登陆注册
4714000000012

第12章

This inference appears inevitable, but his profound vision perceived its possible invalidity. He saw that it was at least possible that the difference of conducting power between the earth and the wire might give one an advantage over the other, and that thus a residual or differential current might be obtained. He combined wires of different materials, and caused them to act in opposition to each other, but found the combination ineffectual. The more copious flow in the better conductor was exactly counterbalanced by the resistance of the worse. Still, though experiment was thus emphatic, he would clear his mind of all discomfort by operating on the earth itself. He went to the round lake near Kensington Palace, and stretched 480 feet of copper wire, north and south, over the lake, causing plates soldered to the wire at its ends to dip into the water. The copper wire was severed at the middle, and the severed ends connected with a galvanometer. No effect whatever was observed.

But though quiescent water gave no effect, moving water might.

He therefore worked at London Bridge for three days during the ebb and flow of the tide, but without any satisfactory result. Still he urges, 'Theoretically it seems a necessary consequence, that where water is flowing there electric currents should be formed. If a line be imagined passing from Dover to Calais through the sea, and returning through the land, beneath the water, to Dover, it traces out a circuit of conducting matter one part of which, when the water moves up or down the channel, is cutting the magnetic curves of the earth, whilst the other is relatively at rest.... There is every reason to believe that currents do run in the general direction of the circuit described, either one way or the other, according as the passage of the waters is up or down the channel.' This was written before the submarine cable was thought of, and he once informed me that actual observation upon that cable had been found to be in accordance with his theoretic deduction.

Three years subsequent to the publication of these researches-- that is to say, on January 29, 1835--Faraday read before the Royal Society a paper 'On the influence by induction of an electric current upon itself.' A shock and spark of a peculiar character had been observed by a young man named William Jenkin, who must have been a youth of some scientific promise, but who, as Faraday once informed me, was dissuaded by his own father from having anything to do with science. The investigation of the fact noticed by Mr. Jenkin led Faraday to the discovery of the extra current, or the current induced in the primary wire itself at the moments of making and breaking contact, the phenomena of which he described and illustrated in the beautiful and exhaustive paper referred to.

Seven-and-thirty years have passed since the discovery of magneto-electricity; but, if we except the extra current, until quite recently nothing of moment was added to the subject. Faraday entertained the opinion that the discoverer of a great law or principle had a right to the 'spoils'--this was his term--arising from its illustration; and guided by the principle he had discovered, his wonderful mind, aided by his wonderful ten fingers, overran in a single autumn this vast domain, and hardly left behind him the shred of a fact to be gathered by his successors.

And here the question may arise in some minds, What is the use of it all? The answer is, that if man's intellectual nature thirsts for knowledge, then knowledge is useful because it satisfies this thirst. If you demand practical ends, you must, I think, expand your definition of the term practical, and make it include all that elevates and enlightens the intellect, as well as all that ministers to the bodily health and comfort of men. Still, if needed, an answer of another kind might be given to the question 'What is its use?'

As far as electricity has been applied for medical purposes, it has been almost exclusively Faraday's electricity. You have noticed those lines of wire which cross the streets of London. It is Faraday's currents that speed from place to place through these wires. Approaching the point of Dungeness, the mariner sees an unusually brilliant light, and from the noble phares of La Heve the same light flashes across the sea. These are Faraday's sparks exalted by suitable machinery to sunlike splendour. At the present moment the Board of Trade and the Brethren of the Trinity House, as well as the Commissioners of Northern Lights, are contemplating the introduction of the Magneto-electric Light at numerous points upon our coasts; and future generations will be able to refer to those guiding stars in answer to the question. What has been the practical use of the labours of Faraday? But I would again emphatically say, that his work needs no such justification, and that if he had allowed his vision to be disturbed by considerations regarding the practical use of his discoveries, those discoveries would never have been made by him. 'I have rather,' he writes in 1831, 'been desirous of discovering new facts and new relations dependent on magneto-electric induction, than of exalting the force of those already obtained; being assured that the latter would find their full development hereafter.'

In 1817, when lecturing before a private society in London on the element chlorine, Faraday thus expressed himself with reference to this question of utility. 'Before leaving this subject, I will point out the history of this substance, as an answer to those who are in the habit of saying to every new fact. "What is its use?"

Dr. Franklin says to such, "What is the use of an infant?" The answer of the experimentalist is, "Endeavour to make it useful." When Scheele discovered this substance, it appeared to have no use; it was in its infancy and useless state, but having grown up to maturity, witness its powers, and see what endeavours to make it useful have done.'

同类推荐
  • 释氏要览

    释氏要览

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 别传心法议

    别传心法议

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 清秘藏

    清秘藏

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 佛说坏相金刚陀罗尼经

    佛说坏相金刚陀罗尼经

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 太上老君戒经

    太上老君戒经

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
热门推荐
  • 情深几许,我的后半生

    情深几许,我的后半生

    那夜回家,是给我的母亲奔丧,昔日好闺蜜竟是插足父母婚姻的第三者!母亲是被父亲和我的好闺蜜联手算计而死。那一夜,我失去了亲情、友情。父亲和她觊觎母亲留给我的遗产,两人联手要将我送进监牢。我被伤得撕心裂肺,鲜血淋漓。直到他的出现,将我带离深渊。他像是一个神,永远能带领我走向希望的征途。我的前半生多是苦涩,往后有他,情深几许,我的后半生。--情节虚构,请勿模仿
  • 案生情愫

    案生情愫

    为了父亲的遗志而女承父业开始了自己刑警生涯的时候,白雪并不认为自己是有什么困难不能克服的,直到她遇到了肖戈言。这个光凭一张脸和身材就可以横扫娱乐圈的妖孽,偏偏要用头脑来吃饭,凭借乖张性格,一举成为犯罪学领域内最神(傲)秘(娇)的奇才。不怕复杂重口,就怕平淡无奇,再大的悬案在肖戈言面前都注定无法成为难题。而肖戈言却是白雪最大的难题。想知道怎么才能尴尬而不失礼貌的表达自己对这块“狗皮膏药”的嫌弃并且不被他的迷妹们活活打死?在线等,挺急的!
  • 任正非商业的逻辑

    任正非商业的逻辑

    《任正非商业的逻辑》向读者讲述华为从一个2万元起步、没有任何创新能力的微小企业成长为拥有14万多名员工、在150个国家设有分公司、代表处或研究所,年销售收入超过350亿美元的跨国公司,这种狂奔式发展背后的商业逻辑。《任正非商业的逻辑》作者经过长期观察和查找大量华为内部资料,全面梳理了华为创立30多年来的商业操作和重要讲话,深透地总结任正非的用人策略、营销秘诀、企业转型方法、未来战略规划,每一个要点都弥足珍贵。书中所论对企业高层领导、白领以及创业者有很大的启发作用。
  • 王妃是大厨

    王妃是大厨

    此文已加入五折特价书计划,全文看完不到三块钱哦!梧桐开新文啰,《太后要“出”墙》两小无猜却因差阳错成为第三者,心有不甘越过时空奔君而来虽是明媒正娶的王妃,却受尽冷落凭借高超厨艺拴住他的胃,得到他的心才发现,天意弄人,情敌竟然是故人进退两难爱情注定要有所伤害吗一定要有人牺牲吗不如归去,不如归去,决绝转身问苍天:哪一世才能修得正果爱情并没有先来后到,爱与不爱岂是用嘴说了就算善意的退让使爱成为双刃剑,受伤的岂只有她第一卷宿命预告“你不想娶我不想嫁,现在就给我休书吧,咱们两清。”新婚第三天,她就罢工。“早知道会这样,你干嘛非要嫁给我啊!害人害已。”他恼怒,任由小妾欺负她。以为一切都在掌控之中,却在接触中慢慢脱离了轨道时,她又说:原来都是故人。。。。。。你要好好待她,千万不要负了她啊。。。。。。于是狠心纳妾,却引狼入室,终成大错!悔不当初,却已没了她的影子第二卷美丽的南国预告本想逃离一切牵绊后,从此青灯古佛相伴,不想却成了战争的俘虏抚额哀叹:我怎么这么命苦啊!想不命苦?那要看你的表现啰!他邪邪地笑着,眼前这个小女人可比那个和亲公主有趣多了作为南国未来的皇帝,这是他该有的表现吗?刘嫣苦恼地看着他,他看起来比芮琨难对付多了或许还是留在沄国比较好!只是此生,大概没机会回去了“你必须嫁给他!如果不嫁,那就只好一辈子做的御用厨娘了!”“对不起,我不能……”刘嫣凄凉而又坚决。芮琨在她的身后重重地倒下,唇角轻扬,血迹洒在芳草地上,如同盛开的红花黎成看着视死如归的她,有一刹那的恍惚,喃喃道:“怪不得他对你如此倾心……”桐初次尝试,请大家多多支持啊,桐在此谢谢大家了!推荐全新现代总裁文《冷酷总裁契约妻》
  • 鲁滨逊漂流记(青少版名著)

    鲁滨逊漂流记(青少版名著)

    丹尼尔·笛福的这本《鲁滨逊漂流记》是一部具有传奇色彩的回忆录式 冒险小说。小说问世之后,立即风靡全球,历久不衰,成为家喻户晓的一部世界名著,该书被誉为英国文学史上的第一部长篇小说。 《鲁滨逊漂流记》运用自述的方式,讲述了主人公在孤岛上生活二十八年的传奇故事:鲁滨逊在绝境中流落无人荒岛之上,但是他凭借自己的勇敢 和智慧,对荒岛的原始生存环境进行改造,将自己的生活打理得井井有条,彻底改变了自己无衣无食的苦难命运,他还救下了即将被土著吃掉的野人“ 星期五”,并最终安全回到阔别已久的故乡。
  • 涌幢小品

    涌幢小品

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 御药院方

    御药院方

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 庄子翼

    庄子翼

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 小哲理大智慧:倒掉鞋里的沙

    小哲理大智慧:倒掉鞋里的沙

    在漫漫人生旅途,人们朝着成功和幸福的目标前进。每个人心中都有不落的太阳,我们会抬头看天,也会低头走路,难免会碰到障碍,难免会徘徊不前,速度缓慢,有时还会陷入误区。面对真实的人生,只有脚踏实地,逐步攀登,才能风光无限。使我们激动是奋斗与成功的喜悦,使我们心情悸动的还有诸多挫折、失败,而使我们懊恼沮丧的也许就源于那么一点点东西,一颗留在鞋里许久的颗粒。这个不被注意的角落让我们心力憔悴,错误连连。能倒掉鞋里的沙粒,就能攀登上人生的高峰。别为自己的挫折和错误流泪,最重要的是扫除心中的那粒沙。面对真实的社会和人生,只有付出一步一步攀登险峰的实践,才能贪略那无限的风光。
  • 中华营养百味:高血压调养食谱

    中华营养百味:高血压调养食谱

    为了满足高血压患者了解科学配餐,营养饮食的需要,通过寓医于食来预防疾病,减轻病痛,甚至帮助治愈疾病,《高血压调养食谱》针对高血压患者精选了具有食疗作用和营养功效的美味佳肴。使他们在家中就可以轻轻松松地做出既美味又有营养的饭菜来。让他们在品尝美味佳肴享受生活的同时,更收获到了营养、美丽和健康。