GLOBES. 
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meridian, already described ; the equinoc- 
tial. as it is called on the celestial, and equa- 
tor on the terrestrial globe ; the ecliptic 
drawn along the middle of the zodiac ; and the 
two colures. The lesser circles, of principal 
use, are the two tropics and the two polar 
circles. Of these circles some are fixed, and 
always obtain the same position ; others 
moveable, according to the position of the 
observer. The fixed circles are the equator 
and ecliptic, with their parallels and secon- 
daries ; which are usually delineated upon 
the' surface of the globes*. The moveable 
circles are the horizon, with its parallels and 
secondaries. 
The horizon is that great and broad wooden 
circle surrounding the globe, and dividing it 
into two equal parts, called the upper and 
lower hemispheres. It has two notches, to 
Jet Hie brazen meridian slip up and down, 
according to the different heights of the pole. 
On the fiat side of this circle are described 
the twelve signs, the months of the year, the 
points of the compass, &c. The brazen me- 
ridian is an annulus or ring of brass, divided 
into degrees. It divides the globe into two 
equal parts, called the eastern and western 
hemispheres. The quadrant of altitude is 
a thin pliable plate of brass, answering ex- 
actly to a quadrant of the meridian. It is 
divided into 90°, and has a notch, nut and 
screw, to fix to the brazen meridian in the 
zenith of any place, where it turns round a 
.pivot, and supplies the room of vertical cir- 
cles. The hour-circle is a fiat ring of brass, 
divided into 24 equal parts or hour-distances; 
and on the pole of the globe is fixed an index 
that turns round with the globe, and points out 
the hours upon the hour-circle. Lastly, there 
are generally added a compass and needle 
upon the pediment of the frame. 
The surface of the celestial globe may be 
esteemed a just representation of the concave i 
expanse of the heavens, notwithstanding its j 
convexity ; for it is easy to conceive the eye 
placed in the centre of the globe, and view- 
ing the stars on its surface, supposing it made 
.of glass, as some globes are: also that it holes 
were made in the centre of each star, the eve 
in the centre of the globe, properly placed, 
would view through each of the holes the 
very stars in the heavens represented by them. 
As it would be impossible to have any di- 
stinct notion of the stars, in respect to their 
number, order, and distances, without ar- 
ranging them in certain forms, called con- 
stellations, this tin* first observers of the hea- 
vens took care to do; and these, like king- 
doms and countries upon the terrestrial globe, 
serve to distinguish the different parts of the 
superficies of the. celestial globe. The stars, 
therefore, are all disposed in constellations 
under the forms of various animals, whose 
names and figures are represented on the j 
celestial gh>be, which were first invented by I 
the antient astronomers and poets, and are 
still retained for the better distinction of these 
luminaries. 
PROBLEMS ON THE CELESTIAL GLOBE. 
1. To rectify the globe: that is, to place it 
in such a particular situation as is necessary 
for the solution of many problems. Raise or 
elevate the pole to the latitude of the place ; 
screw the quadrant of altitude in the zenit h ; 
set the index of the hour-circle to the upper 
xu, and place the globe north and south by 
the compass and needle ; then it is a just re- 
presentation of the heavens for the given 
day at noon. 
2. To find the sun's place in the ecliptic. 
Find the day of the month in the calendar on 
the horizon, and right against it is the degree 
of the ecliptic which the sun is in for that 
day. 
3. To find the sun's declination. Rectify 
the glofte, bring the sun’s place in the eclip- 
tic to the meridian, and that degree which it 
cuts in the meridian is the declination re- 
quired. 
4. To find the sun's right ascension. Bring 
the sun’s place to the meridian, and the de- 
gree of the equinoctial cut by the meridian 
is the right ascension required. 
5. To find the sun's amplitude. Bring the 
sun’s place to the horizon, and the arch of 
the horizon intercepted between it and the 
east or west point, is the amplitude, north or 
south. 
6. To find the sun's amplitude for any 
given day and hour. Bring the sun’s place 
to the meridian, set the hour-index to the 
upper xn ; then turn the globe till the index 
points to the given hour, where let it stand ; 
then screwing the quadrant of altitude in the 
zenith, lay it over the sun’s place, and the 
arch contained between it and the horizon 
will give the degrees of altitude required. 
7. To find the sun’s azimuth for any hour 
of the day. Every thing being done as in 
the last problem, the arch of the horizon 
contained between the north point and that 
where the quadrant of altitude cuts it, is the 
azimuth east or west as required. 
8. To find the time when the sun rises or 
sets. Find the sun’s place for the given day, 
bring it to the meridian, and set the hour- 
hand to xii ; then turn the globe till the 
sun’s place touches the east part of the hori- 
zon, die index will shew the hour of its ris- 
ing; after that, turn the globe to the west 
part of the horizon, .and the index will shew 
the time of its setting for the given day. 
9. To find the length of any given day or 
night. This is easily known by taking the 
number of hours between the rising and set- 
ting of the sun for the length of the day ; and 
the residue to 24, for the length of the night. 
)0. To find the hour of the day , having the 
sun’s altitude given. Bring the sun’s place 
to the meridian, and set the hour-hand to 
xn; then turn the globe in such a manner, 
( that the sun’s place may move along by the 
j quadrant of altitude (fixed in the zenith) til! 
I it touches the degree of the given altitude, 
where stop it, and the index will shew on the 
horary circle the hour required. 
11. To find the place oj the moon, or any 
planet, for any given day. Take \\ hite’s 
Ephemeris, and against the given day of the 
month vou will find the degree and minute 
of the sign w hich the moon or planet pos- 
sesses at noon, under the title of geocentric 
motions. The degree thus found being 
marked in the ecliptic on the globe by a 
small notch or otherwise, you may then pro- 
ceed to find the declination, right ascension, 
latitude, longitude, altitude, azimuth, rising, 
southing, setting, &c. in the same manner as 
has been shewn for the sun. 
1 2. To explain the plucnomena of the har- 
vest moon. In order to this we need only 
consider, that when the sun is in the begin- 
[ mng of Aries, the full moon on that day must 
be in the beginning of Libra : and since, 
when the sun sets or moon rises cu that dclv, 
those equinoctial points will be in the hori- 
zon, and the ecliptic will. then be least of all 
inclined thereto, the part or arch which the 
moon describes in one day, viz. 13 e , will take 
up about an hour and a quarter ascending 
above the horizon ; and, therefore, so long 
will be the time after sun-set, the next night, 
before the moon will rise. But at the oppo- 
site time of the year, w hen the sun is in the 
autumnal, and the full moon in the vernal, 
equinox, the ecliptic will, when the sun is 
setting, have the greatest inclination to the 
horizon; and, therefore, 13° will in this case 
soon ascend, viz. in about a quarter of an 
hour; and so long after sun-set will the moon 
rise the next clay after the full: whence, at 
this time of the year, there is much more 
moonlight than in the spring; and hence this 
autumnal full moon came to be called the 
harvest moon, the hunter’s or shepherd’s 
moon ; all which maybe clearly shewn on the 
globe. 
13. To represent the face of the starry fir- 
mament for any given hour of the night. 
Rectify the globe, and turn it about till tlie 
index points to the given hour ; then will all 
the upper hemisphere of the globe represent 
the visible half of the heavens, and all the 
stars on the globe will be in such situations 
as exactly correspond to those in the hea- 
vens, which may therefore be easily found, 
as will be shewn in the lblh problem. 
14. To find the hour when any known star 
will rise, or come upon the meridian. Rec- 
tify the globe, and set the index to xii; then 
turn the globe till the star comes to the ho- 
rizon or meridian, and the index will shew 
the hour required. 
15. To find at what time of the year any 
given star will he on the meridian at xii at 
night. Bring the star to the meridian, and 
observe what degree of the ecliptic is on the 
north meridian under the horizon; then find 
in the calendar on the horizon the day of the 
year against that degree, and it w ill be the 
day required. 
It). To find any particular star. First find 
its altitude in the heavens by a quadrant, and 
the point of the compass it bears on; then, 
the globe being rectified, and the index turn- 
ed to the given hour, if the quadrant of alti- 
tude is fixed on the zenith, and laid towards 
the point of the compass on which the star 
was observed, the star required will he found 
at the same degree of altitude on the said 
quadrant, as it w as by observation in the 
heavens. 
PROBLEMS ON THE TERRESTRIAL GLOBE. 
1 . To find the latitude of any place. Bring 
the given place to the brazen meridian, and 
observe what degree it is under, for that is 
the latitude required. 
2. To rectify the globe for any given place. 
Raise the pole so many degrees above the 
horizon as are equal to the latitude of the 
place; then, finding the sun’s place, bring it 
to the meridian, and proceed as directed in 
problem 1. on the celestial globe. 
3. To find the longitude of a given place. 
Bring the place to the brazen meridian, and 
observe the degree of the equator under the 
same, for that expresses the longitude re-* 
quirecl 
