And just as in ruder lands each man looks at his own island, or village, as the center of the earth’s circle, so the ancients looked at the earth as the pivot of the universe, the central point around which all the heavenly hosts revolve. That was the fundamental principle of that Ptolemaic system which was older than Ptolemy; held in the most ancient times in Arabia, Babylon, Persia, and India, but first luminously expanded in the proportions and with the dignity of a system by Ptolemy. Its outlines were, in one word, this: there are seven planets, the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn; each has its own orbit, in which it is in a limited sense supreme, but they all revolve around the common center, the Earth. Beyond the seven, and including them all, is the Firmament, in which the other stars stand like golden nails in an imperishable floor; the whole vast external Firmament is opaque and motionless. The Ptolemaic system won and held the greatest regard in the ancient world. Mohammed established it in the Koran as a truth of religion. The advance of science revealed the falseness of the Ptolemaic scheme of the universe, and demonstrated the fact that the stars of heaven are not mere torch-bearers for us, and mere interpreters of human destinies, but are worlds like our own, our earth being but one of numberless thousands equally worthy of the Common Creator. The Copernican system, which was to re-create the whole domain of science, wrought this great change. The Sun, according to this theory, forms the central point around which, and not around the Earth, all the planets wheel. Copernicus, in 1543, left this imperfect and yet fruitful conception to his successors to unfold; and in the results gained by Kepler, in 1631, by Newton and Galileo, 1727, the Copernican system was firmly established. The vast improvements in the telescope removed the limits of the visible universe to a place till then unrevealed, and added inexhaustible fields to those which had been known before. The number of the planets was enlarged. The list of determined comets increases yearly. The number of the fixed stars has been determined by the extreme accuracy of such observers as Lalande, Lacaille, Bessel, Argelander, and Lamont. The great work of mapping and cataloguing the heavens has been accomplished. Many hundred stars, supposed to be single fixed stars, have been ascertained to be double stars, and some have been resolved into systems like our own. The 300-400, observed by Struve, have grown, through the labors of Herschel, in both the Northern and the Southern hemispheres, at the Cape of Good Hope, and elsewhere, to over 3000, and the number is constantly increasing. Nebulæ have been analyzed, and been shown to consist of worlds distinct and perfect as our own. Thus there is a steady and perceptible advance in man’s conception of the Earth, of Nature, of what we call the World and the Universe, though each individual, generation,