An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

46 TlE EARTH.
but not by 400, again of 365; and every year' divisible by 400,
of 366.
Thus the year 1838, not being divisible by four, contains 365
days, while 1836 and 1840 are leap years. Yet to make every
fourth year consist of 366 days would increase it too much by
about 4 of a day in 100 years; therefore every hundredth year
has only 365 days. Thus 1800, although divisible by 4, was
not a leap year, but a common year. But we have allowed a
whole day in a hundred years, whereas we ought to have allowed only three-fourths of a day. Hence, in 400 years we
should allow a day too much, and therefore we let the 400th
year remain a leap year. This rule involves an error of less
than a day in 4237 years.*. If the rule were extended by
making every year divisible by 4,000 (which would now consist of 366 days) to consist of 365 days, the error would not be
more than one day in 100,000 years.t
1 13. This reformation of the calendar was not adopted in
England until 1752, by which time the error in the Julian
calendar amounted to about 11 days. The year was brought
forward, by reckoning the 3d of September the 14th. Previous to that time the year began the 25th of March; but it was
now made to begin on the 1st of January, thus shortening the
preceding year, 1751, one quarter.:
1 4. As in the year 1582, the error in the Julian calendar
amounted to 10 days, and increased by 3 of a day in a century, at present the correction is 12 days; and the number of
the year will differ by one with respect to dates between the
1st of January and the 25th of March.
Eramples. General Washington was born Feb. 11, 1731,
old style; to what date does this correspond in new style?
As the date is the earlier part of the 18th century, the correction is 11 days, which makes the birthday fall on the 22d':I Woodhouse, p. 874. t Herschel's Ast., p. 384.
t Russia, and the Greek Church generally, adhere to the old style. In order
to make the Russian dates correspond to ours, we must add to them 12 days.
France and other Catholic countries, adopted the Gregorian calendar soon after
it was promulgated.