« ElőzőTovább »
this, and also the dominical letter, we might readily insert ; but as they require some calculation, most of our readers will probably prefer a table that renders the finding of Easter Sunday very easy, from the present period to the year 1900. - Epacts. Paschal full Moons. || Epacts. Paschal full Moons. x. 13th April ---E
4th April ...C xi. 2d April « . - A xx. 24th March --F xxii. 12th March --D
12th April - •.D 10th April - ..B
1st April - .. G xiv. 30th March - - E
21st March 18th April - ..C
9th April - vi. 7th April - . -F
29th March -. 27th March - - B
17th April ... xvii. | 15th April - .. G ||
6th April - . - E xvii 26th March .. A
We have already shown that the epact is found by means of the golden number ; thus, for the year 1814,
(1814 + 1 = 95 and 10 over
.10–1X11 – 3 and 9 over 9. The epact is ( 30
I To find the dominical letter for any year.–Rule : Divide the hundreds of the given year by 4, and subtract twice the remainder from 6; then the sum of this last remainder, the odd years, and their fourth, divided by 7, will leave a remainder. which, being deducted from 7, shows the index of the dominical letter. Thus, for the year 1814,
s from 6 leaves 2.'
and 7-5= 2.
19 Two, then, is the index of the dominical letter; and as 1 is the index of A, 2 must be the index of B, which is the dominical letter for the year 1814.
Now to find Easter with these data and the foregoing table : we have the epact 9, which corresponds with the 4th of April, whose weekly letter is c, but the Sunday letter of 1814 is B; therefore the first Sunday B, after the 4th of April с, will be on the 10th of April, which is Easter Sunday.
Having obtained Easter-day, the other feasts are easily calculated, thus :
Epiphany, or Twelfth-day, is always on the 6th of January. :
Easter term begins a fortvight after the Wednesday in Easter. week.
Rogation Sunday is 6 weeks after Easter.
Trinity term begins the Friday after Trinity Sunday, and ends on the Wednesday fortnight after.
The beginning and end of Hilary and Michaelmas terms are fixed.
Advent is always the Sunday nearest the 30th of November, whether before or after; and the Sundays after Trinity, marked in the calendar, are those between Trinity Sunday and Advent Sunday.
The rising and setting of the Sun for certain days in the month of May will be as follow: Sunday, 1st, Sun rises 37 m. past 4. Sun sets 23 m. past 7 Wednesday, 11th, --.- 20.-- - 4 -•.- 40••••7 Saturday, 21st, ---- 6 ---4 -.-- 54• • .-7
The Sun enters the sign Gemini at 36 m. past 6 in the afternoon of the 21st. Saturn is stationary on the 11th. Mars eclipses the star marked 132 8, passing nearly over the centre ; and again, on the 27th, it eclipses & I 54' north of the centre. .
Equation of Time. (See January.] The following table will show what is to be subtracted from the apparent time as marked on the dial to obtain equal or true time for each fifth day during the month of May :
m. S. Sunday, -, May 1, from the time by the dial subtract. 3:2 Friday, .....
- -3 35 Wednesday, -- 11, - - - - - - - - - - - • 3 54 Monday, ---- 16, - - - • - - - - . . . - 3 58 Saturday, --.- 21, - - - • - - - - : 3: 48 Thursday, -- • 26, - - -
- - 3 24 Tuesday, - .-• 31, • - • - - - - - - - - 2 49
The Moon is full at 29 m. past 10 in the morning of the 4th: it enters its last quarter at 41 m. past 2 in the afternoon: the change, or new Moon, is at 23 m. past 4 on the 19th, and it enters its first quarter at 31 m, after 7 in the morning of the 26th. The time of the Moon's rising for the first 4 days after it is full is as follows :May 5th, •.., 36 m. past 8 in the afternoon. .
6th, • • - - • 4% -.-9-; ditto,
8th, - ... - 4% - 11 - ... ditto. Venus will be at her greatest elongation on the 21st day of the month. Jupiter will be in the quadrature at į past 11 at night on the 22d, and the Georgian planet. will be in opposition to the Sun, that is at the distance of six signs, or the two bodies will be in opposite parts of the heavens, at 6 in the morning of the 22d day of the month.
There will be only two'eclipses of Jupiter's first satellite visible at Greenwich this month; namely, on the
7th day, at 10 minutes past 12 at night.
Of the Earth. The earth on which we live is, unquestionably, a primary planet belonging to the solar system, and which like Mercury and Venus already described, and Mars, Jupiter, Saturn, and the Georgian planets, the subjects of future notice, depends on the Sun for its light and motion.
wests appearakens, in which all
In the darker ages of antiquity, this vast body, the abode of life and happiness to countless millions of creatures, was considered as a large circular plane spreading out indefinitely on all sides : and the surrounding heavens, in which the Sun, Moon, and stars, appear to move every 24 hours from east to west, were imagined to be at no great distance from it, and to have been created solely for the use and ornament of the inhabitants of the earth. It is now, - and has for centuries, been completely ascertained
that the earth is of a spherical figure, nearly resem-: bling an artificial globe.
The several proofs of the sphericity of the earth are as follow : (1) Several celebrated navigators, as Ma.. gellan, Sir Francis Drake, Lord Anson, and Captain Cook, have actually sailed round it, by setting out, for instance, at Plymouth or other places, and by continually steering their course in one direction, viz. westward, have, at length, arrived at the place from which they had departed; which could never have happened, had the earth been of any other than a spherical form. (2) This form is also evident, from the circular appearance of the sea, and the circumstances which attend large objects, when seen at a distance on its surface. For, as has been observed a thousand times, when a ship goes out to sea, the people on the surrounding shore first lose sight of the hull, or body of the vessel, afterwards of the rigging, and at last they only discern the topmast, which circumstances can only be explained by supposing the convexity of the water between the eye and the object; for if it were not so, the image of the largest and most conspicuous part of the vessel would remain longest on the eye. (3) Another proof is taken from the shadow of the earth upon the face of the Moon, in the time of a lunar eclipse. For the Moon, like the earth, having no light but what it receives from the Sun, and the earth being, at this time, interposed exactly between them, the Moon
must either, wholly or in part become obscure : and since in every eclipse of this kind, which is not total, the obscure part always appears to be bounded by a circular line, hence it is inferred the earth is spherical, it being certain that none but a spherical body can, in all situations, cast a circular shadow. To
There are three principal motions belonging to the earth, viz. a motion of rotation about its axis, a mo, tion in an orbit round the Sun, and a motion of its axis round the poles of the ecliptic. These three motions are derived from a single impulsion, supposed to be given to the earth at its origin, and combined with the perpetual action of the Sun. The rotation of the earth on its axis, called its, diurnal motion, is the most uniform motion with which we are acquainted: it is performed in 23 h, 56 m. 4. sec.
The earth, or, to speak with more accuracy, the centre of gravity of the earth and Moon, describes an orbit round the Sun, which onbit is not of a circu. lar but elliptic form, the Sun being in one of the foci. If we suppose the plane of this orbit extended to the fixed stars, it will then trace the path in the heavens called the ecliptic. The earth does not move round this orbit in a perpendicular position, but inclined to the ecliptic in an angle of 23° 28'. The points in the earth's orbit, which are intersected by this plane, are called the equinoctial points. The motion of the earth in its orbit is not uniform ; it depends on its distance from the Sun: when it is nearest that body, in winter, it moves the fastest, and it moves the slowest when it is farthest from the Sun in summer. It is, however, so far regular, that, with the exception of some trifling, inequalities caused by the action of the Moon and planets, the radius-vector, as it is called, or line joining the centres of the earth and Sun, describes equal areas of the ellipse in equal times.
The third motion belonging to the earth is that which produces the precession of the equinoxes.