Half a Globe or Sphere is called a Hemifphere.

The Terreftrial Globe is an artificial Representation of the natural Earth, having the whole Surface of the Land and Sea drawn upon it, in their natural Form, Order, and Situation.

The Spindle on which the Globe turns is called its Axis *; which in the artificial Globe is real, in the natural only imaginary.

The two extreme Points of the Earth's Axis are called its Poles, viz. the North, called the Arctic; and the South, called the Antarctic.

The Earth is fuppofed to be furrounded with several imaginary Circles, which are either drawn upon the artificial Globe, or expreffed by the Wooden and Brass Work about it.

These Circles are diftinguished into Greater, and Leffer. The greater Circles divide the Globe into two equal Parts, the leffer into unequal.

Of the Greater Circles, viz. the Horizon, the Equator, Meridians, and the Ecliptic.

I. The HORIZON, which is expreffed by

*The Reader who defires to know the derivation of the terms of Art made ufe of in this Treatife, is referred to larger fyftems, particularly Gordon's Geographical Grammar, P. 1. § .-Hubner's Introduction to Geography, C. L.-6.

the

the

upper Surface of the wooden Circle in which the Globe ftands, divides the Globe into an upper and lower Hemisphere. This is called the Rational Horizon, to distinguish it from the fenfible or apparent Horizon, which bounds our Profpect all round us, and which is greater or lefs, according as we ftand higher or lower. For Example, an Eye placed at five Feet above the Surface of the Earth or Sea, fees two Miles and three Quarters every way: but if it be at twenty Feet high, it fees five Miles and an half.

The Rifing and Setting of the Sun and Stars properly refpects the Rational Horizon; that is, they rife when they get above it, and fet when they fink below it: But, by reafon of their vaft Distance from us, the Rational and fenfible Horizon are to be confidered, in this Cafe, as one and the fame.

The wooden Horizon of the Globe has feveral Circles drawn upon it. The outermoft is marked with the Points of the Mariners Compafs; of which the East, Weft, North, and South, are called the Cardinal Points, dividing the Horizon into four Quarters. Each of thefe Quarters is fubdivided into eight Points, in all thirtytwo, called Rumbs; and Lines drawn from any Point upon the Surface of the Globe towards the feveral Rumbs, are called B 2

Rumb

Rumb Lines. The other Circles upon the Horizon will be confidered afterwards.

II. The EQUATOR divides the Globe into the Northern and Southern Hemifpheres. This is what Sailors call The Line; and when they pafs over it at Sea, they are faid to cross the Line. From this Line the Degrees of Latitude are counted towards the Poles, viz. 90 towards each Pole *.

III. Semicircles reaching from Pole to Pole, and cutting the Equator at right Angles, are called MERIDIANS. 360 fuch Semicircles, drawn at equal Diftances, quite round the Globe, mark the Degrees of Longitude, which are numbered upon the Equator, and are counted from the firft Meridian.

The Meridian which paffes through Fero, one of the Canary Islands, is gene

Fig. 1.

* Every Circle, whether great or small, is fupposed to be divided into 360 equal Parts called Degrees. Two Lines drawn from any two Points in the Circumference of a Circle to the Center (except two Points that lie in a strait Line with the Center, as A and E) form an Angle at the Center which is called an Angle of fo many Degrees, as are contained in the Arch of the Circle betwixt the two Points. Thus an Angle of go Degrees, or right Angle, is meafured by of the Circle; an Angle of 450 by ACB is an Angle of 969, BCD 45° ACD 135°. N. B. A Degree is divided into 60 Minutes, a Minute into 60 Seconds, a Second into 60 Thirds, &c.

So much as any Angle, or Arch of a Circle, wants of 90 Degrees, is called the Compliment of that Angle or Arch; as DE is the Compliment of the Arch B D, and of the Angle B C D.

rally

rally made the firft Meridian upon the Terreftrial Globe.

But different Nations fix the first Meridian in different Places: Some English Geographers and Map-makers, make that to be the first Meridian which paffes thro' London. And the Longitude is counted from it, East and Weft.

Two of these Semicircles joined together, fo as to compleat the Circle, are called Whole Meridians. Such a one is expreffed by the brazen Circle in which the Globe turns, and by which it is divided into the Eaftern and Western Hemifpheres. The graduated Edge of this Meridian represents the Meridian of any Place, when, by turning the Globe, the Place is brought just under it.

Meridians at fifteen Degrees diftance from each other are called Hour-circles; because the Places that each of them pass through have Noon an Hour earlier than at fifteen Degrees more Westward, and later than at fifteen Degrees more Eaftward. Hence the Longitude is often expreffed by Hours, as Long. W. of London 4ħ 17TM for 64° 15′ West of London.

h

N. B. The Horizon and Meridians are called changeable Circles; because by changing our Place, Eastward or Weftward, we change our Meridian; fince the Meridian of any Place is a Circle paffing, North and

B 3

South,

South, directly over it. And by removing towards any Point of the Compass we change our Horizon, both sensible and Rational; fince both the Profpect all around us, and the Hemisphere which we stand in the Middle of, are now bounded by different Circles than they were before.

The Changeableness of these Circles is represented by the Globes being made to move within them; by which Means any Place can be brought under its proper Meridian and into the Middle of the He; mifphere which is bounded with its proper Horizon.

IV. The ECLIPTIC cuts the Equator obliquely in two oppofite Points, making with it an Angle of twenty-three Degrees and an half. This is that Circle round the Earth, which anfwers to the Sun's apparent annual Path in the Heavens: or it is fuch a Circle on which if you fuppose a Man to travel round the World in the Space of a Year, keeping pace with the Sun's apparent annual Motion, i. e. about fixty-feven Miles a Day, and fuppofe he has the Sun vertical, or directly over his Head, the first day at Noon, he will have the Sun. directly over his Head every day at Noon throughout the Year.

This Circle is divided into twelve times 30 Degrees, in all 360. These twelye Por

tions