Observations and Suppositions Towards Forming a New Hypothesis for Explaining the Several Phenomena of Thunder Gusts
(1749)

Benjamin Franklin


Franklin, Papers, III:365

1. Non-Electrical Bodies, that have Electric Fire thrown into them, will retain it, 'till other Non-electrics, that have less, approach; and then 'tis communicated by a Snap, and becomes equally divided.
2. Electrical Fire loves Water, is strongly attracted by it, and they can subsist together.
3. Air is an Electric per se, and when dry, will not conduct the electrical Fire; it will neither receive it, nor give it to other bodies; otherwise, no Body surrounded by Air could be electrified positively and negatively: For should it be attempted positively, the Air would immediately take away the Overplus; or negatively, the Air would supply that what was wanting.
4. Water being electrified, the Vapours arising from it will be equally electrified; and floating in the air, in the form of Clouds or otherwise, will retain that quantity of electrical fire 'till they meet with other clouds or bodies not so much electrified; and will communicate as before mentioned...
9. The ocean is a compound of water a Non-Electric and salt an Electric per Se...
10. But clouds formed by vapours, raised from the sea, having both fires, and particularly a great quantity of the electrical, support their water strongly, raise it high; and, being moved by the winds, may bring it over the middle of the broadest continent, from the middle of the widest ocean...
32. If a country be plain, having no mountains to intercept the electrified clouds, yet it is not without means to make them deposite their water. For if an electrified cloud, coming from the sea meets in the air a cloud raised from the land and therefore not electrified; the first will flash its fire into the latter, and thereby both clouds shall be made suddenly to deposit water.
33. The electrified particles of the first cloud close when they lose their fire: the particles of the other cloud close in receiving it: in both they have thereby an opportunity of coalescing into drops. The concussion, or jerk, given to the air, distributes also to shake down the water; not only from those two clouds but from others near them. Hence the sudden fall of rain immediately after a flash of lightning...
39. As currents of air, with the clouds therein, pass different ways, 'tis easy to conceive how the clouds passing over each other, may attract with each other, and so come near enough for the electrical stroke; and also how electrical clouds may be carried within land very far from the sea before they have an opportunity to Strike...
41. When there is great heat on the land in a particular reason the Sun having shone on it perhaps several days while the surrounding countries have been screened by clouds, the lower air is rarefied and rises, the cooler denser air above descends; the clouds in that air meet from all sides, and joyn over the heated place; and if some are electrified, others not, lightning and thunder succeed and showers fall. Hence gusts after heats, and cooler air after gusts; the water and the clouds that bring it, coming from a higher and therefore a cooler region.
42. An electrical spark drawn from an irregular body at some distance is scarce ever straight, but shews crooked and wavering in the air; so do the flashes of lightning; the clouds being very irregular bodies.
43. As electrified clouds pass over a country, high hills and high trees, lofty towers, spires, masts of ships, chimneys, and &c. as so many prominences and points, draw the electrical fire, and the whole cloud discharges there.
44. Dangerous therefore, is it to shelter under a single tree during a thunder gust. It has been fatal to many, both men and beasts.

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