454 Moyfoons tr [Book V. 



motion of the earth, and that the difference between 

 the heat of the day and the night is almoft all that is 

 perceived in thole tropical regions j whereas in the 

 polar regions the great vipifiitudes of heat and cold 

 are occafioned by the annual motion of the globe, 

 which produces the fenfible changes of winter andfum- 

 tner j confequently, if the heat of the fun was the only 

 caufe of the variation of the winds, the changes, if 

 any, that would be produced by thofe means in equa- 

 torial regions, ought to be diurnal only, but the changes 

 about the pole fhould be experienced only once in fix 

 rnonths. As the effecls arifing from tV> heat of the 

 fun upon the air muft be greater at the equator than at 

 the poles, 1 the changes of the wind arifing from the ex- 

 panfion of the air by the fun's rays muft be more fteady 

 in equatorial than in polar regions. The incontrover- 

 tible evidence of navigators proves this truth, that 

 winds are more variable towards the poles, and more 

 conftant towards the equator. But in fummer, the 

 continual heat, even in high latitudes, comes to be fen- 

 fibly felt, and produces changes on the wind, which are 

 diftinctly perceptible. In our own cold region, the 

 effects of the fqn on the wind are felt during the fum- 

 mer months ; for while the weather in that feafon of 

 the year is fine, the wind generally becomes ftronger as 

 the time of the day advances, and dies away towards the 

 evening, and affumes that pleafing fcrenity fo delight- 

 ful to our feelings. Such are the diurnal changes of 

 the wind in northern climates. The annual revolution 

 of the fun produces ftill more fenfible effects. The 

 prevalence of the weftern winds during fummcr 4 we may 

 attribure to this caufe, -which is ftill more perceptible 

 in France and Spain j becaufe the continent of land to 

 the eaftward, being heated more than the waters of the 

 Atlantic Ocean, the air is drawn, during that feafon, 



towards 



