COMMON THINGS THE ALMANAC. 



phases, that is for conjunction, quadratures, and opposition, or as 

 it is otherwise and more commonly expressed for the new moon, 

 the first quarter, the full moon, and the last quarter. 



Thus, for example, when we find the moon's age on any proposed 

 day given as 0'6, it is to be understood that at the civil or mean 

 noon of that day, the time elapsed since the moment of conjunc- 

 tion was six-tenths of a day or 14 hours and 24 minutes. Again, 

 if the age set down were 17 '2, it is meant that at the noon of the 

 day proposed an interval of 17 days and two-tenths of a day, 

 that is 17 days 4 hours and 48 minutes, had elapsed since the 

 moment of new moon. 



88. By comparing together the dates of the successive phases 

 of the moon as given in the almanack in each lunar month, and 

 by comparing one with another the dates of the successive new 

 moons, it will be found that the moon's motion during each lunar 

 month is subject to considerable variation, and also that the length 

 of the lunar month itself is very variable. 



To render this manifest it will only be necessary to take from 

 the almanack the dates of the phases during a lunar month, and 

 the dates of the new moons during a year, and to compare them 

 together. 



Thus for example in the almanack for 1855 we find the follow- 

 ing dates for the successive phases of the moon which was new on 

 the 16th February. 



H. M. S. 



New Moon . . . February 16, at 6 47 30 p.m. 



First Quarter . . . February 23, at 5 33 42 ,, 



Full Moon .... March 3, at 10 8 



Last Quarter .... March 11, at 1 59 18 



New Moon . ... . March 18, at 4 45 12 a.m. 



From which it follows that the intervals between the successive 

 phases were 



D. H. M. S. 



From New Moon to First Quarter . , G 22 46 12 



From First Quarter to Full Moon . .. 8 4 34 18 



From Full Moon to Last Quarter . . . 7 15 51 18 



From Last Quarter to New Moon . .. 6 14 45 54 



29 9 57 42 



Thus it appears that so far from the rate of the moon's apparent 

 motion relatively to that of the sun being uniform through a 

 lunar month, it is subject to so considerable a variation that while 

 the first quarter is made in little more than 6 days 22| hours, the 

 second is only completed in 8 days and 4 hours. 



If we compare the lengths of the successive lunar months we 

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