Soundings from the Atlantic Author:Oliver Wendell Holmes Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: THE STEREOSCOPE AND THE STEREOGRAPH. DEMOCRITUS of Abdera, commonly known as the Laughing Philosopher, , probably because he did not consider the study of tr... more »uth 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 to these effluences. They areperpetually shed from the surfaces of solids, as bark is shed by trees. Cortex is, indeed, one of the names applied to them by Lucretius. 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 hi 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 oft0, 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 largo 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 ma...« less