

DUFAY'S EXPERIMENTS. 483 



body, itself insulated. Then the ball loses only a part of 

 its electricity, which goes to the last-named body. Conse- 

 quently he says, the volume of the electrified ball must be 

 considered. If too large, the virtue reaching it becomes / 

 too extended to act quickly; if not large enough, it will not 

 take all that is brought to it by the cord. These were the 

 first perceptions of the distribution of an electric charge on 

 a conductor. Gray had found it resident on the surface. 



Dufay now emulates the English philosopher in sus- 

 pending people by silk lines and electrifying them; but he 

 soon discards children and suspends himself. Then he 

 compares the sensation caused by an electrified tube near 

 his face to that of a spider-web drawn over it, and for the 

 first time feels the pricks and burns of the electric sparks 

 as they dart from his fingers. He believes them to be fire, 

 and, as such, altogether different from the hitherto seen 

 glow. 



His is a nimble mind, and it leaps from one subject to 

 another with marvelous rapidity. But this is necessary; 

 for he is not only breaking a new path, but rebuilding the 

 old one. As he meets a new problem he discovers that the 

 vantage ground from which he must proceed is infirm. 

 That necessitates re-examination of the foundation facts; 

 and in this way he finds himself side by side with Von 

 uericke, contemplating the singular behavior of the 

 feather which the sulphur globe drives away, and which, 

 levertheless, like the moon, always turns the same face, 

 ufay lets fall some gold-leaf upon his excited tube and 

 sees it repelled in the same way, avoiding the tube as he 

 :hases the fragments around the room. But if, mean- 

 diile, he rubs the tube, the leaf comes to it and goes 

 iway from it alternately, following the motion of the hand, 

 hen the leaf touches the tube, he says, it becomes elec- 

 "ified thereby by communication. Yet obviously it is re- 

 :lled. Therefore all electrified bodies first attract bodies / 

 :hat are not electrified, communicate to them their own 

 electricity, and that done, repel them. Nor will the latter 



