Page:Popular Science Monthly Volume 22.djvu/846

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countries, however, where continued clearness of the sky was not afforded, or where the necessity was urgently felt for a regular determination of future dates, the seers at length desired that they be permitted to calculate, upon the basis of the past determinations of the duration of the regular months, the recurrence of the phases of the moon for a certain time in advance, and therewith the regular succession of the months, and to publicly record the number and the method of counting the days of the single months. Thus, in place of the public proclamation from the house-tops of the observed appearances, the calendar now came into use, containing calculations of the "calling days."

Gradually, however, when after a length of time the new light of the moon failed to appear at the specified date, in consequence of the imperfection of the calendar's determination, the proclaiming was entirely abandoned, and the moon in the calendar became more the standard for reckoning time than the moon in the heavens. It was repeatedly sought to compensate for these variations by revision of the calendar; but the more accurate methods for computing time, which gradually came into general use, soon supplanted the lunar chronology, and the months retained in their duration simply an approximate relation to the lunar month of twenty-nine and a half days, and were finally apportioned as twelve nearly equal divisions of the year.

The solar year, as a great heat-period, naturally attracted the observation of men at an early time, and the knowledge of the recurrence of the same degree of warmth was early recognized as of great importance to the interests and progress of agriculture and navigation. As a period, however, for the reckoning of the days the year was too long, and it was only with the advance of science that it gradually attained to chronological significance, namely, as a large and suitable unit of time for the division into months and days. The recurrence of similar phases of the year and evolution of heat were next associated each time with the appearance of certain celestial phenomena, in like manner as the commencement of the month with the resuming of the moon, and these observations were intrusted to individuals, who either proclaimed or published them. A common yearly calendar was thus prepared in advance, upon the basis of long and careful observations of the times of the recurrence of these phenomena, giving the days of certain months of each year on which they were to be seen, the changes of weather which would then take place, and these days were to form the reckoning points of time.

These phenomena in the heavens from which the data were derived were those positions of the sun in the sky, at certain intervals, relative to some fixed star or constellation, which could be most readily recognized with the naked eye; and, since the light of the sun far supersedes that of the brightest fixed star, these observations could be made