S58 
V 
GEOGRAPHY. 
horizon or ecliptic, A circle is alfo laid down on the 
common terreftrial globe to reprefent the ecliptic, and 
to be 11 fed as fuch in folving problems upon the com¬ 
mon globes, though it involves numerous abfurdities : 
thus, having marked the fun’s place in the ecliptic, and 
re^lified the globe to the latitude, then turn the globe, 
and the fun and earth have a diurnal motion together j 
of courfe, if you have day when you begin, you will 
have the fame during the whole twenty-four hours ; or, 
vice verja, twenty-four hours of night. Several other 
impertedlions might eafily be adduced; but thefe are 
fufficient to fliew the defedt of their conftrudfion. 
The terrejlrial globe, reprefented in Plate I. fig. 2, does 
not hang in a frame like the common globes, but is 
mounted on a pedeftal, fupported by, and moveable 
on, an axis, whicli is inclined 66^ degrees to the eclip¬ 
tic, and of courl'e is always by this means parallel to 
tile axis of the earth, fuppeffing the path of the globe 
to be parallel to the ecliptic. On the pedeflal, but un¬ 
der tlie globe, is a graduated circle C D, marked with 
the figns and degrees of the ecliptic ; adjoining to which 
is a circle of months and days, anfwering to every de¬ 
gree of tlie ecliptic ; within this circle is the fun’s de¬ 
clination for every day of the montli. There is alfo a 
moveable arm AB, w'liich, being fet to the day of the 
month, immediately points out the fun’s place in the 
■ecliptic, and his declination. On this moveable arm, 
but near the index, is added a pillar E ; on the top of 
this pillar is fixed a fmall ball, through which a fteel 
v/ire pafTes, to reprefent a ray proceeding from the cen¬ 
tre of the fun. 
Round the whole globe is a brafs circle 1 ', to repre¬ 
fent the horizon of any place ; and at right angles to 
this horizon, is fixed a femicircle G, to anfwer fora ge¬ 
neral meridian. The middle point of this femicircle 
anfwers for the fituation of any inhabitant on the earth, 
for which reafon a fteel pin is fixed over the middle 
point of this femicircle. One fuppofitidn only is ne- 
cellary for performing every problem with this globe ; 
namely, that a fpherical luminous body will enlighten 
one half a fpherical opake body, and, confequently, 
that a circle at right angles to the central folar ray, and 
dividing the globe in half, will be a terminator, Ihew- 
ing the boundaries of light and darknefs for any given 
day. For this ptirpofe, at the end of the moveable arm 
oppofite to the fun, there is a pillar H, from the top of 
which projects a piece to carry a circle I, which allb 
/urrounds the globe, and always divides it into equal 
portions, feparating the enlightened from the dark parts. 
Eighteen degrees behind this circle, but parallel to it, 
is another circle, intended to reprefent the limits of 
twilight. 
There are two brafs plates, K and L, placed under 
the globe, which are turned by the diurnal revolution 
thereof, as by the fame revolution of the earth. Each 
of thefe is divided into twice twelve hours, and parts 
of an hour, to anfwer for the hours of the day ; on the out- 
fide are laid down the degrees of longitude for every 
hour ; fo that thefe circles give at fight the hour of the 
day or night, at any two places on the globe, with the 
difference of longitude correfponding thereto. There 
is alfo a further improvement added to this conftruftion, 
which renders it a planetary globe ; for, by fetting the 
pillar, fig. 4, to the place of any planet in the ecliptic, 
and the ball to the latitude of the planet, it will folve 
all problems relative to that planet, or to the moon; 
as it does likewife for the fun, by means of a central 
folar ray. 
Toretiify this globe, fet the divifion under the repre- 
fe.ntative inhabitant over the given place, fet the folar 
index, L, to the day of the month ; then turn the globe 
round on the axis till the meridian coincides with the 
central folar ray, and the hour index under the globe 
to XII; and this globe is then in the true pofition of 
the eartli, with refpetl to tlic fun and that given place. 
If the inhabitant be placed on tlie wellern fide of ths 
terminator, he will fee the fun, or the central folar ray, 
rifing in the horizon; and this ray vdll mark thereon 
the fun’s amplitude, while the iiour circle gives the 
hour and minute of the fun’s rifing on that day and 
place. Turn the globe gradually till the meridian coin¬ 
cides with the central folar ray, and the point will mark 
out the fun’s meridian altitude for that day. As the 
globe goes on, the altitude decreafes, and when the in¬ 
habitant is arrived at the other fide of the terminator, 
the folar ray is in the horizon, and points out the fun’s 
amplitude, with the time of his fetting on the hour 
circle. If you proceed to turn the globe till the inha¬ 
bitant is under that circle which is behind the termi¬ 
nator, the hour-circle gives the time that twilight 
finilhes. The liin’s altitude for any given time of the 
day, is obtained by Hopping the globe when the index 
points out that hour, and the quadrant of altitude over 
the inhabitant, and then bringing it to the central ray, 
which will point out thereon the altitude for that hour. 
In this manner may be folved fimilar quefiions for any 
other place, or any other day ; always obferving, 1. To- 
fix the inhabitant over the given place. 1. To fet the 
fun’s annual index to the given day of -the month. 
3. To bring the meridian to the central folar ray, and 
the hour index under the globe toXII. By placing the 
fmall pillar, fig. 4, to the moon’s place in the ecliptic',, 
and the ball to her latitude, the fame problems may be 
Iblved at the fame time for the moon; and fo refpec- 
tively of any other planet. Hence, by this globe, a. 
perfon entirely unacquainted with aftrononiy may, in a- 
lew days, acquire a competent and natural notion of 
the principal phenomena, and be enabled to folve the 
greatefi: part of the mofi; interelling problems concern¬ 
ing the hin, moon, and planets. 
The celejlial globe is reprefented at fig. 3, in the fame 
engraving. As the terreftrial globe is mounted to cor- 
relpond exadtly with our earth, and every problem an- 
fwered as they are really occafioned by the annual and 
diurnal motion of the earth ; I'o the celeflial globe, to 
be conformable to nature, fhould be as nearly as polfible 
an exadf imitation of the heavens, and their fituation 
with refpett to the earth ; which is far from being the. 
Cafe with the common globes. To make the celeftial 
globe thus conformable to nature, it fhould have no 
motion; the appearance of motion in the firmament, 
arifes. entirely from the diurnal motion of the earth ; 
it is plain, therefore, that whatfoever gives a true re- 
prefentation of the heavens, will have no motion. This, 
celeftial globe is theiefore fixed on an axis, making,, 
like that of the terreftrial globe, 66J degrees with the 
pJane of the ecliptic ; and the ecliptic on this globe 
exactly coincides with the fun’s apparent path round 
the earth. Ail problems concerning the fun, moon,, 
and planets, are performed by the terreftrial globe. 
This celeftial globe needs only to be ufed for the (tars ■ 
and one or two problems will give a fufficient idea of 
the manner of folving all that relates to the ftars. 
To find the latitude and longitude of a given far. —Firft 
find the liar on the globe, and then place tlie index and 
clip, marked A, on the ecliptic plate. Hide the fideriaL 
index till it is exattly over the ftar, and the latitude is 
(hewn on the arc, and the longitude, by the index, on 
the ecliptic. 
To find the rifing, fetting, amplitude, and meridian altitude^ 
of the fame far. — 1 ake the clip from the celeftial globe, 
and put it to the (ame degree of longitude on the ter¬ 
reftrial ecliptic plate ; turn the globe on its axis, and 
the 6ime of its rifing and letting is immediately pointed 
out by the hour index ; its amplitude is fliewn on the 
horizon; its meridian altitude, by the meridian; and 
its azimuth and altitude for any hour, by applying the 
quadrant of altitude under the fiderial index for that 
hour. 
With regard to the utility or difference between thefe. 
improved 
