it would be if the earth stood quite still,
always remaining in one place as the melon
does. Moreover, the earth's orbit is not
exactly circular, but elliptical or oval; and
that causes a difference in the intervals of
time between the successive presentations of
the same meridian to the sun. And so
astronomers have contrived a fictitious day,
regulated by the apparent movement of a fictitious
sun, by which all days are regulated to be
twenty-four hours long alike. There is therefore
real or natural time, and mean or artificial
time. The first is ascertained by observations
of the sun; the second is known
either by adding to, or subtracting from, real
time certain numbers that are given in tables
adapted to every day in the year, or by merely
looking at a good chronometer. The better
the clock and the better the sun-dial, the more
certain will be their disagreement at particular
well-known times of the year. Indeed,
they agree only four times in the year. The
amount needed to reconcile them, is what is
called the equation of time, and is often
printed in almanacs for the million as Clock
before Sun, or Sun before Clock, as the case
may be. Note well, therefore, that, in
consequence of the earth's revolution round the
sun, a day is not the return of the same rib
or meridian to exactly the same relative
point. It would be so if the earth stood still,
like the melon before the fire; but, in
consequence of her advance in her orbit, the
completion of an entire revolution on her axis
does not precisely coincide with the presentation
of the same meridian to the sun.

The lapse of time occupied by a complete
revolution of the earth on her axis (which
coincides with the passage of the same fixed
star across the same meridian, because the
fixed stars are at such enormous distances
from us that the earth's diameter and even
the diameter of the earth's orbit are as
nothing, and insensible, in comparison) is
called a sidereal day, from siderealis, belonging
to stars. The sidereal day is a most valuable
unity of time, for it never varies from century
to century, and is the same from whatever
spot on earth it is observed. The sidereal
day, which is the time of apparent revolution
of the celestial sphere, is a trifle shorter than
the mean solar day, consisting of only twenty-
three hours, odd minutes, and seconds, of
mean solar time. In fact, the earth clearly
cheats herself out of a day by the performance
of her journey round the sun: if she
stood still with reference to the sun, as she
virtually stands still with reference to the
fixed stars, she would have one sunrise more
than she has under actual circumstances.
From the comparative shortness of the sidereal
day, it follows that the same star may
cross the same meridian in the same solar
day—which will happen to the Pole-star on
the seventh of April next.

Our day called the civil day, begins at
midnight, or at the sun's passage across the
lower or opposite meridian to our own.
The astronomical day, adopted by modern
men of science, begins at noon; twelve
hours after the civil day. The ecclesiastical
day, regulating religious observances, agrees
in its commencement with the civil day.
When Hannah More brought about the
closing of the opera at twelve o'clock, on
Saturday nights, her scruples were guided by
the civil not the astronomical day. A strict
and rigid astronomer would have
unhesitatingly allowed the ballet-dancers to
continue their evolutions until broad daylight.
The above considerations suggest the thought
that it is not quite so easy as is generally
supposed to say Good morning precisely at
the right moment.

All these points are precise, and can be
clearly laid down and comprehended by the
exertion of a little attention; unfortunately,
such is not the case with our Moveable Feasts,
which are what they are, dependent on a
sliding scale, in consequence of the deficiency
of historic facts. There would have been no
Moveable Feasts in our calendar, if the day
on which Easter ought to fall had been
accurately known. The Church never knew the
exact date of the death of Jesus Christ;
only, there existed a tradition according to
which, the Resurrection took place shortly
after the vernal equinox and after a full moon.

In the year three hundred and twenty-five,
when the Council of Nicæa assembled to
regulate the constitution of Christian worship,
it had to fix the epochs of the celebration of
the feasts—amongst which Easter, that is to
say the anniversary of the Resurrection of
Christ—was the principal, and the one on
which depended the return of several other
first-class feasts, such as the Ascension,
Whitsuntide, Trinity Sunday, and the rest;
for the true dates of the Ascension and of
Pentecost were no better ascertained than
that of Easter.

Christian tradition held that the first
took place forty days, and the second fifty
days, after Easter. It was therefore of great
importance that the fathers of the Council
should carefully regulate the date of this
latter feast, because it must be followed forty
days afterwards by Pentecost. They were
thus obliged to fix the date of Easter, for
which they had no date; and, at that epoch,
they were in possession of no means of
accurately calculating the movements of the
heavenly bodies. Moreover, the astronomical
facts which tradition was able to supply, were
too vague to serve as a basis for the solution
of the problem. In the impossibility of
overcoming the difficulty, they evaded it; and
determined that, "Every year, the Feast of
Easter should be celebrated on the Sunday
which follows the day of the first full moon,
happening after the twentieth of March."
Nevertheless, Clavius acknowledges that, in
fifteen hundred and eighty-two, the Church
might have exercised the right of depriving