-Chap, ii.] Land and Sea Breezes. 453 



crn tropic, and a fouthern one in the other tropic ;. but 

 as the earth's diurnal motion varies thedireft influence 

 of the fun over the furface of the earth, and as by that 

 motion this influence is communicated from eaft to 

 weft, an eafterly wjnd would be produced, if this in- 

 fluence alone prevailed. On account of the co-optra- 

 tion of thefe two caufes at the fame time, the trade -' 

 winds* blow naturally from the N. E. on the north, and 

 from the S. E. on the fouth of the line, throughout the 

 whole year; but as the fun approaches nearer the'tropic 

 of Cancer in our ftimrner feafon, the point towards 

 which thefe winds are directed will not be invariably 

 the fame, but they will incline more towards the north 

 in that feafon, and more towards the fouth in our 

 winter. 



The Ian4 zndfea breezes in the tropical climates may 

 be confidcred as partial interruptions of the general 

 trade winds, and the caufe of thefe it is not very diffi- 

 cult to explain. From water being a better conductor 

 of heat than earth, the water is always of a more even 

 temperature. During the day, therefore, the land be- 

 comes confiderably heated, the air rarefied, and con-- 

 fequently in the afternoon a breeze lets in from the 

 fea, which is lefs heated at that time than the land. 

 On the other hand, during the night, the earth lofes its 

 furplus heat, while the fea continues more even in its 

 temperature. Towards morning, therefore, a breeze 

 regularly proceeds from the land towards the ocean, 

 where the air is warmer, and confequently more rarefied 

 than on ihore. 



The caufe of the mcnfoons is not (b well underflood 

 as that of the general trade winds j but what has been 

 jufl remarked, fuggefts, at lead, a probable theory 

 on the fubject. It is well known, that at die equator the 

 changes of heat and cold are occafioned by the diurnal 

 Gg 3 motion 



