The altar of Heaven at Peking consists of three circular marble terraces, the uppermost of which is paved with eighty-one stones arranged in circles. It is on a round stone in the centre of these circles that the Emperor kneels and is considered to occupy the centre of the earth. In the worship of Heaven, offerings are made to the heavenly bodies, the Sun, Moon, the Pole-star, Great Bear, five planets and twenty-eight constellations. The worship at the altar of Earth consists of offerings to the mountains, rivers and seas. This arrangement is strikingly unlike that of the ancient Mexicans, who associated the sun only with the Above, the male principle and the blue heaven, and worshipped the nocturnal heaven, the moon and stars, with the earth, darkness and the female principle. It is interesting to note the marked effect, produced by the two different modes of classification, upon the subsequent development of the state religions of China and Mexico. In the latter country where the contrast of light and darkness and of the duality of nature seems to have been most powerfully felt, the gradual institution, on a footing of equality of a diurnal masculine and nocturnal feminine cult or of a separate sun and moon worship, led to the formation of two equally powerful castes of priest-astronomers who devised their respective calendars and cults and ultimately stood in open rivalry and antagonism towards each other, as children of heaven and light: sun worshippers; and children of earth and darkness: moon worshippers. In China, as the cult of earth was subordinate from the first and all heavenly bodies were included in the worship of Heaven, there was no opportunity for any rivalry to develop in the superior caste of astronomers who jointly ruled, instituted their calendar and altered it under influences emanating from India. Heaven and Earth were jointly worshipped at the same altar until A.D. 1531, when it was decreed that there should be separate altars and that the worship of Earth should be separately conducted (Edkins). At the same time, while the Emperor acts as the high-priest of Heaven, we find associated with him, from remote antiquity, the Empress, the representative of the Earth-mother.