Humboldt, in his Cosmos, states that the Chinese had magnetic carriages with which to guide themselves across the great plains of Tartary, one thousand years before our era, on the principle of the compass. The Romans used movable types to mark their pottery and indorse their books. Layard found in Nineveh a magnifying lens of rock crystal, which Sir David Brewster considers a true optical lens, and the origin of the microscope. Experiments foreshadowing photography, giving remarkable results, began to be made more than three centuries ago, and more than two and a half centuries before Daguerre. The principle of the stereoscope, invented by Professor Wheatstone, was known to Euclid, described by Galen fifteen hundred years ago, and more fully long afterward in the works of Giambattista Porta. The Thames Tunnel, thought such a novelty, was anticipated by that under the Euphrates at Babylon. "It is usually attributed to Aristotle, indeed, as his peculiar glory," says an authority on mental philosophy, "that he should at once have originated, and brought to perfection, a science which, for more than two thousand years, has received few alterations, found few minds capable of suggesting improvements. Recent labors of Orientalists have, however, brought to light the fact that in India, long before the palmy days of Grecian philosophy, logic was pursued with vigor as a study and science. The Nyaya of Gotama holds, in the Indian systems of philosophy, much the same place the Organon of Aristotle holds with us. The two, however, are quite independent of each other. Aristotle was no disciple of Gotama."