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the declivity of land, towards the north or south. Clouds 

 also sometimes reflect heat, and watef clouds cool the 

 air. South or south west winds, if without rain, increase 

 warmth ; east or northerly winds occasion cold. When- 

 ever smooth water reflects the sun's rays, it much in- 

 creases heat. And indeed all smooth bodies which re- 

 flect light, reflect heat along with it, and that more or 

 less, according to the closeness of the pores, and the ex- 

 tent, convexity, or concavity of their surface. 



All parts of the earth enjoy nearly the same quantity 

 of the sun's presence in the same space of a year. And 

 yet how widely different is the quantity of heat in some, 

 from that in others ? But it is not, as any one would 

 imagine greatest under the line. This is prevented by 

 the swiftness of his motion. For the nearer he ap- 

 proaches to it, the swifter is his motion from east to 

 west, from north to south, and from south to north. He 

 passes seven degrees, from three and a half south lati- 

 tude, to three and a half north, in eighteen days: where- 

 as at twenty degrees north latitude, he spends a whole 

 month in going three degrees and a hair', and another 

 in returning : so that he is as near the tropic for sixty- 

 seven days, as he was to the line for eighteen. And 

 hence the heat is considerably greater under the tropic, 

 than it is under the line. 



5. The moon moves round the earth in about twenty- 

 eight days, and with the earth round the sun in a year. 

 Yet it always turns nearly the same side to the earth, 

 whence we always observe the same inequalities in its 

 surface. It does not appear that she moves at all 

 round her own axis. None now doubts of the moon's 

 being an opake body : and the spots and unevenesses, 

 which constantly appear upon it, have been judged by 

 some to be valiies, mountains, lakes, and seas. 



Her days and months are of an equal length, which 

 we do not observe of any other body in the heavens. 

 That her day is equal to her month, appears hence. 

 Since in whatever part of her orbit she is, the same 



