HAUKSBEE'S ELECTRIC MACHINE. 461 



continually over the varied results, for it is difficult to tell 

 when the light comes from the high heating of these sub- 

 stances, due to friction, and when not. 



At last a novel idea strikes him. Why rub glass in a 

 glass vessel exhausted of air ? Why not rub the exhausted 

 glass vessel itself? At once he mounts a glass globe in a 



HAUKSBEE'S ELECTRIC MACHINE. 



=ort of lathe, sets it whirling, and holds his hand to the 

 surface. The results, in point of brilliancy, overtop those 

 of all predecessors. 



1 Reproduced in reduced fac simile from Hauksbee's " Physico-Mechan- 

 ical Experiments on various subjects containing An Account of several 

 Surprizing Phenomena touching Light and Electricity." London: 1709. 

 The wavy lines on the globe are evidently intended to represent the play 

 of light therein. 



