22 



INTRODUCTION. 



Capricorn, he is not visible for the same distance round the Arctic pole. Circles drawn round 

 the poles at that distance, are called respectively the Jlrctic and Antarctic circle. 



8. Zones. These circles and the tropics divide the surface of the earth into five bands or 

 zones ; that which lies between the tropics, on both sides of the equator is called the torrid 

 zone ; the band between the tropic of Cancer and the Arctic circle, is called the northern tem- 

 perate zone, and that included within the Arctic circle the northern frigid zone. Between the 

 tropic of Capricorn and the Antarctic circle, is the southern temperate zone, and within the 

 Antarctic circle, the southern Jrigid zone. 



9. Dimensions and Divisions of the Earth. The mean diameter of the earth is 7,912 

 miles ; its circumference at the equator nearly 24,900 miles ; and its area 198 million square 

 miles. The surface is divided into land and water ; the foamer occupies about 50 million square 

 miles, and the latter 148 millions, being nearly three fourths of the whole surface. 



10. Representation oj the Earth. In order to obtain a correct conception of the appearance 

 of the surface of the earth, representations of that surface, on a small scale, ought to be pre- 

 sented to the eye. TJiere are two ways in which the earth may be thus represented to our 

 view ; viz. by globes and by maps. 



1 1 . Globes. The appearance of the surface of tlie earth may be delineated upon the sur- 



face of a solid having the same figure as the earth. 

 This is the most accurate mode of representation, 

 for an exact image of it may in this way be form- 

 ed. Such an image of the earth is called a ter- 

 restrial globe. 



12. Afaps. The other way of representing the 

 earth's surface, is by drawing a part of it upon a 

 plane. Such drawings are called maps. The 

 necessity of maps arises from large globes being 

 very expensive and inconvenient for use ; while 

 on small ones sulFicient details cannot be intro- 

 duced. 



Maps are constructed by making a projection of 

 the globe, on the plane of some particular circle, 

 supposing the eye placed at some particular point, according to the rules of perspective. 



In maps three things are required ; First to show the latitude and longitude of places, which 

 IS done by drawing a certain number of meridians and parallels of latitude ; Secondly, the 

 shape of the countries must be exhibited as accurately as possible ; for real accuracy cannot 

 oe obtained by projection, because the n^ap is on a plane surface, whereas the earth is globu- 

 •ar ; Thirdly, the bearings of places, and their distances from each other must be shown. 



In all maps, the upper part is the north, the lower the south, the right the east, and the left 

 he west. On the right and left the degrees of latitude are marked. 



III. LAND AND WATER. 



1. Continents. The land surface of the earth is divided into three vast masses called con- 

 Mients, and numerous smaller tracts, called islands. The eastern continent comprises three 

 great divisions called Asia, Europe, and Africa, lying chiefly upon the north of the equator ; the 

 western continent comprises two divisions called North America and South America ; and the 

 southern continent or New Holland lies to the south of the equator. The eastern continent 

 has an area of 31,500,000 square miles; the western of 14,800,000; and the southern of 

 4,200,000. 



2. Islands. Smaller portions of land scattered over the ocean, or otherwise surrounded by 

 water, are called islands ; some of these form considerable masses, as Borneo and Madagascar, 

 the largest known islands. A number of islands lying near each other is called a group or 

 cluster ; several groups lying near each other are often called an archipelago. Small islands 

 are also called islets ; keys are rocky islets, which are sometimes numerous along the coasts 

 of continents or lar2,e islands. 



