10 INTRODUCTION. 



the poles. This circle, therefore, must divide the earth into two 

 equal parts, and on this account was called the Equator or Equaller. 

 It was also called the Equinoctial Line, because the sun, when 

 moving in it, makes the days and nights of equal length all over 

 the world. Having also observed, that from the 21st of June to 

 the 22d of December the sun advanced every day towards a cer- 

 tain point, and, having arrived there, returned towards that from 

 which he had set out, from the 22d of December to the 21st of 

 June, they fixed these points, which they called Solstices, because 

 the direct motion of the sun was stopped at them ; and represented 

 the bounds of the sun's motion by two circles, which they named 

 Tropics, because the sun no sooner arrived there, than he turned 

 back. Astronomers, observing the motion of the sun, found its 

 quantity at a mean rate, to be nearly a degree (or the 360th part) 

 of a great circle in the heavens, every twenty-four hours. This 

 great circle is called the Ecliptic, and it passes through certain 

 constellations, distinguished by the names of animals, in a zone or 

 belt, called the Zodiac, within which the moon and all the planets 

 are constantly found. It touches the tropic of Cancer on one side, 

 and that of Capricorn on the other, and cuts the equator obliquely, 

 at an angle of twenty-three degrees twenty-nine minutes, the sun's 

 greatest declination. To express this motion, they supposed two' 

 points in the heavens, equally distant from and parallel to this circle, 

 which they called the Poles of the zodiac, which turning with the 

 heavens, by means of their axis, describe the two fiolar circles. In 

 the artificial sphere, the equinoctial, the two tropics, and two po- 

 lar circles, are cut at right angles by two other circles called 

 Colures, which serve to mark the points of the solstices, equinoxes, 

 and poles of the zodiac. The ancients also observed that, when 

 the sun was in any point of his course all the people inhabiting 

 directly north and south, as far as the poles, have noon at the same 

 time. This gave occasion to imagine a circle passing through the 

 poles of the world, which they called a Meridian and which is 

 immovable in the artificial sphere, as well as the Horizon, which is 

 another circle representing the bounds betwixt the two hemis- 

 pheres, or haif spheres, viz. that which is above and that which is 

 below it. 



DESCRIPTION AND USE OF THE TERRESTRIAL GLOBE. 



The Terrestrial Gloee is a representation of the surface of the 

 earth, on an artificial globe or ball on which the several countries 

 and places are laid down according to their relative situations, and 

 to which the circles~of the sphere before described are transferred. 



Axis and poles of the e AitTH....The axis of the earth is that 

 imaginary line passing through its centre, on which it is supposed 

 to turn round once in twenty-four hours. The extreme points of 

 this line are called the Poles of the earth, one in the north and the 

 other in the south, which are exactly under the two points of the 

 heavens called the North and South Poles. 



Circles of the globe. ...These are commonly divided into the 

 greater and: less. A great circle is that whose plane passes through 

 the centre of the earthj and divides it into two equal parts or hemis-* 



