APPENDIX. 301 



N is turned towards the sun in June and from it in Dec. ; 

 it is warmer therefore at the former season than at the latter. 

 But to render the subject more plain it may be proper to 

 trace the annual motion of the earth in its orbit. About the 

 20th of March the earth is in Libra, and consequently to its 

 inhabitants the sun will appear in Aries, and be vertical to, 

 or over the equator. The equator and all its parallels are 

 then equally divided between the light and the dark, and 

 consequently the days and nights are equal all over the 

 world. As the earth pursues its journey from March to June, 

 its northern hemisphere comes more into light, and on the 

 21st of that month, the sun is vertical to the tropic ot Can- 

 cer. All the circles parallel to the equator are then unequal- 

 ly divided ; those in the northern half have their greater 

 parts in the light, and those in the southern have their longer 

 parts in darkness ; it is summer therefore to the inhabitants 

 of the northern hemisphere, and winter to the soutijern. 

 Trace the earth now to September, and the sun is found 

 vertical again to the equator, and, of course, the days and 

 nights are again equal. And following the earth in its 

 journey to Decemi)er, or when it has arrived at Cancer, the 

 sun appears in Capricorn ; and it is vertical to that ^.art of 

 the earth called the tropic of Capricorn, and now the southern 

 pole is enlightened, and all the circles in that hemisphere have 

 their longer parts in the light, and, of course, it is summer 

 to those parts, and winter to us in the northern hemiriptiere. 

 Note. Since it is summer to all those parts of the earth, 

 where the sun is vertical, and we find the sun is vertical 

 twice in the year to the equator, and every part of the globe 

 between the equator and tropics, consequently there are two 

 summers in a year to all those places ; and in those parts 

 near the equator, they have two harvests every year. 



LESSON 48. 



Figures 42 and 43. The Tides. S the sun, M the moon, 

 E the earth, represented as covered with water. When the 

 waters at c fig. 42, are under the moon, they will b heaped 

 up at c, and recede from the intermediate points a and &, 

 and being less attracted on the opposite side will be heaped 

 up also at d. The sun tends to raise tides at a and 6, but 

 its only effect is to diminish those of the moon. In fig , 

 26 



