prior to the Introduction of the Potentials. 47 



drop.' In order to account for the attraction between 

 oppositely charged bodies, in one of which there is an excess of 

 electricity as compared with ordinary matter, and in the other 

 an excess of ordinary matter as compared with electricity, he 

 assumed that " though the particles of electrical matter do repel 

 each other, they are strongly attracted by all other matter " ; so 

 that " common matter is as a kind of spunge to the electrical 

 fluid." 



These repellent and attractive powers he assigned only to 

 the actual (vitreous) electric fluid; and when later on the 

 mutual repidsion of resinously electrified bodies became known 

 to him,* it caused him considerable perplexity.f As we shall see, 

 the difficulty was eventually removed by.Aepinus. 



In spite of his belief in the power of electricity to act at a 

 distance, Franklin did not abandon the doctrine of effluvia. 

 "The form of the electrical atmosphere," he says,} "is that of the 

 body it surrounds. This shape may be rendered visible in a still 

 air, by raising a smoke from dry rosin dropt into a hot tea- 

 spoon under the electrified body, which will be attracted, and 

 spread itself equally on all sides, covering and concealing the 

 body, And this form it takes, because it is attracted by all 

 parts of the surface of the body, though it cannot enter the 

 substance already replete. Without this attraction, it would 

 not remain round the body, but dissipate in the air." He 

 observed, however, that electrical effluvia do not seem to 

 affect, or be affected by, the air ; since it is possible to breathe 

 freely in the neighbourhood of electrified bodies ; and moreover 

 a current of dry air does not destroy electric attractions and 

 repulsions. 



Kegarding the suspected identity of electricity with the 

 matter of heat, as to which Nollet had taken the affirmative 

 position, Franklin expressed no opinion. " Common fire," he 



* He refers to it in his Paper read to the Royal Society, December 18, 1755. 

 t Cf. letters xxxvii and xxxviii, dated 1761 and 1762. 

 1 New Experiment* , 1750, 15. 

 Letter vii, 1751. 



