The Earth considered as a Planet. 75 



poles towards the sun, that occasions the 

 very long days in the northern and south- 

 ern parts. It is owing to the same cause, 

 that the sun seems to rise higher in the 

 heavens during summer than in winter ; 

 and this alternate sinking and rising is 

 perceptible over the whole globe. 



In order to illustrate this subject let 

 us now take a view of the earth in its an- 

 nual course round the sun, considering' 

 its orbit as having no inclination | and 

 its axis as inclining 23 -| degrees from 

 a line perpendicular to the plane of its 

 orbit, and keeping the same oblique di- 

 rection in all parts of its annual course ; 

 or, as commonly termed, keeping always 

 parallel to itself. 



In Fig. 2 let S represent the sun, the 

 four globes the earth in different parts of 

 its orbit, receiving from its changing po- 

 sition the varying seasons. Ns its axis, 

 N its north pole, s its south pole. As it 

 goes round the sun, according to the order 

 of the signs of the zodiac, its axis Ns 

 keeps the same obliquity, and is still par- 

 allel to itself. 



We shall commence its annual round at 

 the first point of Libra, when the sun, as 



