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Stedman and Hutchinson, comps. A Library of American Literature:
An Anthology in Eleven Volumes. 1891.
Vols. IX–XI: Literature of the Republic, Part IV., 1861–1889

That Lightning Usually Passes from Earth to the Clouds

By Benjamin Franklin (1706–1790)

[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 o’clock, 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.

So that, for the most part, in thunder-strokes, it is the earth that strikes into the clouds, and not the clouds that strike into the earth.