298 Otto Guerlcke, Wall* ,- lee. [Book IV. 



riments. He ad.ied to the (lock of knowledge the 



O 



diioovery, th;i once attracted by an excited 



electric v, .d by it, and not attracted again till 



it had touched fome other body. Thus he was able 

 to keep a feather fuipended in the air over his globe 

 of fuiphur ; but he obferved, that if he drove i: near 

 a linen tiiread, or the flame of a candle, it inrhntly 

 recovered its propenfity (if I may ufe the exprefiion) 

 for approaching the globe again. The hiffin noife, 

 and the gleam of light which his globe afforded, both 

 attracted his notice. 



Thefe circumftances were, however, afterwards ac- 

 'curately remarked by Dr. 'Wall, who, by rubbing am- 

 ber upon a woollen fubiiance in the dark, found alfo 

 that light was produced in considerable quantities, ac- 

 companied with a crackling noife; and what is ftill 

 more extraordinary, he adds, " this light and crack- 

 ling feems, in fome degree, to reprdent thunder and 

 lightning." 



Mr. Hawkfbee firft obferved the great electric 

 power of glafs. He conftructed a wooden machine, 

 which enabled him conveniently to put a glafs globe 

 in motion. He confirmed all the experiments of Dr. 

 Wall. He obferved, that the light emitted by the 

 friction of electric bodies, befides the crackling noife, 

 was accompanied by an acute fenfe of feeling when 

 applied to his hand. He fays, that, all the powers of 

 electricity were improved by warmth, and diminifhed 

 by moifture. 



Hitherto the diftinction between thofe bodies which 

 are capable of being excited to electricity and thofe 

 which are only capable of receiving it from the others, 

 appears fcarcely to have been fufpected. About the 

 year 1729, this great difcovery was made by Mr. 

 Grey, a penfioner of the Charter- Houfe. After fome 



fruitlefc 



