Page:Popular Science Monthly Volume 55.djvu/412

396

T is manifest that India is indebted for some of its astronomy to the Greeks. Not that it had not astronomy and astronomers from an epoch anterior to the invasion of Alexander. It had, in fact, been necessary to make observations of the heavens in order to fix a calendar that would enable the sacrifices of the Vedic ritual in connection with the return of the seasons and the revolutions of the stars to be celebrated at the right dates. Further, the belief in astrology, or the influence exercised by the movements of the planets on physical phenomena and all the events of human life, would lead, in India as elsewhere, to the observation and anticipation of everything relating to the conjunction and opposition of the heavenly bodies.

The Rig-Veda has allusions to the phases and stations of the moon. The stations (nakshatras) consisted, according to a tradition preserved by the Brahmans, of twenty-seven constellations (afterward twenty-eight) which the moon was supposed to traverse successively in the course of its sidereal revolution. A lunar zodiac and a primary division of time into months were thus obtained. The moon, moreover, bears in the Veda the name of month-maker (mâsakrit). Each station was assigned a uniform length of 13° 20' on the ecliptic, and a denomination, generally derived from mythology. The month, in turn, took its name from the constellation that had the honor of harboring the moon. Manon and the Djyotisha (a special treatise included among the Védângas, or commentaries on the Vedas) tell us that the year was composed of twelve months, the month of thirty days, the day of thirty hours, the hour of forty-eight minutes, all strictly sexagesimal subdivisions, like our own measures of time. The Djyotisha also teaches the art of constructing a clepsydra, or water-clock.

The adjustment of the solar year to correspond with the lunar year and of the two with the civil year dates from this period. The month was still composed of thirty days, but the solar years were grouped into quinquennial periods, in the middle and at the end of which the lunar month was doubled. Combining these quinquennial periods with the revolutions of the planet Brihaspati (Jupiter), which was calculated as occupying about twelve years, the Indian astronomers computed an astronomical cycle of sixty solar years. As the same cycle is found with the Chaldeans, where, according to Berosus, it was called the Sossos, we have to inquire how far Brahmanic astronomy was influenced by the systems which were