These evanescent films may be seen in one of their aspects in any clear, calm sheet of water, in a mirror, in the eye of an animal by one who looks at it in front, but better still by the consciousness behind the eye in the ordinary act of vision.  They must be packed like the 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 potentially 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 straightway both the mirror and the mirrored forget what manner of man he was.  These visible films or membranous exuviae 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talked about, have no real existence, separable from their illuminated source, and perish instantly when it is withdrawn.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 his face was shedding 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.

This is just what the Daguerreotype has done.  It has fixed the most fleeting of our illusions, that which the apostle and the philosopher and the poet have alike used as the type of instability and unreality.  The photograph has completed the triumph, by making a sheet of paper reflect images like a mirror and hold them as a picture.

This triumph of human ingenuity is the most audacious, remote, improbable, incredible,—­the one that would seem least likely to be regained, if all traces of it were lost, of all the discoveries man has made.  It has become such an everyday matter with us, that we forget its miraculous nature, as we forget that of the sun itself, to which we owe the creations of our new art.  Yet in all the prophecies of dreaming enthusiasts, in all the random guesses of the future conquests over matter, we do not remember any prediction of such an inconceivable wonder, as our neighbor round the corner, or the proprietor of the small house on wheels, standing on the village common, will furnish any of us for the most painfully slender remuneration.  No Century of Inventions includes this among its possibilities.  Nothing but the vision of a Laputan, who passed his days in extracting sunbeams out of cucumbers, could have reached