156 
Mathemati- Jure, TC the tropic of Cancer, T’C’ the tropic of Capri- 
cal Geogra- egry, AP the arctic circle, and A’P’ the antarctic circle. 
Phy "The meridian AENQS is graduated in the same way, as 
the brazen meridian of the celestial globe, viz. from 
towards N and §, and from N and S tsweaae Q; and 
the horizon is moveable, so that by raising or depressing 
jt at thenorth and south points, it may be made to in- 
tersect the meridian INQS, in any two opposite points. 
The whole instrument rests on the southern extremity S$ 
of the axis, and is generally so constructed that the earth 
G, with the meridian AENQS, and. horizon HR, may 
be made to revolve from west to east, while the other 
circles remain at rest ; or the latter may be made to re- 
volve from east to west, while the former remain fixed. 
By means of the joint B, the sphere may be placed so 
as that the north pole N may have any elevation, the 
angle of that elevation being measured by the gradua- 
ted arch F, attached to BS, and passing through a slit 
in BD. In using the celestial globe, then, the eye is 
supposed to be situated on G, and viewing the circles 
of the armillary sphere, the latter in all cases being 
placed in the same situation with the globe. 
Sect. II. Solution of Problems by the Globes. 
I. By the Celestial Globe. 
Pros. L—To rectify the globe for any place, that is, 
to give the globe the same position, as the celestial sphere 
has, to a spectator at any place on the earth’s surface. 
Elevate the north or south pole, according as the place 
is north or south of the equator, till its altitude be equal 
to the latitude of the place. 
Pros. IJ.—To find the sun’s longitude, or place in 
the ecliptic, for any given day. 
Find the day under the ecliptic on the globe, and 
opposite to it will be the sign and degree required. The 
. problem may also be solved, by finding the day in the 
calendar on the wooden horizon, marking the sign and 
degree mo to it, and finding the same sign and de- 
gree in the cg on the globe. As the sun is always 
in the ecliptic, he has no latitude. 
Pros. IfI.—To find the sun’s right ascension and 
declination for any given day. 
Bring the’sun’s place in the ecliptic to the graduated 
edge of the brazen meridian, then the degree of the 
equator under the meridian will shew his right ascen- 
sion, and the degree of the meridian over his place will 
be his declination. When the sun’s declination is less 
than 23° 28’, there are two corresponding places in the 
ecliptic, which may be found by marking those two 
points on the ecliptic, which pass successively under 
the given declination on the meridian. 
Prog. 1V.—To dispose the celestial globe, so as to 
exhibit the actual appearance of the heavens at any gi- 
ven time and place. 
Rectify the globe for the latitude of the place, and 
bring the sun’s place in the ecliptic, and the 12th hour 
of the horary to the brazen meridian. Turn the globe 
towards the east or west, according as the time is be- 
fore or after noon, till the given hour on the hour circle 
comes to the meridian, and the globe will represent the 
actual ch eg of the heavens, at that time and place. 
Pros. V.—To find those stars that never rise, and 
those that never set, at a given place not under the 
equator. 
Rectify the globe for the latitude, and make it re- 
volve. he stars that do not sink below the wooden 
3 
To rectify 
the globe. 
To find the 
sun’s place. 
Fo find the 
sun’s right | 
ascension, 
&e 
To exhibit 
the appear- 
ance of the 
heavens. 
To find the 
stars that 
never rise, 
&a 
GEOGRAPHY. 
horizon, are those that never set, and the stars that do Math 
not appear above it, are those that never rise in that la- “al G 
titude. _ If the place be under the equator, every star _? 
is 12 hours above and 12 hours below the horizon. . ‘\ 
Pros. VI.—To find the right ascension and declina- To fin 
tion of a fixed star. : right” 
Bring the star to the brazen meridian, and its right ‘19+ 
ascension and declination will be found, as in Problem * 
III. 
Pros. VII.—The right ascension and. declination of To find 
a star being given, to find the star on the globe. oy star froy 
Bring the degree of the equinoctial ieabin the its right 
right ascension to the meridian, and the degree of the °°" 
meridian, denoting the declination, will be over the star. i 
Pros. VIII,—To find the longitude and latitude of To fina 
a given star. » longituc 
Place the upper extremity, or 90th degree of the qua- &¢- of 
drant of altitude, on the north or south pole of the eclip- *“" 
tic, according as the star is north or south of the eclip- 
tic, and let its graduated edge fall upon the star; then 
the degree of the ecliptic, intersected by the 
will be the longitude of the star, and the degree of the 
quadrant over the star, its latitude. ‘ 
Pros. IX.—The longitude and Jatitude of a star be- To fir 
ing given, to find the star upon the globe. _ star frop 
Place the extremity of the quadrant of altitude on the bot 7 
pole of the ecliptic, and make its graduated edge inter- "°° “ 
sect the ecliptic, in the longitude of the star ; then the 
star will be found, under the degree of the quadrant de~ 
noting its latitude. ; : 
Pros. X.—To find what stars are rising, setting, or To find 
culminating, at any given time and place, and also the what : 
altitude and azimuth of any star, at the same time and {°° ™ 
lace. ‘ 
, Dispose the globe as in Prob. IV. then the stars un- 
der the eastern side of the horizon are rising, those un- 
der the western side are setting, and those under the 
meridian are culminating. 
If the quadrant of altitude be fixed on the zenith, and To fin 
its graduated edge made to fall on a given star, the de- 7 
gree of the quadrant over the star, will be its altitude, ...., 
and the degree of the horizon intersected by the qua- 
drant its azimuth. 
Pros. XI.—To find when a given star rises, sets, or To fine 
culminates at any place on any given day. _ when j 
Dispose the globe and hour circle as in the first part ™*» ¢ 
of Prob. IV. then bring the star successively to the east- 
ern side of the heeiece, the EAR and western side 
of the horizon, and the times of its rising, culminating, i 
and setting on the hour circle, will come to the meri- 
dian respectively. “4 4 
distance To 
Pros. XII.—To find the apparent 
between two stars ; that is, the arch of the great circle angul: 
intercepted between them. , distang 
Apply the quadrant of altitude to the globe, so that bee 
its graduated edge may fall on both the stars, the zero, ~~ 
or commencement of the uation, being on one of 
them ; then the degree of the quadrant over the other 
will be the angular distance required, 
Pros. XIII.—To find when a planet rises, sets, or To fi 
culminates on any day: at a given p when 
Find the planet’s place on the globe, from its longi- 5¢t ™ 
tude and latitude, or right ascension and declination, as hog 
given in the Nautical Almanack, or any other epheme- 
ris, and fix on that place the mame or character of the 
planet ; then its rising, setting, or culminating, also its 
altitude, azimuth, &c. may be found in the same way 
as if it were a fixed star. In general, all the problems 
relative to the fixed stars are applicable to the planets, 
