826 THE POPULAR SCIENCE MONTHLY. 



countries, however, where continued clearness" of the sky was not 

 afforded, or where the necessity was urgently felt for a regular deter- 

 mination of future dates, the seers at length desired that they be per- 

 mitted 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 succes- 

 sion 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 " call- 

 ing 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 ap- 

 proximate 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 ob- 

 servation of men at an early time, and the knowledge of the recur- 

 rence 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 asso- 

 ciated 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 observa- 

 tions 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 recog- 

 nized with the naked eye ; and, since the light of the sun far super- 

 sedes that of the brightest fixed star, these observations could be made 



