Page:Popular Science Monthly Volume 27.djvu/563

Rh a Chinese date with the corresponding date of any other chronology, were it not that the learned from the most ancient times have used a cycle of sixty days in much the same manner as we use our week of seven days, without regard to the movements of the sun and the moon. This calendar has become of prime necessity for fixing the year in which a particular day may have fallen; and the preparation of it is considered a matter of such importance that it is confided to an imperial mathematical tribunal, and, when the work is completed, it is ceremoniously presented to the members of the imperial family and the chief personages of the government.

The Chinese years are designated by two numbers. The first, the official number, indicates the number of the years of the reign of the emperor, and is variable; the second pertains to a cycle of sixty years, of which each year has a special name. In all Eastern Asia, the system employed for the designation of the years is based upon the combination of the name of ten, kan, with one of the denominations of twelve, chi. The cycle formed by a combination of this character may be found in Japan, Manchooria, Mongolia, and Thibet. The Aztec cycle of fifty-two years, formed of two smaller cycles of four and thirteen years, led Humboldt to suggest that Asiatic ideas might have penetrated to Mexico. Sometimes, but rarely, the Asiatics count by cycles of twelve years, each of which has the name of an animal.

The lunar-solar year of the Hindoos was based on a sidereal solar year of which the twelve months, of unequal length, had a duration exactly defined. The solar month Chaîtra consisted of 30 days, 20 hours, 21 minutes, 2 seconds, and 36 thirds, the day being divided into sixty hours. The year began with the new moon preceding the beginning of the solar year. When two lunar months began within the same solar month, the first one was intercalated. If no lunar month began in the course of a particular solar month, the year lost an ordinary month, but two intermediate months were added. Every Hindoo month has a particular name, and the new moons, which serve to fix the beginnings of the months and the years, are calculated with so great precision that it is much more easy to identify an ancient date in India than in China. But some difficulties arise out of the use of different systems in ancient times, and also from the fact that the Hindoo day is the thirtieth part of the lunar month, which consists of twenty-nine days and a half, and is consequently shorter than the natural day.

The computation of the years begins with zero, the first year counting as 0, the second as 1, and so on. Each year bears a particular name appertaining to a cycle of sixty years, which is, however, different from the Chinese cycle, and is based on the course of the planet Jupiter, which performs its revolution in 11·86 years, or, in round numbers, twelve years. The Hindoo cycle is therefore equivalent to five Jovian revolutions and of a year ($$10\cdot 86\ \text{years} \times 5 = 59 \cdot 30\ \text{years}$$); in three