When I come to speak of what modern astronomy has done in furnishing us with new means of sound philosophical speculation on the being, attributes, and methods of God, it will be seen whether Lord Macaulay is correct in the assertion that it has added nothing to the argument. At present I will briefly advert to what the "early Greeks," or any of the Greeks, knew of the structure of the solar system. We learn, from a work which dates from nearly the middle of the second century of the Christian era, what was the general conception of the solar system among the ancients, including the Greeks. This work is known as the "Almagest" of Ptolemy, and the name of the "Ptolemaic System" has been given to the theory which he describes. This theory was common to all the ancient astronomers, Ptolemy's statement of it being a compendium of what they believed. Its principal features are these: 1. The heavens are a vast sphere, in which the heavenly bodies are set, and around the pole of this sphere they revolve in a circle every day. 2. The earth is likewise a sphere, and is situated in the center of the celestial plane as a fixed point. The earth having no motion, and being in the center of all the motions of the other bodies, the diurnal revolutions of those bodies are in a uniform motion around it. 3. The sun, being one of the heavenly bodies making a revolution around the earth, was supposed to be placed outside of the position of Venus in the heavenly sphere. The order of the Ptolemaic system was thus: The moon was first, being nearest to the earth; then came Mercury and Venus, the sun being between Venus and Mars. Beyond Mars came Jupiter and Saturn. Plato's arrangement was in one respect different, his order being the moon, the sun, Mercury, Venus, Mars, Jupiter, and Saturn. But this ideal heavenly sphere, with the earth in the center of all the revolutions of the other bodies, and remaining quiescent--a theory which was common to all the ancient astronomers--was the result of observing the motions of the heavenly bodies as they appear to a spectator on the earth. Such a spectator would have this appearance of a celestial sphere presented to him wherever he might be; and, judging from the apparent motions of the heavenly bodies relative to his own position at the center, he would conclude that the earth is at that center, and that it remains at rest, supported on nothing. It required certain discoveries to explode this system of a celestial sphere. First came Copernicus, who, about the middle of the sixteenth century of our era, published his demonstrations, which convinced the world of two great propositions: 1. That the diurnal revolution of the heavens is nothing but an apparent motion, caused by the revolution of the earth on its own axis. 2. That the earth is but one of a group of planets, all of which revolve around the sun as a center. Next came Kepler, who, in the early part of the