The solar calendar above described might have answered all the purposes of the people; but the priests chose to construct another for themselves. This was called a “lunar reckoning,” though nowise accommodated to the revolutions of the moon.[191] It was formed, also, of two periodical series, one of them consisting of thirteen numerical signs, or dots, the other, of the twenty hieroglyphics of the days. But, as the product of these combinations would be only 260, and as some confusion might arise from the repetition of the same terms for the remaining 105 days of the year, they invented a third series, consisting of nine additional hieroglyphics, which, alternating with the two preceding series, rendered it impossible that the three should coincide twice in the same year, or indeed in less than 2340 days; since 20 × 13 × 9 = 2340.[192] Thirteen was a mystic number, of frequent use in their tables.[193] Why they resorted to that of nine, on this occasion, is not so clear.[194] This second calendar rouses a holy indignation in the early Spanish missionaries, and Father Sahagun loudly condemns it, as “most unhallowed, since it is founded neither on natural reason, nor on the influence of the planets, nor on the true course of the year; but is plainly the work of necromancy, and the fruit of a compact with the Devil!”[195] One may doubt whether the superstition of those who invented the scheme was greater than that of those who thus impugned it. At all events, we may, without having recourse to supernatural agency, find in the human heart a sufficient explanation of its origin; in that love of power, that has led the priesthood of many a faith to affect a mystery the key to which was in their own keeping. By means of this calendar, the Aztec priests kept their own records, regulated the festivals and seasons of sacrifice, and made all their astrological calculations.[196] The false science of astrology is natural to a state of society partially civilized, where the mind, impatient of the slow and cautious examination by which alone it can arrive at truth, launches at once into the regions of speculation, and rashly attempts to lift the veil--the impenetrable veil--which is drawn around the mysteries of nature. It is the characteristic of true science to discern the impassable, but not very obvious, limits which divide the province of reason from that of speculation. Such knowledge comes tardily. How many ages have rolled away, in which powers that, rightly directed, might have revealed the great laws of nature, have been wasted in brilliant but barren reveries on alchemy and astrology!