82 The Earth considered as a Planet. 



miles nearer to the sun in December than 

 it is in June, and yet in June it is the 

 middle of summer, and in December the 

 depth of winter, which seems a paradox. 

 To obviate this apparent contradiction* 

 it may be observed that the eccentricity 

 of the earth's orbit bears no greater pro- 

 portion to the earth's mean distance from 

 the sun than about 1 to 60, and therefore 

 this small difference of distance cannot 

 occasion any great variation in the heat 

 and cold of the different seasons. But 

 the principal cause of this difference is, 

 that in winter the sun's rays fall so ob- 

 liquely upon us, that any given number 

 of them is spread over a much greater 

 portion of the earth's surface where we 

 live ; and therefore each point must then 

 have fewer rays than in summer.- 

 Moreover, there comes a greater degree 

 of cold in the long winter nights, than 

 there can return of heat in so short days ; 

 1 on both these accounts the cold must 

 increase. But in summer the sun's rays 

 fall more perpendicularly upon us, and 

 therefore com* with greater force, and in 

 greater numbers i>.. the same place ; and 

 by their kr.ig continuance, a much great- 



