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day is- protracted throughout the whole globe, and the 

 long and dismal nights are shortened in the frigid zones. 

 Yea, the sun rises in appearance, when he is indeed 

 many degrees below the horizon* 



Let us a little more attentively consider the light" 

 \vhich whitens the sky before the sun rises. There is 

 something surprising in this. We see the light only by 

 the rays which flow to our eyes. Now the sun being as> 

 yet beneath the earth, cannot project any of his rays 

 directly to us. And the rays which dart on the extre- 

 mities of the land that terminates our sigJjt, proceed 

 farther into the heavens, unless they meet with- any body 

 which reflects them back to us. Is there any particular 

 body in nature designed to do us this service ? There is, 

 namely, the atmosphere, which is framed over our heads- 

 in such a manner, that notwithstanding its extensive 

 mass, it suffers us to see the stars, at an immense distance, 

 from us ; and notwithstanding its transparency, bends- 

 and gathers for us numberless rays, of which, we should, 

 otherwise be quite deprived. 



Any ray that falls perpendicularly on the atmosphere, 

 enters it -without any obstacle, and descends through it 

 to the earth in the same right line. But those which 

 fall obliquely upon it, are admitted into, or repelled from 

 it, according to the situation of the luminous body. If 

 this he more than eighteen degrees below the horizon, 

 all its rays are scattered abroad. If less, the rays enter 

 the atmosphere, and are retracted to our sight. This is 

 the true cause of the twilight, and indeed of the conti- 

 nuance and principal beauty of the day, even when the 

 sun is in its highest elevation. The earth which receives 

 his rays reflects them into the atmosphere, which once 

 more returns the greater part of them. Thus it preserves 

 to us that splendour which is the beauty of nature, and 

 that heat which is the soul of it. For it collects num* 

 berless rays, the greater or smaller union whereof, is the 

 measure of L**t aud cold. Thus it becomes to us a 



