Former Experiments.--The Doctor's Five Receptacles.--The Gas Cylinder1.-- The Calorifere.--The System of Manoeuvring.--Success certain.
"The attempt has often been made, gentlemen," said the doctor, "to rise and descend2 at will, without losing ballast or gas from the balloon. A French aeronaut, M. Meunier, tried to accomplish this by compressing air in an inner receptacle. A Belgian, Dr. Van Hecke, by means of wings and paddles, obtained a vertical3 power that would have sufficed in most cases, but the practical results secured from these experiments have been insignificant4.
"I therefore resolved to go about the thing more directly; so, at the start, I dispensed5 with ballast altogether, excepting as a provision for cases of special emergency, such as the breakage of my apparatus6, or the necessity of ascending7 very suddenly, so as to avoid unforeseen obstacles.
"My means of ascent9 and descent consist simply in dilating10 or contracting the gas that is in the balloon by the application of different temperatures, and here is the method of obtaining that result.
"You saw me bring on board with the car several cases or receptacles, the use of which you may not have understood. They are five in number.
"The first contains about twenty-five gallons of water, to which I add a few drops of sulphuric acid, so as to augment11 its capacity as a conductor of electricity, and then I decompose12 it by means of a powerful Buntzen battery. Water, as you know, consists of two parts of hydrogen to one of oxygen gas.
"The latter, through the action of the battery, passes at its positive pole into the second receptacle. A third receptacle, placed above the second one, and of double its capacity, receives the hydrogen passing into it by the negative pole.
"Stopcocks, of which one has an orifice twice the size of the other, communicate between these receptacles and a fourth one, which is called the mixture reservoir, since in it the two gases obtained by the decomposition13 of the water do really commingle14. The capacity of this fourth tank is about forty-one cubic feet.
"On the upper part of this tank is a platinum15 tube provided with a stopcock.
"You will now readily understand, gentlemen, the apparatus that I have described to you is really a gas cylinder and blow-pipe for oxygen and hydrogen, the heat of which exceeds that of a forge fire.
"This much established, I proceed to the second part of my apparatus. From the lowest part of my balloon, which is hermetically closed, issue two tubes a little distance apart. The one starts among the upper layers of the hydrogen gas, the other amid the lower layers.
"These two pipes are provided at intervals16 with strong jointings of india-rubber, which enable them to move in harmony with the oscillations of the balloon.
"Both of them run down as far as the car, and lose themselves in an iron receptacle of cylindrical17 form, which is called the heat-tank. The latter is closed at its two ends by two strong plates of the same metal.
"The pipe running from the lower part of the balloon runs into this cylindrical receptacle through the lower plate; it penetrates18 the latter and then takes the form of a helicoidal or screw-shaped spiral, the rings of which, rising one over the other, occupy nearly the whole of the height of the tank. Before again issuing from it, this spiral runs into a small cone19 with a concave base, that is turned downward in the shape of a spherical20 cap.
"It is from the top of this cone that the second pipe issues, and it runs, as I have said, into the upper beds of the balloon.
"The spherical cap of the small cone is of platinum, so as not to melt by the action of the cylinder and blow-pipe, for the latter are placed upon the bottom of the iron tank in the midst of the helicoidal spiral, and the extremity21 of their flame will slightly touch the cap in question.
"You all know, gentlemen, what a calorifere, to heat apartments, is. You know how it acts. The air of the apartments is forced to pass through its pipes, and is then released with a heightened temperature. Well, what I have just described to you is nothing more nor less than a calorifere.
"In fact, what is it that takes place? The cylinder once lighted, the hydrogen in the spiral and in the concave cone becomes heated, and rapidly ascends22 through the pipe that leads to the upper part of the balloon. A vacuum is created below, and it attracts the gas in the lower parts; this becomes heated in its turn, and is continually replaced; thus, an extremely rapid current of gas is established in the pipes and in the spiral, which issues from the balloon and then returns to it, and is heated over again, incessantly23.
"Now, the cases increase 1/480 of their volume for each degree of heat applied24. If, then, I force the temperature 18 degrees, the hydrogen of the balloon will dilate25 18/480 or 1614 cubic feet, and will, therefore, displace 1614 more cubic feet of air, which will increase its ascensional power by 160 pounds. This is equivalent to throwing out that weight of ballast. If I augment the temperature by 180 degrees, the gas will dilate 180/480 and will displace 16,740 cubic feet more, and its ascensional force will be augmented26 by 1,600 pounds.
"Thus, you see, gentlemen, that I can easily effect very considerable changes of equilibrium27. The volume of the balloon has been calculated in such manner that, when half inflated28, it displaces a weight of air exactly equal to that of the envelope containing the hydrogen gas, and of the car occupied by the passengers, and all its apparatus and accessories. At this point of inflation, it is in exact equilibrium with the air, and neither mounts nor descends29.
"In order, then, to effect an ascent, I give the gas a temperature superior to the temperature of the surrounding air by means of my cylinder. By this excess of heat it obtains a larger distention, and inflates30 the balloon more. The latter, then, ascends in proportion as I heat the hydrogen.
"The descent, of course, is effected by lowering the heat of the cylinder, and letting the temperature abate31. The ascent would be, usually, more rapid than the descent; but that is a fortunate circumstance, since it is of no importance to me to descend rapidly, while, on the other hand, it is by a very rapid ascent that I avoid obstacles. The real danger lurks32 below, and not above.
"Besides, as I have said, I have a certain quantity of ballast, which will enable me to ascend8 more rapidly still, when necessary. My valve, at the top of the balloon, is nothing more nor less than a safety-valve. The balloon always retains the same quantity of hydrogen, and the variations of temperature that I produce in the midst of this shut-up gas are, of themselves, sufficient to provide for all these ascending and descending33 movements.
"Now, gentlemen, as a practical detail, let me add this:
"The combustion34 of the hydrogen and of the oxygen at the point of the cylinder produces solely35 the vapor36 or steam of water. I have, therefore, provided the lower part of the cylindrical iron box with a scape-pipe, with a valve operating by means of a pressure of two atmospheres; consequently, so soon as this amount of pressure is attained37, the steam escapes of itself.
"Here are the exact figures: 25 gallons of water, separated into its constituent38 elements, yield 200 pounds of oxygen and 25 pounds of hydrogen. This represents, at atmospheric39 tension, 1,800 cubic feet of the former and 3,780 cubic feet of the latter, or 5,670 cubic feet, in all, of the mixture. Hence, the stopcock of my cylinder, when fully40 open, expends41 27 cubic feet per hour, with a flame at least six times as strong as that of the large lamps used for lighting42 streets. On an average, then, and in order to keep myself at a very moderate elevation43, I should not burn more than nine cubic feet per hour, so that my twenty-five gallons of water represent six hundred and thirty-six hours of aerial navigation, or a little more than twenty-six days.
"Well, as I can descend when I please, to replenish44 my stock of water on the way, my trip might be indefinitely prolonged.
"Such, gentlemen, is my secret. It is simple, and, like most simple things, it cannot fail to succeed. The dilation45 and contraction46 of the gas in the balloon is my means of locomotion47, which calls for neither cumbersome48 wings, nor any other mechanical motor. A calorifere to produce the changes of temperature, and a cylinder to generate the heat, are neither inconvenient49 nor heavy. I think, therefore, that I have combined all the elements of success."
Dr. Ferguson here terminated his discourse50, and was most heartily51 applauded. There was not an objection to make to it; all had been foreseen and decided52.
"However," said the captain, "the thing may prove dangerous."
"What matters that," replied the doctor, "provided that it be practicable?"
前人的尝试——博士的五只箱子——氢氧燃气喷嘴——加热设备——操作方法——必定成功
“先生们，过去人们常常试图能让气球自由升降，而又无需消耗氧气和扔掉压载物。法国气球飞行爱好者莫尼埃先生曾想通过压缩气球内空气容量的方法达到这个目的。比利时人范·埃克博士想用翅翼和小桨叶来生产一种垂直的力使气球任意升降，然而大多数情况下，这种垂直力太小。他们用各种方法取得的实际效果都不足可取。
“因此，我决定索性更加直截了当地着手解决这个问题。首先，除非是在万不得已的时候，例如设备坏了，或为了避开出乎意料之外的障碍非得在瞬间升起不可，我根本就不打算采取利用压载物使气球升降的办法。
“我采用的升降办法仅仅是改变一下温度，使封闭在气球里的气体膨胀或收缩，由此即可达到目的。下面给你们谈谈我是如何做到这点的：
“你们已看见了，把吊篮搬上船的时候还运上好几个你们不知道做什么用的箱子。这些箱子共五个。
“第一个箱子盛了约25加仑水，我往水中滴几滴硫酸增加水的导电性，然后，我通过一个电力大的本生电池把水分解。因为，你们知道，水是由两个氢原子和一个氧原子组成的。
“氧在电池的作用下经由阳极进入第二只箱子。第三只箱子放在第二只箱子上边。它的体积比头两只箱子大一倍。这只箱子用来接收从阴极流入的氢。
“这两只箱子上分别有一个开关通向第四只箱。其中一个开关的孔径比另一个大一倍。第四只箱可以称作混合箱。事实上，由水中分离出的两种气体就是在这只箱子里混合。混合箱的体积约为41立方尺①。
①等于150立方米。——原注
“在箱子的上方有一个白金管。管子上装有一个开关。
“先生们，现在你们已经弄明白了。我给你们描述的这个设备简直就是一个氢氧火焰喷枪。它喷出的氢氧混合气体燃烧时，热度超过打铁炉里炉火的温度。
“这部分清楚了，我再来谈谈第二部分设备：
“我这只气球的底部是完全密封的。两根间隔很小的管子从那儿伸出来：一根通到气球中的上层氢气里，另一根通到下层氢气里。
“这两根管子每隔一段距离就有一个牢固的橡胶接头。这使得管子在气球摆动时不至于出问题。
“两根管子都一直伸到吊篮里，通进一个圆筒形状的燃烧箱中。这只箱子叫加热箱，箱子的两端由两块用相同金属做成的高强度圆盘封闭着。
“气球下部伸出的管子穿过加热箱下面的金属盘进到这个圆筒状箱子中。箱子中的这部分管子做成螺旋状蛇形管。它们一圈叠一圈地盘起来几乎塞满了箱子的整个空间。蛇形管从箱子里伸出前先通到一个小圆锥体中。圆锥体的底部呈凹状，象个球冠，凸面朝下。
“第二根管子正是通过这个圆锥体的底端伸出，就像我给你们说过的那样，通到气球的上层氢气中。
“小圆锥体的球冠是用白金做的，为的是不至于在高温下溶化，因为燃烧喷嘴就装在铁箱底上一螺旋状蛇形管的中间。喷出的火苗将略微舔着这个白金球冠。
“先生们，你们知道什么是室内取暖用的暖气设备，知道它是如何工作的：房间的空气被迫通过一些管子，经过加热后再放出来时，温度高多了。我刚才给你们描述的东西，老实说，只不过是一种暖气设备而已。
“实际上会出现什么事呢？一旦点着燃烧喷嘴，蛇形管和四状圆锥体中的氢气就被烧热；加热了的氢气迅速沿着管子上升进到气球上部的氢气层中；下面随即行成空隙；而这个空隙又吸进气球下层的氢气，它们被加热后又顺着管子上升；空隙不断地被氢气填满，加热后的氢气源源不断地上升；这样，氢气从气球里出来加热后又回到气球中，如此循环往复，不停地加热，气体形成了一股热气流沿着管道和蛇形管迅速流动。
“既然氢气的温度升高1度，体积就增加1/480，那么，如果我把温度增加18度①， 气球中的氢气的体积将膨胀8/480，就是说1674立方尺②。因此，它将排挤掉1674立方尺的空气， 升力将增加160斤，这就等于扔掉同等重量的压载物。如果我把温度提高180度③， 氢气就会膨胀180/480，它将排挤掉16740立方尺空气，升力将加大1600斤。
①这里指的是华氏温度， 等于摄氏10度。如果把气体加热摄氏1度，它就比小零度时的体积大1—273。——原注。
②约合62立方米。——原注
③等于100摄氏度。本文中作者使用的均为华氏温度。
“先生们，你们明白了吧，我的确可以轻而易举地打破气球的平衡。气球的体积就是用这种方法算出来的。气球里只要充一半氢气，它排出的空气重量就与氢气包囊的重量、载人及所有货物的吊篮的重量相等。把气充到这一步时，气球在空中完完全全保持平衡了，既不上升也不下降。
“如果想升高，我就用喷嘴把氢气加热，使它的温度高于周围的气温。通过这种加热的办法，可获得更大的压力，使气球充得更大。氢气膨胀得越大，气球便会升得越高。
“减少氢氧喷嘴的温度，让氢气冷却下来，气球自然就下降了。因此一般说来，上升比下降要快得多。不过这种情况是值得庆幸的。对快速下降我从没有兴趣。恰恰相反，急速上升倒能使我避开障碍。要知道，我的危险是在下面而不是在上面。
“再着，我给你们说过，我有一些压载物。如果必要的话，扔掉它们能使我升起得更快些。我在气球上部安的那个活门，只不过是个安全阀。气球里的氢气始终是一丝不少的。我只要在这封密的气体中制造些温度变化，足以使气球上升或下降了。
“先生们，现在，再补充一点实用细节：
“氢气和氧气在喷嘴头燃烧时会产生些水蒸汽。为此，我在铁圆筒箱子下部装配了一根排气管。管子上有个阀门。只要超过两个大气压力，阀门就打开排气。所以，水蒸汽一达到这种压力，气体就自动排出。
“最后，给你们提供一些非常精确的数字：
按照水的构成元素， 25加仑水分解后可以生成200斤氧和25斤氢。正常大气压下，这相当于1890立方尺氧和3780立方尺氢①，也就是说，总共有5670立方尺的混合气。
①即70立方米氧和140立方米氢。——原注
“所以，我这个氢氧燃气喷嘴的开关完全打开时，每小时耗气27立方尺①。火焰的温度至少比大的照明灯火焰的温度高6倍。 这样平均算来，如果把气球停在空中不太高的地方保持不变的话， 我每小时用气不会超过9立方尺。那么我带的这25加仑水就可以使我在空中飞行630小时，换句话说，就是26天稍多点。”
①1立方米。——原注
“再说，因为我能任意降落，能在途中补充储备水，所以，我爱旅行多久就能旅行多久。
“先生们，这就是我的秘密。它很简单，而且，简单得不能再简单了，所以，不可能不成功。使气球中的气体热胀冷缩，这就是我的方法。这方法既不需要累赘的翅翼，也不需要机械动力。一套按我的要求使温度产生变化的加热设备，一个加热用的氢氧燃气喷嘴，既方便又轻巧，因此，我认为我已经具备了成功的一切必要条件。”
弗格森博士就此结束了他的讲话，作战室里立即响起了由衷敬佩的掌声，没有任何人对他的话提出异议，因为，一切都考虑那么周密，解决得那么恰当。
“不过，”舰长说，“我总觉得这可能很危险。”
“只要是可行的，危险又算什么！”博士简单地答道。
收听单词发音 |
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cylinder
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| n.圆筒，柱(面)，汽缸 | |
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descend
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| vt./vi.传下来，下来，下降 | |
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vertical
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| adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置 | |
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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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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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apparatus
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| n.装置，器械；器具，设备 | |
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ascending
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| adj.上升的，向上的 | |
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ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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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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dilating
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| v.（使某物）扩大，膨胀，张大( dilate的现在分词 ) | |
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augment
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| vt.(使)增大，增加，增长，扩张 | |
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decompose
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| vi.分解；vt.（使）腐败，（使）腐烂 | |
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decomposition
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| n. 分解, 腐烂, 崩溃 | |
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commingle
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| v.混合 | |
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platinum
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| n.白金 | |
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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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cylindrical
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| adj.圆筒形的 | |
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penetrates
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| v.穿过( penetrate的第三人称单数 )；刺入；了解；渗透 | |
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cone
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| n.圆锥体，圆锥形东西，球果 | |
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spherical
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| adj.球形的；球面的 | |
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extremity
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| n.末端，尽头；尽力；终极；极度 | |
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ascends
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| v.上升，攀登( ascend的第三人称单数 ) | |
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incessantly
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| ad.不停地 | |
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applied
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| adj.应用的；v.应用，适用 | |
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dilate
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| vt.使膨胀，使扩大 | |
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Augmented
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| adj.增音的 动词augment的过去式和过去分词形式 | |
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equilibrium
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| n.平衡，均衡，相称，均势，平静 | |
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inflated
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| adj.（价格）飞涨的；（通货）膨胀的；言过其实的；充了气的v.使充气（于轮胎、气球等）( inflate的过去式和过去分词 )；（使）膨胀；（使）通货膨胀；物价上涨 | |
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descends
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| v.下来( descend的第三人称单数 )；下去；下降；下斜 | |
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inflates
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| v.使充气（于轮胎、气球等）( inflate的第三人称单数 )；（使）膨胀；（使）通货膨胀；物价上涨 | |
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abate
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| vi.(风势，疼痛等)减弱，减轻，减退 | |
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lurks
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| n.潜在，潜伏；（lurk的复数形式）vi.潜伏，埋伏（lurk的第三人称单数形式） | |
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descending
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| n. 下行 adj. 下降的 | |
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combustion
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| n.燃烧；氧化；骚动 | |
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solely
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| adv.仅仅，唯一地 | |
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vapor
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| n.蒸汽，雾气 | |
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attained
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| （通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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constituent
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| n.选民；成分，组分；adj.组成的，构成的 | |
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atmospheric
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| adj.大气的，空气的；大气层的；大气所引起的 | |
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40
fully
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| adv.完全地，全部地，彻底地；充分地 | |
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41
expends
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| v.花费( expend的第三人称单数 )；使用（钱等）做某事；用光；耗尽 | |
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42
lighting
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| n.照明，光线的明暗，舞台灯光 | |
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elevation
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| n.高度；海拔；高地；上升；提高 | |
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44
replenish
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| vt.补充；(把…)装满；(再)填满 | |
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dilation
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| n.膨胀，扩张，扩大 | |
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contraction
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| n.缩略词，缩写式，害病 | |
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locomotion
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| n.运动，移动 | |
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48
cumbersome
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| adj.笨重的，不便携带的 | |
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49
inconvenient
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| adj.不方便的，令人感到麻烦的 | |
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50
discourse
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| n.论文，演说；谈话；话语；vi.讲述，著述 | |
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heartily
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| adv.衷心地，诚恳地，十分，很 | |
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decided
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| adj.决定了的，坚决的；明显的，明确的 | |
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