Thin Film (2)
from Oliver Wendell Holmes, “The Stereoscope and the Stereograph” Atlantic Monthly (1859)
Democritus of Abdera, commonly known as the Laughing Philosopher, probably because he did not consider the study of truth inconsistent with a cheerful countenance, believed and taught that all bodies were continually throwing off certain images like themselves, which subtile emanations, striking on our bodily organs, gave rise to our sensations. Epicurus borrowed the idea from him, and incorporated it into the famous system, of which Lucretius has given us the most popular version. Those who are curious on the matter will find the poet’s description at the beginning of his fourth book. Forms, effigies, membranes, or films, are the nearest representatives of the terms applied these effluences. They are perpetually shed from the surfaces of solids, as bark as shed by trees. Cortex is, indeed, one of the names applied to them by Lucretius.
These evanescent films may be seen in one of the aspects of any clear, calm sheet of water, in a mirror, in the eye of an animal by one who looks at it from the front, but better still by the consciousness behind the eye in the ordinary act of vision. They must be packed like leaves of a closed book; for suppose a mirror to give an image of an object a mile off, it will give one at every point less than a mile, though this were subdivided into a million parts. Yet the images will not be the same; for the one taken a mile off will be very small, at half a mile as large again, at a hundred feet, fifty times as large, and so on, as long as the mirror can contain the image.
Under the action of light, then, a body makes its superficial aspect present at a distance, becoming appreciable as a shadow or as a picture. But remove the cause,—the body itself,—and the effect is removed. The man beholdeth himself in the glass and goeth his way, and straightaway both the mirror and the mirrored forget what manner of man he was. These visible films or membranous exuviæ of objects, which the old philosophers talked about, have no real existence, separable from their illuminated source, and perish instantly when it is withdrawn.
If a man had handed a metallic speculum to Democritus of Abdera, and told him to look at his face in it while his heart was beating thirty or forty times, promising that one of the films should stick there, so that neither he, nor it, nor anybody should forget what manner of man he was, the Laughing Philosopher would probably have vindicated his claim to his title by an explosion that would have astonished the speaker.