DISTANCE, SIZE, AND MASS. 3

The first, as the most obvious peculiarity of themoon, is that continually varying aspect which hasled men in all ages to select the lunar orb as theemblem of change. “ The inconstant moon, thatnightly changes in her circled orb,” must, in the firstplace, have appeared as a body capable of assumingreally different shapes; and it is far from unlikelythat this apparent evidence of power, associated withthe moon’s rapid change of place among the stars,may have led to the earliest forms of Sabasanism.Yet in very early times the true explanation of thepeculiarity must have been obtained. The Chaldaeanastronomer undoubtedly recognized the moon as anopaque orb, shining only because reflecting thesun’s light ; for otherwise we should be unable toexplain the care with which they studied the moon’smotions in connection with the recurrence of lunarand solar eclipses. Their famous cycle, the Saros(of which I shall have occasion to speak more parti-cularly farther on), shows that they must have paidvery close attention to the moon’s movements for along period before the Saros was determined, and fora much longer period before the cycle was madeknown to other astronomers of ancient times. More-over, as they recognized in the moon the occasion ofsolar eclipses, though they could see her waning asshe approached the sun’s place, and waxing from thefinest crescent of light after passing him, it is clearthat they must have understood that the lunar phasesindicated no actual change of shape. Nor can web 2