a history of science-2-第54章
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himself was aflame with excitement； and so determined in his efforts to produce still stronger electric currents； that he sacrificed the tube of his twenty…foot telescope for the construction of a mammoth electrical machine。 With this great machine a discharge of electricity was generated powerful enough to wound the skin when it happened to strike it。 Until this time electricity had been little more than a plaything of the scientistsor； at least； no practical use had been made of it。 As it was a practising physician； Gilbert； who first laid the foundation for experimenting with the new substance； so again it was a medical man who first attempted to put it to practical use； and that in the field of his profession。 Gottlieb Kruger； a professor of medicine at Halle in 1743； suggested that electricity might be of use in some branches of medicine； and the year following Christian Gottlieb Kratzenstein made a first experiment to determine the effects of electricity upon the body。 He found that 〃the action of the heart was accelerated； the circulation increased； and that muscles were made to contract by the discharge〃： and he began at once administering electricity in the treatment of certain diseases。 He found that it acted beneficially in rheumatic affections； and that it was particularly useful in certain nervous diseases； such as palsies。 This was over a century ago； and to…day about the most important use made of the particular kind of electricity with which he experimented （the static； or frictional） is for the treatment of diseases affecting the nervous system。 By the middle of the century a perfect mania for making electrical machines had spread over Europe； and the whirling； hand…rubbed globes were gradually replaced by great cylinders rubbed by woollen cloths or pads； and generating an 〃enormous power of electricity。〃 These cylinders were run by belts and foot…treadles； and gave a more powerful； constant； and satisfactory current than known heretofore。 While making experiments with one of these machines； Johann Heinrichs Winkler attempted to measure the speed at which electricity travels。 To do this he extended a cord suspended on silk threads； with the end attached to the machine and the end which was to attract the bits of gold…leaf near enough together so that the operator could watch and measure the interval of time that elapsed between the starting of the current along the cord and its attracting the gold…leaf。 The length of the cord used in this experiment was only a little over a hundred feet； and this was； of course； entirely inadequate； the current travelling that space apparently instantaneously。 The improved method of generating electricity that had come into general use made several of the scientists again turn their attention more particularly to attempt putting it to some practical account。 They were stimulated to these efforts by the constant reproaches that were beginning to be heard on all sides that electricity was merely a 〃philosopher's plaything。〃 One of the first to succeed in inventing something that approached a practical mechanical contrivance was Andrew Gordon； a Scotch Benedictine monk。 He invented an electric bell which would ring automatically； and a little 〃motor；〃 if it may be so called。 And while neither of these inventions were of any practical importance in themselves； they were attempts in the right direction； and were the first ancestors of modern electric bells and motors； although the principle upon which they worked was entirely different from modern electrical machines。 The motor was simply a wheel with several protruding metal points around its rim。 These points were arranged to receive an electrical discharge from a frictional machine； the discharge causing the wheel to rotate。 There was very little force given to this rotation； however； not enough； in fact； to make it possible to more than barely turn the wheel itself。 Two more great discoveries； galvanism and electro…magnetic induction； were necessary before the practical motor became possible。 The sober Gordon had a taste for the spectacular almost equal to that of Bose。 It was he who ignited a bowl of alcohol by turning a stream of electrified water upon it； thus presenting the seeming paradox of fire produced by a stream of water。 Gordon also demonstrated the power of the electrical discharge by killing small birds and animals at a distance of two hundred ells； the electricity being conveyed that distance through small wires。
THE LEYDEN JAR DISCOVERED As yet no one had discovered that electricity could be stored； or generated in any way other than by some friction device。 But very soon two experimenters； Dean von Kleist； of Camin； Pomerania； and Pieter van Musschenbroek； the famous teacher of Leyden； apparently independently； made the discovery of what has been known ever since as the Leyden jar。 And although Musschenbroek is sometimes credited with being the discoverer； there can be no doubt that Von Kleist's discovery antedated his by a few months at least。 Von Kleist found that by a device made of a narrow…necked bottle containing alcohol or mercury； into which an iron nail was inserted； be was able to retain the charge of electricity； after electrifying this apparatus with the frictional machine。 He made also a similar device； more closely resembling the modern Leyden jar； from a thermometer tube partly filled with water and a wire tipped with a ball of lead。 With these devices he found that he could retain the charge of electricity for several hours； and could produce the usual electrical manifestations； even to igniting spirits； quite as well as with the frictional machine。 These experiments were first made in October； 1745； and after a month of further experimenting； Von Kleist sent the following account of them to several of the leading scientists； among others； Dr。 Lieberkuhn； in Berlin； and Dr。 Kruger； of Halle。 〃When a nail； or a piece of thick brass wire； is put into a small apothecary's phial and electrified； remarkable effects follow； but the phial must be very dry； or warm。 I commonly rub it over beforehand with a finger on which I put some pounded chalk。 If a little mercury or a few drops of spirit of wine be put into it； the experiment succeeds better。 As soon as this phial and nail are removed from the electrifying…glass； or the prime conductor； to which it has been exposed； is taken away； it throws out a pencil of flame so long that； with this burning machine in my hand； I have taken above sixty steps in walking about my room。 When it is electrified strongly； I can take it into another room and there fire spirits of wine with it。 If while it is electrifying I put my finger； or a piece of gold which I hold in my hand； to the nail； I receive a shock which stuns my arms and shoulders。 〃A tin tube； or a man； placed upon electrics； is electrified much stronger by this means than in the common way。 When I present this phial and nail to a tin tube； which I have； fifteen feet long； nothing but experience can make a person believe how strongly it is electrified。 I am persuaded；〃 he adds； 〃that in this manner Mr。 Bose would not have taken a second electrical kiss。 Two thin glasses have been broken by the shock of it。 It appears to me very extraordinary； that when this phial and nail are in contact with either conducting or non…conducting matter； the strong shock does not follow。 I have cemented it to wood； metal； glass； sealing…wax； etc。； when I have electrified without any great effect。 The human body； therefore； must contribute something to it。 This opinion is confirmed by my observing that unless I hold the phial in my hand I cannot fire spirits of wine with it。〃＇2＇ But it seems that none of the men who saw this account were able to repeat the experiment and produce the effects claimed by Von Kleist； and probably for this reason the discovery of the obscure Pomeranian was for a time lost sight of。 Musschenbroek's discovery was made within a short time after Von Kleist'sin fact； only a matter of about two months later。 But the difference in the reputations of the two discoverers insured a very different reception for their discoveries。 Musschenbroek was one of the foremost teachers of Europe； and so widely known that th
