546 THE INTELLECTUAL RISE IN ELECTRICITY. 



to the other 'till the bottle is no longer electrified; that is, 

 it fetches fire from the top to the bottom (inside to outside) 

 of the bottle 'till the equilibrium is restored." 1 



Never before has the electrical fire shown itself in the 

 circuit other than as a spark, a shock, an explosion, in- 

 stantaneous "with a violence and quickness inexpressible." 

 Now Franklin is effecting this restoration of equilibrium 

 slowly. He is breaking up the explosion, so to speak, into 

 a great many little successive explosions. A very small 

 amount of the fire passing from wire to ball is enough to 

 electrify the latter, so that the wire will repel it. It 

 swings over to the opposite wire, to which it delivers its 

 charge, and swings back again. And thus it may go on 

 vibrating to and fro, until it has ferried over all the fire 

 which disturbs the electrical equilibrium between the out- 

 side of the jar and the inside. With this experiment (com- 

 monly cited as illustrating "electrical convection ") begins 

 the evolution of the electric current; the forging of the liuk 

 between the Leyden jar and the voltaic cell. 



The state of political affairs in Philadelphia when this 

 second letter was written (September, 1747) had become 

 critical. Trouble had arisen, several years before, between 

 England and Spain, as to the right to gather salt at Tor- 

 tugas and cut logwood at Cam peachy. Volunteers had 

 been raised in Pennsylvania for an invasion of Cuba, but 

 the colony would not take any measures to put itself in a 

 state of defense, even when war had broken out, not only 

 with Spain, but with France also. The Quakers of Phila- 

 delphia, in pursuance of their peculiar tenets, would 

 neither fight themselves, nor openly provide means for 

 others to fight. 2 On the day following that on which 

 Franklin's first letter to Collinson is dated, a French priva- 

 teer, anchored off Cape May, and her crew plundered houses 

 within twenty miles of Philadelphia. Still the Quakers 

 refused to provide any means of defense. Shortly after- 



1 See Fig. II. of Franklin's illustration on page 561. 

 2 McMaster: Benjamin Franklin as a man of Letters, N. Y., 1887. 



