OF THE HEAVENS AND THE EARTH. 289 



delightful and demonstrative view of the cause of days LECT. 



. VIII & IX. 

 and nights, with their gradual increase and decrease in ^-v~vJ 



length, through the whole year, together with the vicis- 

 situdes of spring, summer, autumn, and winter, in each 

 annual course of the earth round the sun. 7 * 



If the hoop be divided into 12 equal parts, and the 

 signs be marked in order upon it, beginning with Can- 

 cer at the highest point of the hoop, and reckoning east- 

 ward (or contrary to the apparent motion of the sun) 

 you will see how the sun appears to change his place 

 every day in the ecliptic, as the globe advances east- 

 ward along the hoop, and turns round its own axis : 

 and that when the earth is in a low sign, as at Capricorn, 

 the sun must appear in a high sign, as at Cancer, oppo- 

 site to the earth's real place : and that whilst the earth is 

 in the southern half of the ecliptic, the sun appears in the 

 northern half, and vice versa: that the farther any place 

 is from the equator, between it and the polar circle, the 

 greater is the difference between the longest and short- 

 est day at that place , and that the poles have but one 

 day and one night in the whole year. 



These things premised, we shall proceed to the de- 

 scription and use of the terrestrial globe, and explain 

 the geographical terms as they occur in the problems. 



This globe has the boundaries of land and water laid The terres- 

 down upon it, the countries and kingdoms divided by descried! 

 dots, and coloured to distinguish them, the islands pro- 

 perly situated, the rivers and principal towns inserted, 

 as they have been ascertained upon the earth by mea- 

 surement and observation. 



The equator, ecliptic, tropics, polar circles, and 



ATote 75. Mr. Christie has contrived an improved apparatus, operating 

 on nearly similar principles, and it is but justice to the above ingeni- 

 ous mathematical Professor to add, that his tellurian appears admi- 

 rably adapted for the purpose of explaining most of the problems de- 

 scribed by oar An.thor. 



19. u 



