"A man can hardly lift up his eyes toward the heavens," says Seneca, "without wonder and veneration, to see so many millions of radiant lights, and to observe their courses and revolutions, even without any respect to the common good of the Universe." Who does not sympathize with the feelings of Dante as he rose from his visit to the lower regions, until, he says, "On our view the beautiful lights of heaven Dawned through a circular opening in the cave, Thence issuing, we again beheld the stars." As we watch the stars at night they seem so still and motionless that we can hardly realize that all the time they are rushing on with a velocity far far exceeding any that man has ever accomplished. Like the sands of the sea, the stars of heaven have ever been used as an appropriate symbol of number, and we know that there are some 75,000,000, many, no doubt, with planets of their own. But this is by no means all. The floor of heaven is not only "thick inlaid with patines of bright gold," but is studded also with extinct stars, once probably as brilliant as our own sun, but now dead and cold, as Helmholtz tells us our sun itself will be some seventeen millions of years hence. Then, again, there are the comets, which, though but few are visible to us at once, are even more numerous than the stars; there are the nebulae, and the countless minor bodies circulating in space, and occasionally visible as meteors. Nor is it only the number of the heavenly bodies which is so overwhelming; their magnitude and distances are almost more impressive. The ocean is so deep and broad as to be almost infinite, and indeed in so far as our imagination is the limit, so it may be. Yet what is the ocean compared to the sky? Our globe is little compared to the giant orbs of Jupiter and Saturn, which again sink into insignificance by the side of the sun. The sun itself is almost as nothing compared with the dimensions of the solar system. Sirius is calculated to be a thousand times as great as the Sun, and a million times as far away. The solar system itself travels in one region of space, sailing between worlds and worlds, and is surrounded by many other systems as great and complex as itself; and we know that even then we have not reached the limits of the Universe itself.