FRANKLIN'S LEYDEN JAR EXPERIMENTS. 545 



amidst the smoke between the wire of the Leyden vial 

 and the snuffers. By the ai'd of the vial he u increases 

 the force of the electrical kiss vastly," and even the cork 

 ball, vibrating like the end of Guericke's thread, between 

 the Leyd'en jar and a conductor near by, is blackened and 

 given legs of linen thread, to make it into a counterfeit 

 spider which appears, to quote the genial philosopher once 

 more, " perfectly alive to persons unacquainted." The 

 words are almost identical with those which Porta, nearly 

 two centuries earlier, had used to describe the strange 

 behavior of the iron filings in the magnet field, and the 

 astonishment which their movements created among the 

 bystanders. 



Two months later, Franklin sends Collinson a second 

 letter, in which he describes the Leyden jar as electrified 

 positively within and negatively without, and marvels 

 that these two states of electricity the plus and minus 

 should be "combined and balanced in this miraculous 

 bottle ! situated and related to each other in a manner that 

 I can by no means comprehend!" He also connects his 

 plus and minus theory with the phenomena of attraction 

 and repulsion, by stating that "when a body is electrified 

 plus it will repel a positively electrified feather or small 

 cork ball. When minus (or when in the common state) it 

 will attract them, but stronger when minus than when in 

 the common state, the difference being greater." 



This is all hypothetical; yet it leads, through Franklin's 

 conviction that the equilibrium of the bottle is restored by 

 exterior communication between its inside and outside, to 

 a discovery of great moment, though he himself never 

 lived to realize its importance. 



Here is the experiment. A wire is fastened to the lead 

 coating of the jar and extends upwards so as to stand 

 parallel to the wire which enters the jar. A cork, sus- 

 pended on a silk thread, is placed between these wires, and 

 the jar is electrified and placed on wax. Then, says 

 Franklin, the cork "will play incessantly from one (wire) 

 35 



