A word, finally, about the messenger which brings to us all the knowledge we possess of the contents and marvels of space--light. Without the all-pervading luminiferous ether, narrow indeed would be our acquaintance with the physical creation. This is a sympathetic bond by which we may conceive that intelligent creatures throughout the universe are united. Light tells us of the existence of suns and systems so remote that the mind shrinks from the attempt to conceive their distance; and light bears back again to them a similar message in the feeble glimmering of our own sun. And can any one believe that there are no eyes out yonder to receive, and no intelligence to interpret that message? Sir Humphry Davy has beautifully expressed a similar thought in one of his philosophical romances: In Jupiter you would see creatures similar to those in Saturn, but with different powers of locomotion; in Mars and Venus you would find races of created forms more analogous to those belonging to the Earth; but in every part of the planetary system you would find one character peculiar to all intelligent natures, a sense of receiving impressions from light by various organs of vision, and toward this result you can not but perceive that all the arrangements and motions of the planetary bodies, their satellites and atmospheres, are subservient. The spiritual natures, therefore, that pass from system to system in progression toward power and knowledge preserve at least this one invariable character, and their intellectual life may be said to depend more or less upon the influence of light.[G] [G] See "Consolations in Travel, or, the Last Days of a Philosopher"; Dialogue I. Light is a result, and an expression, of the energy of cosmical life. The universe lives while light exists. But when the throbbing energies of all the suns are exhausted, and space is filled with universal gloom, the light of intelligence must vanish too. One can not read the wonderful messages of light--one can not study the sun, the moon, and the stars in any manner--without perceiving that the physical universe is enormously greater than he had thought, and that the creation, of which the Earth is an infinitesimal part, is almost infinitely more magnificent in actual magnitude than the imaginary domain which men of old times pictured as the dwelling-place of the all-controlling gods; without feeling that he has risen to a higher plane, and that his intellectual life has taken a nobler aim and a broader scope. INDEX. Achernar, 94. Albireo ([beta] Cygni), 55. Alcor, 27. Alcyone, 102. Maedler's "Central Sun," 104. Aldebaran, 22, 89, 91, 94, 95, 98. Algenib ([alpha] Persei), 84, 85. Algol, the Demon-Star, 83. probable cause of variation of, 85. Al-Mamoun, the Caliph, observation of a temporary star, 35. Almaach ([gamma] Andromedae), 79, 82. Alphard, 16.