356* GEOGRAPHY. 
bring' any part of its furface under tliis circle, which 
will then reprefent the meridian of any given place.— 
One fide of this circle is divided into four quadrants, 
each confifting of ninety degrees. The numbers on two 
of thefe quadrants commence from the equator, and 
proceed each way to the north and fouth pole ; the 
numbers on the other two quadrants increafe from the 
pole towards the equator. The numbers which pro¬ 
ceed from the equator point out the difiance of the ze¬ 
nith of any place from the equator, which is its latitude. 
And the latitude is north or fouth, according as the places 
are on the north or fouth fide of the equator. The de¬ 
grees which are numbered the contrary way from the 
pole, are to fiiew the height or elevation of the pole 
above the horizon. We have before fitewn that the 
elevation of the pole is equal to the latitude of the 
place.—By this circle is alfo meafured the diftance of 
tlie fun or fiar from the equator, which is its declination ; 
and thus, if we bring the highefi or mofi northern part 
of tlie ecliptic to the meridian, it wij_l cut th.e lame in 
23! degrees; and fo much is the declination of that 
point. 
To reciify the fphere, is to put it intlvat pofition in which 
it may rejirelent exaiftly the apparent motion of the 
heavens. For different places tliat pofition mufi be dif¬ 
ferent, according to the dift'erent elevation of the pole, 
or latitude of tlie place. Therefore to redtify the 
Iphere, elevate the pole till the fame number of degrees 
are above the plane of the horizon, as the pole of the 
place you are confidering is above its horizon ; and then 
the circles on tlie fphere will, with refpeT to the globe 
lulpended within it, correfpond tvith the imaginary cir¬ 
cles in the heavens. 
Tlie equator, E Q, is tlie great circle which furrounds 
the fphere exadfly in the middle between the two poles 
ot the worrd ; and the ecliptic, which reprefents the 
fun’s path, cuts this circle in two oppofite points, and 
therefore, as ftated above, the fun is twice a-year in this 
circle ; and as one half of it is always above the hori¬ 
zon, and th.e other half below, when the fun is in thofe 
two points, the days and nights are equal. This circle 
is called the equator, becaule it equates or divides the 
globe of the earth into two equal parts ; it is often alfo 
called the equinoElial, becaufe that when the fun is in this 
circle, the days are equal to the nights. It is divided into 
36odegrees, beginning and endingin the equinoctial point, 
and numbered from weft to eafi; thefe degrees on the 
fphere are called degrees of right afccnfion, but the de¬ 
grees on the equator, as laid dowm on a terreftrial globe, 
are called degrees of longitude, explained above. Hence 
a meridian, palling through the fun, planets, or fiars, 
thews on the equator the degree of its right alcenfion, 
or diftance from the equinoctial point. 
The hour circle, a, is a fmall circle fixed about the 
north pole, with a hand on the axis of the fphere, fo 
that by turning the fphere on its axis, the index v.”!!! be 
carried round the circle. This is tiled to convert tiie 
degrees of the equator into time; it is divided into 
twenty-four equal parts, anfwering to twenty-four hours, 
or the time of an entire revolution of the heavens. 
The index, by pointing fuccellively to thofe hours, 
fiiews in what fpahe of time any part of that revolution 
is performed. Th.e twelve hours are twice engraved on 
thl s circle ; the firfi twelve hours fticw the time from 
noon to midnight, the other from midnight to noon the 
next day. And (ince all aifrenomers begin the day at 
noon, therefore the two hours of tv/elve fiand directly 
upon the graduated edge of the meridian. 
The ecliptic, C D, is to called, becaufe there can be no 
eclipfes of the fun and moon, but when the moon is in 
or near Hiis circle ; for this reprefents the fun’s appa¬ 
rent annual path, and therefore whenever the moon ob- 
feures the-fun, or is oblcured by him, the mufi be in or 
near the ecliptic. It is generally graduated into twelve 
equal parts, confifting of thirty degrees each, the be- 
2 
ginning of the part being marked with characters re-' 
prefenting the twelve figns. Aftronomers divided the 
ecliptic in this manner in order to judge more eafily, 
and exprefs. more clearly, the places of the fun, moon, 
and planets; for it is eafier to obtain an. idea of their 
fituation by referring them to fome part of a known 
figure, than it could poffibly be by merely confidering 
degrees in tlie circumference and expanfe of the hea¬ 
vens. The points where this circle cuts the equator, 
are called the equinoCIial points. It is by the ecliptic 
that we eftimate the latitude and longitude of the hea¬ 
venly bodies. 
The zodiac, HO, is the broad circle in the heavens, 
which contains the twelve figns ; and Is called the zo¬ 
diac, becaufe, according to the Chaldean divifion, it 
confified only of animal figures ; w'hat is now called 
Libra, being by them reckoned a part of Scorpio, and 
making the claws of that animal. The divifion of the 
zodiac into twelve parts correfponds with the divifion 
of the year into twelve months, and anfwers to the apl 
parent motion of the fun, as deferibed above. 
The next circles of the fphere are thofe tw'o called 
the colures, both of which pals through the poles of tlie 
world, and cut the equator at right angles. One of 
thefe palFes through the equinoiSlial points, and is called 
the equinoElial cohire, N ; the other palfes t.hrough the 
folftitial point, P, and is called the jolfiitial colure. 
The two tropics, S and T, are parallels, and diftant 
2'^ degrees from the equator on each fide of it, at which 
diftance they touch the ecliptic in the folftitial points. 
Wiiile the fun is going from Aries to Cancer, he ad¬ 
vances every day more northward, till he comes to 
Cancer, his moft northward fituation ; after which he 
begins to defeend to Libra, getting every day more 
fouthward than before. Now, when he is in the begin¬ 
ning of Cancer, he changes Iris motion, and turns from 
going northward to go fouthward ; this turning back is 
meant by the word tropic, from vvhence the parallel 
pafiing through Cancer is called the tropic of Cancer; and 
for the fame reafon the other is called the tropic of Capri¬ 
corn, becaufe there the fun retuj'ns from the foutherly 
courfe to the northern one. 
The polar circles, V and U, are the imaginary ciicles 
in the heavens,- which correfpond to thofe parts of the 
earth that were termed by the ancients x\\e frigid zones; 
they include 23A degrees on each fide their refpertive 
poles. Thefe circles are by many authors called the 
arElic and antarctic circles, but improperly, as the ancients 
meant by the arctic circle the largeft parallel that was 
always above the horizon of any particular place, con¬ 
taining all thofe ftiirs which never let at that place, but 
feem to be carried round above our horizon in circles 
parallel to the equator. The largeft parallel, v/hich is 
entirely hid below the horizon of any place, they called 
the antarttic circle, or circle of perpetual occultat;ion. 
This includes all the ftars wliich never rife to an in'ia- 
bitant of the northern hemifphere, but are perpetually 
below the horizon. All arctic circles touch their hori¬ 
zons in the north point, and all antarCftic circles touch 
their horizons in the fouth point. Thofe who live un¬ 
der either tropic have one of the polar circles for their 
ariftic, and the other for their antarctic, circle ; thus the 
names of mutable circles have been given to the immu¬ 
table polar circles, which are only ar6t;ic and antarftic 
circles in one particular cafe. 
Of the three fituations of the celeftial fphere, de- 
feribed above, (article 31,) as applicable to the inlia- 
bitants of the earth, we may form a very clear concep¬ 
tion by means of the armillary Iphere. 
The right fphere, or fphere of thofe inhabitants who live 
under the equator ,—To ftiew the jiofition of the circles 
of the fphere with refpeft to thefe inhabitants, bring 
the equator into the zenith', and tlie poles of the \vorld 
lie in the horizon. The equator, the tropics, and polar 
circks; all Hand perpendicular to the horizon ; hea¬ 
venly 
