« AnteriorContinuar »
EVERY thing that relates to the sun is of such importance to man, that in all things he claims a natural pre-eminence. The sun is at once the most beautiful emblem of the Supreme Being, and under his influence, the fostering parent of worlds ; being present to them by his rays, cheering them by his countenance, cherishing them by his heat, adqrning them at each returning spring vith the gayest and richest attire, illuminating them with his light, and feeding the lamp of life.
To the ancients, he was known under a variety of names, each characteristic of his different effects; he was their Hercules, the great deliverer, the restorer of light out of darkness, the dispenser of good, continually labouring for the happiness of a depraved
He was the Mithra of the Persians, a word derived from love, or mercy, because the whole world is cherished by him, and feels, as it were, the effects of his love.
In the sacred scriptures, the original source of all emblematical writings, our Lord is called our sun, and the sun of righteousness; and as there is but one sun in the heavens, so there is but one true God, the maker and redeemer of all things, the light of the understanding, and the life of the soul.
As in scripture our God is spoken of as a shield and buckler, so the sun is characterized by this mark 0, representing a shield or buckler, the middle point the umbo, or boss ; because it is love, or life, which alone can protect from fear and death.
His celestial rays, like those of the sun, take their circuit round the earth; there is no corner of it so remote as to be without the reach of their vivifying and penetrating power. As the material light is always ready to run its heavenly race, and daily issues forth with renewed vigour, like an invincible cham-pion, still fresh to labour; so likewise did our redeeming God rejoice to run his glorious race, he excelled in strength, and triumphed, and continues to triumph over all the powers of darkness, and is ever manifesto ing himself as the deliverer, the protector, the friend, and father of the human race. *
PROBLEM II. To rectify the Celestial Globe.
To rectify the celestial globe, is to put it in that position in which it may represent exactly the apparent motions of the heavens.
* Ilorne, on the Psalms,
In different places the position will vary, and that according to the different latitudes of the places. Therefore, to rectify for any place, find, first, by the terrestrial globe, the latitude of that place.
The latitude of the place being found in degrees, elevate the pole of the celestial globe the same number of degrees and minutes above the plane of the horizon, for this is the name given to the broad paper circle, in the use of the celestial globe.
Thus, the latitude of London being 51 degrees, iet the globe be moved till the plane of the horizon cuts the meridian in that point.
The next rectification is for the sun's place, which
may be performed as directed in Prob. xxix; or look for the day of the month close under the ecliptic line, against which is the sun's place ; place the artificial-sun, or small paper patch, over that point, then bring the sun's place to the graduated edge of the strong brazen meridian, and set the hour index to the most elevated XII.
Thus, on the 24th of May the sun is in 3 de grees of Gemini, and is situated near the Bull's
eye and the seven stars, which are not then visible on account of his superior light. If the sun were on that day to suffer a total eclipse, these stars would then be seen shining with their accustomed brightness.
Lastly. Set the meridian of the globe north and south by the compass.
And the globe will be rectified, or put into a similar position to the concave surface of the heavens, for the given latitude.
PROBLEM III. To find the right ascension and de
clination of the sun, for any day.
Bring the sun's place in the ecliptic for the given day to the meridian, and the degree of the meridian directly over it is the sun's declination, for that day at noon. The point of the equindctial cut by the meridian, when the sun's place is under it, will be the right ascension.
Thus, April 19, the sun's declination is 11° 14' north, his right ascension 27° 30'. On the first of December, the sun's declination is 21° 54' south, right ascension 247° 50'.
PROBLEM IV. To find the sun's oblique ascension and descension, its eastern and western amplitude, and time of rising and setting, on any given time, in any given place.
1. Rectify the globe for the latitude, the zenith, and the sun's place. 2. Bring the sun's place to the eastern side of the horizon; then the number of degrees intercepted between a degree of the equinoctial at the horizon, and the beginning of Aries is the sun's oblique ascension. 3. The number of degrees on the horizon intercepted between the east point and the sun's place, is the eastern or rising amplitude. 4. The hour shewn by the index is the time of sunrising. 5. Carry the sụn to the western side of the horizon, and you in the same manner obtain the
oblique descension, western amplitude, and time of setting. Thus, at London, May 1, The sun's oblique ascension
18° 48' Eastern amplitude Time of rising
4 h 40 m Oblique descension
257° 7' Western amplitude
9 Time of setting
7 h 4m
PROBLEM v. To find the sun's meridian altitude.
Rectify the globe for the latitude, zenith, and sun's place; and when the sun's place is in the meridian, the degrees between that point and the horizon are its meridian altitude. Thus, on May 17, at London, the meridian altitude of the sun is 57° 55'.
PROBLEM Ví. To find the length of any day in the year,
latitude not exceeding 66} degrees.
Elevate the celestial globe to the latitude, and set the centre of the artificial sun to his place upon the ecliptic line on the globe for the given day, and bring its centre to the strong brass meridian, placing the horary index to that XII which is most elevated; then turn the globe till the artificial sun cuts the eastern edge of the horizon, and the horary index will shew the time of sun-rising ; turn it to the western side, and you obtain the hour of sun-setting.
The length of the day and night will be obtained