ii6 Nichols: Franklin's 



more, for three or four generations of weak-minded 

 mortals is surely to be regarded as a benefactor! 



Franklin's theory of thunder storms, or as he termed it 

 in his fifth letter, written in 1749, his " new hypothesis 

 for explaining the several phenomena of thunder gusts " 

 was ingenious and altogether original. He regarded the 

 sea as the source of atmospheric electricity. " When," 

 he says, " there is a friction among the parts near its 

 surface the electrical fire is collected from the parts be- 

 low; it is then clearly visible in the night; it appears at 

 the stern and in the wake of every sailing vessel; every 

 dash of an oar shows it and every surf and spray. In 

 storms the whole sea seems on fire. The detached par- 

 ticles of water then repelled from the electrified surface 

 continually carry off the fire as it is collected; they rise 

 and form clouds and those clouds are highly electrified 

 and retain the fire until they have an opportunity of com- 

 municating it." 



Subsequently Franklin convinced himself by experi- 

 ments upon sea water that he was mistaken in supposing 

 the phosphorescence to be of electrical origin. He then 

 considered whether particles of air might not by their 

 friction against objects upon the surface of the earth be- 

 come electrified and impart their charge to the clouds 

 and he attempted to test this assumption by blowing a 

 stream of air by means of bellows against an insulated 

 conductor, but the experiment did not succeed. A later 



