n.休战，(争执，烦恼等的)缓和；v.以停战结束 | |
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19
aperture
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| n.孔，隙，窄的缺口 | |
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20
lighter
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| n.打火机，点火器；驳船；v.用驳船运送；light的比较级 | |
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21
elevation
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| n.高度；海拔；高地；上升；提高 | |
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22
corked
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| adj.带木塞气味的，塞着瓶塞的v.用瓶塞塞住( cork的过去式 ) | |
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23
illustrate
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| v.举例说明，阐明；图解，加插图 | |
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piqued
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| v.伤害…的自尊心( pique的过去式和过去分词 )；激起（好奇心） | |
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spherical
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| adj.球形的；球面的 | |
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ascent
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| n.(声望或地位)提高；上升，升高；登高 | |
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ingenuity
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| n.别出心裁；善于发明创造 | |
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28
trifling
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| adj.微不足道的；没什么价值的 | |
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29
lining
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| n.衬里，衬料 | |
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30
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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31
wrought
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| v.引起；以…原料制作；运转；adj.制造的 | |
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32
inflating
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| v.使充气（于轮胎、气球等）( inflate的现在分词 )；（使）膨胀；（使）通货膨胀；物价上涨 | |
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33
apparatus
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| n.装置，器械；器具，设备 | |
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34
dispensed
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| v.分配( dispense的过去式和过去分词 )；施与；配（药） | |
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35
speculation
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| n.思索，沉思；猜测；投机 | |
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36
requisites
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| n.必要的事物( requisite的名词复数 ) | |
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37
laconic
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| adj.简洁的；精练的 | |
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