A HISTORY OF SCIENCE 



Franklin* s belief, even at that thime, that lightning is 

 electricity. Many eminent observers, such as Hauks- 

 bee, Wall, Gray, and Nollet, had noticed the resem- 

 blance between electric sparks and lightning, but none 

 of these had more than surmised that the two might 

 be identical. In 1746, the surgeon, John Freke, also 

 asserted his belief in this identity. Winkler, short- 

 ly after this time, expressed the same belief, and, 

 assuming that they were the same, declared that 

 " there is no proof that they are of different natures" ; 

 and still he did not prove that they were the same 

 nature. 



Franklin Invents the Lightning-rod 



Even before Franklin proved conclusively the nature 

 of lightning, his experiments in drawing off the elec- 

 tric charge with points led to some practical sugges- 

 tions which resulted in the invention of the lightning- 

 rod. In the letter of July, 1750, which he wrote on 

 the subject, he gave careful instructions as to the way 

 in which these rods might be constructed. In part 

 Franklin wrote : " May not the knowledge of 'this power 

 of points be of use to mankind in preserving houses, 

 churches, ships, etc., from the stroke of lightning by 

 directing us to fix on the highest parts of the edifices 

 upright rods of iron made sharp as a needle, and gilt 

 to prevent rusting, and from the foot of these rods a 

 wire down the outside of the building into the grounds, 

 or down round one of the shrouds of a ship and down 

 her side till it reaches the water? Would not these 

 pointed rods probably draw the electrical fire silently 

 out of a cloud before it came nigh enough to strike, 



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