电（选自《科学的故事书》法布尔）

这是一本关于科学的故事书，整本书用的是保罗叔叔给三个孩子讲故事的方式来讲科学，孩子们听够了虚构的故事，觉得真实的故事更引人入胜。很喜欢法布尔的故事，相比他那个年代，也许现在的小孩早早就知道什么是电，甚至电视、电脑……，但是别忘了爱因斯坦的话：“想象力比知识更重要。”让孩子拥有好奇心比记住简单的定理更重要。
第三十六章电   朱尔斯姐弟三个度过了漫长的一天。在这一天当中，每当有雷鸣电闪来临时，克莱尔就害怕得像片树叶瑟瑟发抖。“如果让我看到闪电劈到松树，”她说，“我一定会吓死的。”当孩子们平静下来后，他们都对雷电产生了好奇心，一致同意去找保罗叔叔，央求他给大伙儿讲讲雷电。于是第二天，朱尔斯、埃米尔和克莱尔就围在保罗叔叔身边，听他讲雷电的故事。朱尔斯先打开了话题。

“我现在已经不再害怕了，你能不能给我们讲讲，叔叔，为什么在暴风雨中，我们不能在大树下避雨呢？我敢肯定埃米尔一定想知道。”

“我最想知道的是雷到底是什么。”埃米尔说。

“我也想知道，”克莱尔说，“如果我们对雷有一点了解，就会更容易明白为什么在树下更危险了。”

“非常正确，”保罗叔叔赞成地说，“让我们先看看，你们哪个人能说说，对雷知道多少。”

“在我还很小的时候，”埃米尔自告奋勇地说，“我还以为天像个圆形的屋顶，雷是在天顶上，有一个大铁球在滚动发出的金属声。如果拱顶上有个地方漏了，球就掉下来，雷就会落到地面上了。但是现在我都这么大了，我可不相信这些了。”

“这么大了——一个还没长到我马甲第一颗纽扣高的小家伙！我想这不如说是你小小的理性思维能力在提高，让这种铁球的简单解释不能再令你信服了。”

克莱尔说：“我原来自己想过一些解释，也是不能让我信服。我想，雷是一辆重重的马车，上面拉着很多废铁。它在天顶上轰隆隆地行驶。有时候，轮子底下会产生火花，就像马蹄踏到石头那样：这就是闪电。天顶的边上是滑滑的，如果马车滑倒了，车上的废铁就掉到地上来，压伤人、树和房子。我昨天都对自己的解释感到好笑，但是我现在还是没有什么新想法：我对雷还是一无所知。”

“你们两个说的雷，都是你们不同形式的天真想象，都是来源于同样的理解，就是认为雷是天顶上的巨大声响。其实，蓝色的天顶只是环绕我们的空气，只不过因为它是厚厚的一层，才有了美丽的蓝色。在我们头上没有天顶，只有一层厚厚的大气；再往上什么也没有，一直到很远的距离，才能到达那些有星星的地方。”

“我们都放弃蓝色天顶的想法，”朱尔斯说，“埃米尔，克莱尔和我都被说服了，没有什么天顶。接着往下说吧。”

“接着说？接着这里开始说可有点难。我的孩子们，你们知不知道，你们的问题有时候很难回答？刚才说‘接着说’；充满了对你们保罗叔叔所拥有知识的信任，你们想要一个让人信服的答案，来满足你们的好奇心。但是，要知道，有数不清的东西超过了你们的智力，你们得到了比较明确的答案之后，不一定能够明白。随着年龄和知识的增长，现在对你们来说不懂的事情，将来会越来越清楚。产生雷的原因就是这样一个问题。我很乐意告诉你们关于雷的问题；但是如果你们不能全部理解我的话，这可能会挫伤你们小小的好奇心。对你们来说，这是个很难的问题，非常难。”

“你就告诉我们吧，”朱尔斯坚持说，“我们会聚精会神地听的。”

“那好吧。空气是看不见的，我们没法抓住它；如果它总是老老实实地呆在那里，可能你甚至会怀疑它是不是存在。但是当暴风吹弯了高大的杨树，把树叶吹散成涡旋，当它连根拔起树，吹走建筑的屋顶，谁会怀疑空气的存在呢？风就是空气从一个地方到另一个地方不停地流动。空气，我们看不见它，如此不易察觉，如此平静、沉寂，但却是真实存在的一种物质，在暴风的状态下甚至让人感到有点凶残。就是说，一个物质尽管有时候让人觉察不到，但它还是存在着。我们看不见摸不着它，感觉不到它，但是它还是存在，在我们周围；我们被它环绕着，我们生活在空气中。”

“然而，还是有东西藏在空气中，它更不可见，不易察觉。它无处不在，绝对是无处不在，甚至在我们自身当中；但是它自己保持得非常平静，直到现在，你们也听不到它的动静。”
埃米尔、克莱尔和朱尔斯交换了下充满疑惑的眼神，想要猜猜什么东西是无处不在但是他们又不知道的。保罗叔叔的这个谜让他们感到遥不可及。

“你们自己就是找上一整天、一整年、也许一辈子也找不出来，你们找不到它。我说的这样东西，藏得格外隐蔽；学者们不得不做精密的研究来认识它。让我们利用他们教给我们的方法，揭开谜底。”

保罗叔叔从他的桌子上拿来一根封口用的蜡，在他的衣袖上快速摩擦；把它靠近一个小纸片。孩子们都目不转睛地看着。他们惊讶地发现，纸片飞了起来粘到了封蜡上。实验重复了好几次。每次纸都会自己起来粘到蜡棒上。

“这小片蜡，开始不能吸纸，现在能了。在衣服上摩擦以后，产生了看不见的东西，因为蜡棒外面看不出有什么变化；这种看不见的东西却是真实存在的，因为它能把纸抬起来，拉到蜡上，粘在上面。这个东西叫做电。你们用一块玻璃棒或一片硫磺、松香或封蜡在衣服上摩擦都能很容易产生电。所有这些物质，当摩擦时，会获得一些吸引轻物的能力，比如一些稻草碎片，小纸片，灰尘。今天晚上，如果幸运的话，猫咪会告诉我们更多。”

The Story Book of Science图片占位：http://www.mainlesson.com/info/spacer.gif
by  Jean Henri Fabre

CHAPTER XXXVIELECTRICITY[155]

JULES gave a lengthy account of the day to his brother and sister. At the part relating to the thunderbolt Claire trembled like a leaf. "I should have died of fright," said she, "if I had seen the lightning strike the pine." After the deeper emotion came curiosity, and they all agreed to beg their uncle for a talk on the subject of thunder. And so the next day Jules, Emile, and Claire gathered around their Uncle Paul to hear him tell them all about it. Jules broached the subject.
"Now that I am no longer afraid, will you please tell us, Uncle, why we should not take refuge under trees during a storm? Emile, I am sure, would like to know."
"I should first of all like to know what thunder is," said Emile.
"I too," said Claire. "When we know a little what thunder is, it will be much easier to understand the danger from trees."
"Quite right," commented their uncle, approvingly. "First let us see whether any one of you knows anything about thunder."
"When I was very small," Emile volunteered, "I used to think it was produced by rolling a large ball of iron made of resounding metal over the vault of [156] the sky. If the vault broke anywhere, the ball was dashed to the ground and the thunder fell. But I don't believe that now. I am too big."
"Too big—a little fellow not so high as the first button on my vest! Say rather that your little reasoning powers are awakening and that the simple explanation of the iron ball no longer satisfies them."
Then Claire spoke. "I am not satisfied either with the explanations I used to give myself a while ago. With me, thunder was a wagon heavily loaded with old iron. It rolled on top of a sonorous vault. Sometimes a spark would flash out from under the wheels, the same as from a horse's hoof when it strikes a stone: that was the lightning. The vault was slippery and bordered with precipices. If the wagon happened to tip over, the load of old iron would fall to the ground, crushing people, trees, and houses. I laughed yesterday at my explanation, but I am no farther advanced now: I still know nothing at all about thunder."
"Your two thunders, varying to suit your infant imaginations, are based on the same idea, the idea of a sonorous vault. Well, know once for all that the blue vault of the sky is only an appearance due to the air which envelops us, and which, owing to the thickness of the envelope, has a beautiful blue color. Around us there is no vault, only a thick layer of air; and beyond that there is nothing for a vast distance until you come to the region of the stars."
"We will give up the blue vault," said Jules. "Emile, Claire, and I are persuaded there isn't any. Please go on."
[157] "Go on? Here is where difficulty begins. Do you know, my children, that your questions are sometimes very embarrassing? 'Go on' is soon said; and, filled with unbounded faith in your Uncle Paul's knowledge, you expect an answer which, you feel sure, will satisfy your curiosity. You must, however, understand that there are innumerable things beyond your intelligence, and before you can grasp them you must attain to riper reason. With age and study many things will become clear that now are dark to you. In this number is the cause of thunder. I am very willing to tell you something about it; but if you do not understand all that I say you must blame your own premature curiosity. It is a difficult subject for you, very difficult."
"Only tell us about it," Jules persisted; "we will listen attentively."
"So be it. Air is not visible, one cannot take hold of it; if it were always at rest you would not, perhaps, suspect its existence. But when a violent wind bends tall poplars and scatters the leaves in eddies, when it uproots trees and carries off the roofs of buildings, who can doubt the existence of air? For wind is only air streaming irresistibly from place to place. Air, so subtle, so invisible, so peaceful in repose, is therefore in very truth a material substance, even a very brutal one when in violent motion. That is to say, a substance can exist, although at times nothing betrays its presence. We do not see it or touch it, are not sensible of it, and yet it is there, all about us; we are surrounded by it, live in the midst of it.
[158] "Well, there is something still more hidden than air, more invisible, more difficult to detect. It is everywhere, absolutely everywhere, even in us; but it keeps itself so quiet that until now you have never heard of it."
Emile, Claire, and Jules exchanged glances full of meaning, trying to guess what it could be that was found everywhere and that they did not yet know of. They were a hundred leagues from guessing what their uncle meant.
"You might seek in vain by yourselves all day, all the year, perhaps all your life; you would not find it. The thing I am speaking of, you understand, is singularly well hidden; scholars had to make very delicate researches to learn anything about it. Let us make use of the means they have taught us to bring it to light."
Uncle Paul took from his desk a stick of sealing-wax and rubbed it rapidly over his cloth sleeve; then he put it near a small piece of paper. The children were all eyes. Behold, the paper flies up and sticks to the sealing-wax. The experiment is repeated several times. Each time the paper rises unaided, starts off, and fastens on to the stick.
"The piece of sealing-wax, which formerly did not attract the paper, now does. The rubbing on the cloth has, then, developed in it something that cannot be seen, for the stick has not changed in appearance; and this invisible thing is nevertheless very real, since it can lift up the paper, draw it to the wax, and hold it glued there. This thing is called electricity. You can easily produce it by rubbing on [159] cloth either a piece of glass or a stick of sulphur, resin, or sealing-wax. All these substances, when rubbed, will acquire the property of drawing to themselves very light objects, like small pieces of straw, little bits of paper, or particles of dust. This evening the cat shall teach us more about it, if it will be good."