482 THE INTELLECTUAL RISE IN ELECTRICITY. 



gauzes and the virtue went through black or red with equal 

 facility. He had been misled by the dressing which the 

 makers had put in the ribbons to give them body: that was 

 all the color exerted no influence. 



Perhaps this left him in something of a questioning 

 attitude toward Gray's other conclusions, for he begins to 

 investigate long-distance transmission anew; and finally 

 reaches the conclusion that the substances which are most 

 difficult to electrify such as metals or wet objects best 

 convey the virtue; while on the other hand, those easiest 

 excited amber or silk can hardly be got to convey it at 

 all. He puts up a packthread line 1256 feet long, and wets 

 it ; and the electricity traverses it with the same freedom 

 with which it nowadays runs along wet telegraph poles, or 

 escapes from the wires which touch the dripping foliage. 

 For Gray's silk supports, he substitutes glass tubes and 

 masses of Spanish wax, and thus, for the first time, uses 

 solid insulators upon an electric line of communication. 

 The new principle destroyed the non-electric and the 

 electric as distinctive significations it made non-electrics 

 into u conductors," and electrics into u non-conductors." 



Gray had shown how one line may electrify another 

 placed near it. Dufay varies this by placing two short 

 lines, respectively six and eight feet in length, end to end 

 with an air-space intervening. W/hen the gap is a foot 

 wide he says that the attraction, despite the shortness of 

 the lines, is as weak as if the virtue had traversed the con- 

 tinuous length of 1256 feet. Nevertheless it seems to him 

 that the charge can escape from line to air, and therefore 

 he says, coining the word, the necessity is apparent that 

 the transmitting cord should be ''insulated." 



He has meanwhile remarked that if he touches the ball; 

 hanging at the end of his electrified line, it refuses to at- 

 tract; the electricity, he says, being dissipated through 

 him to the floor. But suppose he touches it with a small 



1 " Que la corde dont on se sert pour transmettre au loin l'electricit soit 

 isolte." 



