“The same conditions, without exception, prevail everywhere. The deeper one descends6 in the earth, the hotter one finds the temperature. In deep mines the heat is such that the most unobservant workman is struck by it and wonders if he is not near some immense furnace.”
“The interior of the earth is, then, really a stove?” queried7 Jules.
“Much more than a stove, as you will see. The name of artesian well is given to a cylindrical8 hole which by means of strong iron bars, fitted end to end, is made in the ground until some reservoir of subterranean9 water, fed by the infiltrations of neighboring streams or lakes, is reached. The water that comes up from far under ground as the result of such a boring reaches the surface at a temperature equal to that of those depths; and thus we learn about the distribution of heat in the bowels10 of the earth. One of the most remarkable11 of these wells is that of Grenelle, at Paris. It is 547 meters deep, and the water in it is constantly at 28 degrees, a temperature almost as high as that of the hottest summer days. The water of the artesian well of Mondorf, on the frontier of France and Luxemburg, comes from a far greater depth, 700 meters. Its temperature is 35 degrees. Artesian wells, of which there are at present a considerable number, illustrate12 the same principle as mines: for every thirty meters of depth the heat increases one degree.”
“Then by digging wells deep enough we should at last come to boiling water?”
“Certainly. The difficulty is to attain13 the desired depth. To reach the temperature of boiling water it would be necessary to bore about three quarters of a league, which is impossible. However, a number of natural springs are known which, as they come from the ground, possess a high temperature, sometimes reaching the boiling point. They are called thermal14 springs, which means hot springs. There prevails, then, at the depth from which they come, a heat sufficient to make them tepid15, or even boiling hot. The most remarkable hot springs of France are those of Chaudes-Aigues and Vic, in Cantal. They are almost boiling.”
“Do these springs make streams that are different from others?”
“Steaming streams, in which you can plunge16 an egg for a moment and take it out cooked.”
“Then there are no little fish or crabs,” said Emile.
“Certainly not, my dear. You understand that if there were any they would be cooked through and through.”
“That is true.”
“The little streams of boiling water in Auvergne are nothing in comparison with what are seen in Iceland, that large island situated17 at the extreme north of Europe and covered with snow the greater part of the year. It has numbers of springs throwing up hot water, called in that country geysers. The most powerful, or the Great Geyser, springs from a large basin situated on the top of a hill formed by the smooth white incrustations deposited by the foam18 of the water. The interior of this basin is funnel-shaped and terminates in tortuous19 conduits penetrating20 to unknown depths.
“Each eruption21 of this volcano of boiling water is announced by a trembling of the earth and dull noises like distant detonations22 of some subterranean artillery23. Every moment the detonations become stronger; the earth trembles, and, from the bottom of the crater24, the water rushes up in an impetuous torrent25 and fills the basin, where, for a few moments, we have what looks like a boiler26 heated by some invisible furnace. In the midst of a whirlpool of steam the water rises in a boiling flood. Suddenly the geyser musters27 all its force: there is a loud explosion, and a column of water six meters in diameter spouts28 upward to the height of sixty meters, and falls again in steaming showers after having expanded in the shape of an immense sheaf crowned with white vapor29. This formidable outburst lasts only a few moments. Soon the liquid sheaf sinks; the water in the basin retires, to be swallowed up in the depths of the crater, and is replaced by a column of steam, furious and roaring, which spouts upward with thunderous reverberations and, in its indomitable force, hurls30 aloft huge masses of rock that have fallen into the crater, or breaks them into tiny bits. The whole neighborhood is veiled in these dense31 eddies32 of steam. Finally calm is restored and the fury of the geyser abates33, but only to burst forth34 again later and repeat the same program.”
Giant Geyser, Yellowstone National Park
“That must be terrible and beautiful at the same time,” commented Emile. “No doubt you look at this furious fountain from a long distance, so as not to be struck on the back by boiling showers.”
“What you have just told us, Uncle,” said Jules, “shows plainly that there is great heat under ground.”
“In admitting, as all these observations justify35 us in doing, that the subterranean temperature increases with the depth one degree for every thirty meters, it is estimated that at three kilometers or three quarters of a league down, the temperature must be that of boiling water, that is to say 100 degrees. Five leagues down, the heat is that of red-hot iron; at twelve leagues it is sufficient to melt all known substances. At a greater depth the temperature, apparently36, is still higher. Accordingly we are to imagine the earth is formed of a globe of matter liquefied by fire and enveloped37 by a thin crust of solid material that is upborne by that central ocean of melted minerals.”
“You say,” said Claire, “a thin crust of solid material; and yet, according to the calculations you have just mentioned, the thickness of the solid material must be about twelve leagues. Under that would be the melted matter. It seems to me twelve leagues make a good thickness, and we have nothing to fear from the subterranean fire.”
“Twelve leagues are very little in relation to the earth’s dimensions. The distance from the surface of the earth to its center is 1600 leagues. Of this distance about twelve leagues belong to the thickness of the solid crust, all the rest to the molten globe. On a ball two meters in diameter the solid crust of the earth would be represented by a thickness of half a finger’s breadth. Let us make a more simple comparison, representing the earth by an egg. Well, the egg-shell is the solid crust of the globe; its liquid content is the central mass in fusion38.”
“And we are separated from the immense subterranean furnace only by that thin shell!” exclaimed Jules. “That is not at all reassuring39.”
“I agree, it is not without a certain emotion that one hears for the first time what science tells us of these intimate details of the earth’s structure; one cannot think without fear of those burning abysses that roll their waves of melted minerals a few leagues under our feet. How can a covering, relatively40 so light, resist the fluctuations41 of the central liquid mass? This fragile crust, this shell of the globe, will it not some time melt, become disjointed, crumble42, or at least move? The little it does move makes continents tremble and the ground crack open in frightful43 chasms44.”
“Ah!” interposed Claire, “that is the cause of earthquakes. The liquid that is inside is stirred, and the shell moves.”
“It seems to me,” Jules remarked, “that this shell, comparatively so thin, ought to tremble oftener.”
“Perhaps not a day passes without the solid crust of the earth experiencing some shock, sometimes at one point, sometimes at another, beneath the bed of the seas, as well as under the continents. However, disastrous45 earthquakes are very rare, thanks to the intervention46 of volcanoes.
“Volcanic47 orifices are, in fact, veritable safety-valves, which put the interior of the globe in communication with the exterior48. By offering permanent vents49 to the subterranean vapors50 that tend to liberate51 themselves by overturning the earth, they render earthquakes less frequent and less disastrous. In volcanic countries every time the ground is shaken by strong shocks, the earthquake ceases the moment the volcano begins to throw up its fumes52 and lava53.”
“I well remember,” said Jules, “your account of the eruption of Etna and the Catanian disaster. At first I only saw in volcanoes terrible mountains spreading devastation54 around them; now I begin to see their great use, their necessity. Without their air-holes, the earth would seldom be still.”
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1
excavation
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| n.挖掘，发掘；被挖掘之地 | |
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inaccessible
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| adj.达不到的，难接近的 | |
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landslides
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| 山崩( landslide的名词复数 )； （山坡、悬崖等的）崩塌； 滑坡； （竞选中）一方选票占压倒性多数 | |
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rigors
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| 严格( rigor的名词复数 )； 严酷； 严密； （由惊吓或中毒等导致的身体）僵直 | |
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5
stifled
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| （使）窒息， （使）窒闷( stifle的过去式和过去分词 )； 镇压，遏制； 堵 | |
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6
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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7
queried
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| v.质疑，对…表示疑问( query的过去式和过去分词 )；询问 | |
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cylindrical
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| adj.圆筒形的 | |
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subterranean
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| adj.地下的，地表下的 | |
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bowels
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| n.肠，内脏，内部；肠( bowel的名词复数 )；内部，最深处 | |
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remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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illustrate
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| v.举例说明，阐明；图解，加插图 | |
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attain
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| vt.达到，获得，完成 | |
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thermal
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| adj.热的，由热造成的；保暖的 | |
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tepid
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| adj.微温的，温热的，不太热心的 | |
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plunge
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| v.跳入，(使)投入，(使)陷入；猛冲 | |
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situated
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| adj.坐落在...的，处于某种境地的 | |
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foam
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| v./n.泡沫，起泡沫 | |
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tortuous
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| adj.弯弯曲曲的，蜿蜒的 | |
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penetrating
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| adj.（声音）响亮的，尖锐的adj.（气味）刺激的adj.（思想）敏锐的，有洞察力的 | |
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21
eruption
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| n.火山爆发；（战争等）爆发；（疾病等）发作 | |
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detonations
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| n.爆炸 （声）( detonation的名词复数 ) | |
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artillery
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| n.(军)火炮，大炮；炮兵(部队) | |
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crater
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| n.火山口，弹坑 | |
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torrent
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| n.激流，洪流；爆发，(话语等的)连发 | |
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boiler
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| n.锅炉；煮器(壶，锅等) | |
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musters
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| v.集合，召集，集结（尤指部队）( muster的第三人称单数 )；（自他人处）搜集某事物；聚集；激发 | |
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28
spouts
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| n.管口( spout的名词复数 )；（喷出的）水柱；（容器的）嘴；在困难中v.（指液体）喷出( spout的第三人称单数 )；滔滔不绝地讲；喋喋不休地说；喷水 | |
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vapor
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| n.蒸汽，雾气 | |
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hurls
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| v.猛投，用力掷( hurl的第三人称单数 )；大声叫骂 | |
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dense
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| a.密集的，稠密的，浓密的；密度大的 | |
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eddies
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| （水、烟等的）漩涡，涡流( eddy的名词复数 ) | |
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abates
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| 减少( abate的第三人称单数 )； 减去； 降价； 撤消（诉讼） | |
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forth
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| adv.向前；向外，往外 | |
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justify
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| vt.证明…正当(或有理)，为…辩护 | |
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apparently
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| adv.显然地；表面上，似乎 | |
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enveloped
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| v.包围，笼罩，包住( envelop的过去式和过去分词 ) | |
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38
fusion
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| n.溶化；熔解；熔化状态，熔和；熔接 | |
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reassuring
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| a.使人消除恐惧和疑虑的，使人放心的 | |
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relatively
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| adv.比较...地，相对地 | |
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41
fluctuations
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| 波动，涨落，起伏( fluctuation的名词复数 ) | |
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42
crumble
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| vi.碎裂，崩溃；vt.弄碎，摧毁 | |
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43
frightful
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| adj.可怕的；讨厌的 | |
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44
chasms
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| 裂缝( chasm的名词复数 )； 裂口； 分歧； 差别 | |
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45
disastrous
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| adj.灾难性的，造成灾害的；极坏的，很糟的 | |
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intervention
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| n.介入，干涉，干预 | |
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47
volcanic
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| adj.火山的；象火山的；由火山引起的 | |
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exterior
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| adj.外部的，外在的；表面的 | |
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49
vents
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| （气体、液体等进出的）孔、口( vent的名词复数 )； （鸟、鱼、爬行动物或小哺乳动物的）肛门； 大衣等的)衩口； 开衩 | |
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50
vapors
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| n.水汽，水蒸气，无实质之物( vapor的名词复数 )；自夸者；幻想 [药]吸入剂 [古]忧郁（症）v.自夸，（使）蒸发( vapor的第三人称单数 ) | |
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51
liberate
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| v.解放，使获得自由，释出，放出；vt.解放，使获自由 | |
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52
fumes
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| n.(强烈而刺激的)气味，气体 | |
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53
lava
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| n.熔岩，火山岩 | |
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54
devastation
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| n.毁坏；荒废；极度震惊或悲伤 | |
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