GEOGRAPHY. 
meat of latitude is the difference between 
the latitude itself and 90°, or as much as the 
place itself is distant from the pole; and this 
complement is always equal to the elevation 
of the equator above the horizon ot the place. 
The elevation of the pole ot any place is equal 
to the latitude itself. 
An inhabitant of the earth who lived (if 
it was possible) at either of the poles would 
have always one of the celestial poles in his 
zenith, and the other in his nadir, the equator 
coinciding w ith the horizon. Hence all the 
celestial parallels are also parallel to the ho- 
rizon; w' hence the person is said to live in a 
parallel sphere, or to have a parallel horizon. 
Those who live under the equator have 
both poles in the horizon, all the celestial 
parallels cutting the horizon at right angles; 
whence they are. said to live in a right sphere, i 
or to have a right horizon. ] 
Lastlv, those who live between either of 
the poles and the equator, are said to live in 
an oblique sphere, or to have an oblique ho- 
rizon, because the-celestial equatoi cuts their 
horizon obliquely, and all the parallels in the 
celestial sphere “have their planes oblique to 
that of the horizon. In this sphere some ot 
the parallels intersect the horizon at oblique 
angles, some are entirely above it, and some 
entirely below it; all of them, however, so 
situated, that they would obliquely intersect 
the plane of the horizon extended. 
The largest parallel which appears entire 
above theliorizon of any place in north lati- 
tude is called bv the antient astronomers the 
arctic circle of that place; within this circle, 
that is, between it and the arctic pole, are 
comprehended all the stars which, never set 
in that place, but are carried perpetually 
round the horizon in circles parallel, to the 
equator. The largest parallel which is hid 
entirelv below the horizon of any place in 
north latitude was called the antarctic circle 
of that place by the antients. ihis c.rcie 
comprehends all the stars which never rise 
in that place, but are carried perpetually 
round be. ow the horizon in circles parallel to 
tire equator. In a parallel sphere, however, 
the equator may Ire considered as both arctic 
„ and antarctic circle; for, being coincident: 
with the. horizon, all the parallels on one side 
are entirely above it, anil those on the other 
entirely below it. In an oblique sphere, the 
nearer any place is to either of the poles, the 
larger are the arctic arid antarctic circles, as 
being nearer to the celestial equator, which 
is a great circle. In alright sphere, the arctic 
and antarctic circles have no place, because no 
parallel appears either entirely above or be- 
low it. By the arctic and antarctic circles, 
however, modern geographers in general un- 
derstand two lixed circles at the distance ot 
2 3 ,i degrees from the pole. These are sup- 
posed to be described by the poles ot the 
ecliptic, and mark out the space all round 
the globe where the sun appears to touch 
the horizon at midnight in the summer time, 
and to be entirely sunk below it in the v inter. 
These are also called the polar circles. 
According to the different positions of the 
globe with regard to the sun, the celestial 
bodies will exhibit different phenomena to 
the inhabitants. Thus, in a parallel sphere, 
they will appear 1o move in circles round the 
horizon; in a right sphere they would appear 
to rise and set as at present, but always in 
circles, cutting the horizon at right angles ; but 
in an oblique sphere the angle varies accord- 
ing to the degree of obliquity, and the posi- , 
lion of the axis of the sphere with regard to j 
the sun. Hence we easily perceive the rea- 
son of the sun’s continual change ot place in 
the heavens; but though it is certain that this 
change takes place every moment, the vast 
distance of the luminary renders it impercep- 
tible for some time, unless to very nice astro- 
nomical observers. Hence we may generally 
suppose the place of the sun to be the same 
for a day or two together, though in a con- 
siderable number of days it becomes exceed- 
ingly obvious to every body. When he 
appears in (lie celestial equator, his motion 
appears for some time to be in the plane ol 
that circle, though it is certain that his place 
there is onlv for a single moment ; and in like 
manner, when he comes to any other point 
of the heavens, his apparent diurnal motion 
is in a parallel drawn throughout. Twice a 
vear he is in the equator, and tlieu the davs 
and nights are nearlv equal all over the earth. 
Phis happens in the months ot March and 
September; after which the sun proceeding 
either northward of south, according to the 
season of the year and the position of the ob- 
server, the days become longer or shorter 
than the nights/and summer or winter comes 
on, as is fully explained under the article As- 
tronomy. The secession ot the sun from 
the equator either northward or southward is 
called his declination, and is either north or 
south according to the season of the year; 
and when this declination is at its greatest 
height, he is then said to be in the tropic, be- 
came he begins to turn back (the word tro- 
pic being derived from the Greek rptra, ver- 
to). The space between the two tropics, 
called the torrid zone, extends for no less 
than 47 degrees of latitude all round the 
globe; and throughout the whole of that 
space the sun is vertical to some of the inha- 
bitants twice a year, but to those who live di- 
rectly under the. tropics only once. r l hrough- 
out the whole torrid zone also there is little 
difference between the length ol the days and 
nights. The anticnt geographers found them- 
selves considerably embarrassed in their at- 
tempts lo lix the northern tropic; for though 
they took a very proper method, namely, to 
observe the most northerly place where ob- 
jects had no shadow on a certain day, yet 
they found (hat on the same day no shadow 
was cast for a space of no less than 300 stadia. 
The reason ot this was, tke apparent dia- 
meter o’f the sun, which, being about halt a 
degree, seemed to extend himself over as 
much of the surface of the earth, and to be 
vertical every w here within that space. 
When the sun is in or near the equator, 
he seems to change his place in the heavens 
most rapidly; so that about the equinoxes 
one may very easily perceive the diifeience 
in a day or two; but as he approaches the 
tropics,’ this apparent change becomes gra- 
dually slower, so that for a number of days lie 
scarcely seems to move at all. I he reason 
of this may easily lie understood from any 
map on which the ecliptic is delineated; tqi 
by drawing lines through every degree of it 
parallel to the equator, we shall perceive 
them gradually approach nearer and nearer 
each other, until at last, when we approach 
the point of contact betwixt the ecliptic and 
tropic, they can for several degrees scarcely 
be distinguished at all. 
5 N 2 
635 
From an observation of the diversity in 
the length oi the days and nights, the rising 
and setting o', the sun, with the other pheno- 
mena already mentioned, the antient geogra- 
phers divided l lie surface of the eat tn into 
certain districts, which they calico climates , 
and instead of the method of describing the 
situation of places by their latitude and lon- 
gitude as we do now, they contented them- 
selves with mentioning the climate in which 
they h ere situated. 
This method of dividing the surface of the 
earth into climates, though now very much 
disused, has been adopted by several modern 
geographers. Some ot these begin their cli- 
mates at the equator, reckoning them by the 
increase of half an hour in the length of the 
day northward. I bus they go on till they 
come to the polar circles, where tire longest 
day is 24 hours: betwixt these and the poles 
they count the climates by the increase of a 
natural dav in the length ot time that the sun 
continues above theliorizon, until they come 
to one where the longest day is 15 of ours, or 
half a month ; and from this to the pole they 
count by the increase of half-monlhs or whole 
months, “the climates ending at the poles where 
the days are six months long. 1 he climates 
betwixt the equator and the polar circles are 
called hour-climates, and tuose between the 
polar circles and the poles are called month- 
climates. In common language, however, 
we take the word climate in a very different 
sense; so that when two countries are said to 
be in different climates, we understand only 
that the. temperature of the air, seasons, &c.. 
are different. 
From the difference in the length and posi- 
tions of the shadows of terrestrial substances, 
antient geographers have given different 
terms to the inhabitants of certain places of 
the earth ; the reason of which will be easily 
understood from the following considerations: 
1. Since the sun in his apparent annual revo- 
lution never removes farther f rom the equator 
than 23-- degrees, it follows, that none of 
those who live without that space, or beyond 
the tropics, can have the luminary vertical to 
them at any season ot the year. 2. All who 
live between the tropics have the sun ver- 
tical twice a vear, though not all at the same 
time. '1'hus, to those who live directly undei 
the equator, he is directly vertical in March 
and September at the time of the equinox. 
If a place is in 10° north latitude, the sun is 
vertical when he has 10° north declination, 
and so of every otiier place. 3. All who 
live between the tropics have the sun at 
noon sometimes north and sometimes south 
of them. Ihus those who live in a place 
situated in 20° north latitude have the sun at 
noon to the northward when he has more 
than 20 degrees north declination, and to the 
southward when he has less. 4. Such of the 
inhabitants of the earth as live without the 
tropics, if in the northern hemisphere, have 
the sun at noon to the southward of them, but 
to the northward if in the southern hemi- 
sphere. — 1. Hence when the sun is in the ze- 
nith of anv place, the .shadow of a man or any 
upright object falls directly upon the place 
where they stand, and consequently -is invi- 
sible; whence the inhabitants of such places 
were called Ascii, or without shadows. 
2. Those who live between the tropics, and 
have the sun sometimes to the north and 
sometimes to the south of them, have of con- 
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