Lesson XXKII.] DAYS AND NIGHTS. 215 



daily track, was immerged inio the western ocean, 

 whence, in the course of the Night, he travelled on 

 to the eastern in order to perform his next di- 

 urnal journey : an absurd doctrine, which is now 

 entirely laid aside ; except, indeed, by the most 

 illiterate. 



But as my young readers will readily admit the 

 near approach of the earth to a spherical form, I 

 must endeavour to explain to them the occasion of 

 Day and Night in a more rational manner. On 

 account of the immense distance of the earth from 

 the sun, and the earth's minute size when compared 

 with him, it is evident that the rays of light emitted 

 from that luminary (setting aside the effects of the 

 atmosphere) will fall upon the earth in parallel 

 directions, and will always illuminate a hemisphere 

 of the earth, whilst the other hemisphere remains 

 in darkness. Hence then, so long as any parti- 

 cular place on the earth continues in the darkened 

 hemisphere, it will be night at that place : but, as 

 soon as that place, by the diurnal rotation of the 

 earth from west to east, is brought to the verge 

 of the enlightened hemisphere, then \sDay-lreak; 

 and 



The morn, in russet mantle clad, 



Walks o'er the dew of you high eastern hill. 



SHAKESPEARE. 



When the meridian of that place is, by the 

 rotatory motion, brought directly beneath the sun, 

 it is then Noon there, and at every place in 

 the enlightened part of the same meridian : but 

 in the darkened part of the same meridian it 



is 



