152 ASTRONOMY. 
date would fall every seven years upon the same day of the week ; since, 
however, every fourth year is leap year this coincidence takes place every 
28 years, which form one solar cycle, the series beginning the ninth year 
s.c.; thus, in 1847, the solar cycle is VIII., that is, it is the eighth year of a 
sun cycle in the nineteenth century. 
The Lunar Cycle, the golden number, and the Epacts, serve to determine 
the phases of the moon, and occurrence of Easter. The lunar cycle is the 
series of years after which the new and full moons again fall upon the same 
day of the year. This cycle amounts to 19 years of 365} days, and the 
number of any year indicating its place in the cycle, is called the golden 
number. ‘This cycle was discovered by Meton, 480 8.c., and the golden 
number is the remainder after adding one to the number of years, and 
dividing by 19. The quotient indicates the number of lunar cycles which 
have elapsed since A.D. up to the given time. Should the golden number be 
one, then the new moon falls on Jan. 1. For the determination of the new 
moon of any other years, the Epacts are employed, or the number which, for 
every year, determines the age of the moon on New Year’s day, or 
gives the number of days by which the last new moon of the previous 
year preceded New Year’s day. Should the new moon fall on Jan. 1, then 
the Epact = 0. 
As the lunar year is 10 days, 15 hours, 11 minutes, 25 seconds, or, in 
round numbers, 11 days shorter than the solar, it follows that the Epacts 
increase annually by 11; so that if, in one year, the Epact was 23, in the 
following it would be 3, as the series commences with 1 after 30. The pas- 
sage from the last year of a lunar cycle to the first of the following, amounts. 
not to 11, but to 12 days, and is called the leap of the Epacts. This inter- 
calary day is necessary, from the fact that the lunar year is not quite 11 days 
shorter than the solar year. For the year 1847 the golden number is 5, and 
the Epact 14. Knowing the Epacts, it is possible in a perpetual calendar 
to determine immediately every day upon which new moon falls. Thus, for 
the Epact 14, of 1847, the first new moon falls on the 16th of January ; 
nevertheless, small errors cannot always be avoided, as, for instance, is the 
case in the year mentioned, when the first new moon actually occurs early 
on the 17th January, at 1 hour, 34 minutes. After the occurrence of the 
new moon, we can readily determine the remaining phases of the moon. 
RUSSO-GRECIAN CALENDAR. ‘ 
76. The calendar of the Russians and Greeks has, in respect to the 
months, weeks, main festivals, &c., the same arrangement as the Gregorian 
calendar; nevertheless, these nations have retained the Julian in its essen- 
tial features, that is, with respect to Easter and the festivals dependent upon 
it. They are, therefore, about, 13 days behind the Gregorian date now, and 
will, in 1900, be 14 days; so that in the present century, for example, when 
they have March Ist according to their calendar, it will be March 13th 
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