24 THE YEAR. 



quadrant or quarter of the orbit is passed over, the 

 angular difference will be reduced to nothing, and there 

 will be an equal continuance of solar light throughout 

 the whole globe, only its intensity will diminish toward 

 the poles till at both it be merely the illumination of a 

 sun in the horizon, as when that luminary is rising or 

 setting. 



After this the angular distance will again begin, but 

 its influence upon the poles will be reversed, that which 

 was formerly illuminated will be dark, and that which 

 was dark, illuminated. This reversed angular difference 

 will go on increasing during the time that the earth is 

 passing over another quarter, or quadrant ; and when 

 the other extremity of the largest diameter is arrived at, 

 it will be at its maximum ; and the distribution of solar 

 light will be the same as at the beginning, only it will 

 be on the opposite hemisphere, or half, of the earth. 

 For a third quarter, the angular difference will dimi- 

 nish ; at the end of that quarter it will vanish; and 

 through the fourth quarter, which completes the revo- 

 lution of the year, the opposite difference will increase, 

 till at the end of the revolution it will be the same as at 

 the beginning. 



Thus are the light and heat of the sun distributed in 

 the course of the year, in such a manner as to give to 

 each hemisphere alternately the repose of winter and 

 the activity of summer, to prevent any very great 

 length of day in those tropical regions, where a succes- 

 sion of the shade of night is required at short intervals 

 to preserve plants and animals from being destroyed 

 by excessive heat, to accumulate the warmth of the 



