ATMOSPHEEIC ELECTEICITY. 1 



By Prof. Arthur Schuster, F. R. S. 



It is hardly possible to imagine that the first experimenter who 

 obtained an electric spark sufficiently strong to produce a sensible 

 sound should not at once have been struck by the fact that he was in 

 the presence of thunder and lightning on a small scale. We find, 

 indeed, in various writings from the early days of electrical machines a 

 number of suggestions that the thunderstorm is an electrical phenom- 

 enon; but to Benjamin Franklin belongs the merit of having perceived 

 that a direct experiment was needed to prove what so far was only a 

 guess. In an article entitled "Opinions and conjectures concerning 

 the properties and effects of the electrical matter arising from experi- 

 ments and observations made at Philadelphia, 1749," the following 

 passage occurs : 



"To determine the question whether the clouds that contain light- 

 ning are electrified or not, I would propose an experiment to be tried 

 where it can be done conveniently. On the top of some high tower or 

 steeple place a kind of sentry-box, big enough to contain a man and 

 an electrical stand. From the middle of the stand let an iron rod rise 

 and pass, bending out of the door, and then upright 20 feet or 30 feet, 

 pointed very sharp at the end. If the electrical stand be kept clean 

 and dry, a man standing on it, when such clouds are passing low, 

 might be electrified and afford sparks, the rod drawing fire to him from 

 a cloud. 



"If any danger to the man should be apprehended (though I think 

 there would be none), let him stand on the floor of his box, and now 

 and then bring near to the rod the loop of a wire that has one end 

 fastened to the leads, he holding it by a wax handle, so the sparks, if 

 the rod is electrified, will strike from the rod to the wire and not affect 

 him." 2 



The experiment suggested by Franklin was successfully performed 

 in Marly (France), by DAlibard, on May 10, 1752, :! in London by Can- 

 ton, in Spital square, on July 20, 1752, and by Wilson, in Chelmsford, 



1 Discourse delivered before the Royal Institution of Great Britain, by Prof. 

 Arthur Schuster, F. R. S. Printed in Nature, No. 1366, Vol. LIII, January 2, 1896. 



2 "Experiments and observations on electricity made at Philadelphia, in America," 

 by Beujamin Franklin, LL. D. and F. R. S. (London, printed for David and Henry, 

 and sold by Francis Newbery, 1769, p. 66.) 



3 Ibid.,p.l07. 



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