A HISTORY OF SCIENCE 



two bodies which are put near each other, to find out 

 the nature of their electricity, be rendered as electrical 

 as possible, for if one of them was not at all or but 

 weakly electrical, it would be attracted by the other, 

 though it be of that sort that should naturally be 

 repelled by it. But the experiment will always suc- 

 ceed perfectly well if both bodies are sufficiently 

 electrical." l 



As we now know, Dufay was wrong in supposing 

 that there were two different kinds of electricity, 

 vitreous and resinous. A little later the matter was 

 explained by calling one "positive " electricity and the 

 other " negative," and it was believed that certain sub- 

 stances produced only the one kind peculiar to that 

 particular substance. We shall see presently, how- 

 ever, that some twenty years later an English scien- 

 tist dispelled this illusion by producing both positive 

 (or vitreous) and negative (or resinous) electricity on 

 the same tube of glass at the same time. 



After the death of Dufay his work was continued 

 by his fellow-countryman Dr. Joseph Desaguliers, 

 who was the first experimenter to electrify running 

 water, and who was probably the first to suggest that 

 clouds might be electrified bodies. But about this 

 time that is, just before the middle of the eighteenth 

 century the field of greatest experimental activity 

 was transferred to Germany, although both England 

 and France were still active. The two German phi- 

 losophers who accomplished most at this time were 

 Christian August Hansen and George Matthias Bose, 

 both professors in Leipsic. Both seem to have con- 

 ceived the idea, simultaneously and independently, of 



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