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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

A Theory of Light and Heat

By Benjamin Franklin (1706–1790)

[Loose Thoughts on a Universal Fluid. 1784.]

UNIVERSAL space, as far as we know of it, seems to be filled with a subtile fluid, whose motion, or vibration, is called light….

In such case, as there may be a continuity or communication of this fluid through the air quite down to the earth, is it not by the vibrations given to it by the sun that light appears to us; and may it not be that every one of the infinitely small vibrations, striking common matter with a certain force, enters its substance, is held there by attraction, and augmented by succeeding vibrations, till the matter has received as much as their force can drive into it?

Is it not thus that the surface of this globe is continually heated by such repeated vibrations in the day, and cooled by the escape of the heat, when those vibrations are discontinued in the night, or intercepted and reflected by clouds?