Stedman and Hutchinson, comps. A Library of American Literature: An Anthology in Eleven Volumes. 1891. Vol. III: Literature of the Revolutionary Period, 17651787
That Lightning Usually Passes from Earth to the Clouds
By Benjamin Franklin (17061790)
[Letter to Collinson, September, 1753.]
AT last, on the 12th of April, 1753, there being a smart gust of some continuance, I charged one phial pretty well with lightning, and the other equally, as near as I could judge, with electricity from my glass globe; and, having placed them properly, I beheld, with great surprise and pleasure, the cork ball play briskly between them, and was convinced that one bottle was electrized negatively.
I repeated this experiment several times during the gust, and in eight succeeding gusts, always with the same success; and being of opinion (for reasons I formerly gave in my letter to Mr. Kinnersley, since printed in London), that the glass globe electrizes positively, I concluded that the clouds are always electrized negatively, or have always in them less than their natural quantity of the electric fluid.
Yet, notwithstanding so many experiments, it seems I concluded too soon; for at last, June the 6th, in a gust which continued from five oclock, P.M., to seven, I met with one cloud that was electrized positively, though several that passed over my rod before, during the same gust, were in the negative state. This was thus discovered .
But this was a single experiment, which, however, destroys my first too general conclusion, and reduces me to this: That the clouds of a thunder-gust are most commonly in a negative state of electricity, but sometimes in a positive state.
The latter I believe is rare; for, though I, soon after the last experiment, set out on a journey to Boston, and was from home most part of the summer, which prevented my making farther trials and observations; yet Mr. Kinnersley, returning from the Islands just as I left home, pursued the experiments during my absence, and informs me that he always found the clouds in the negative state.