RED FOGS AND SEA BREEZES. 141 



from the pure snows of the Andes. Between this range and the 

 coast, instead of marshes and a jungle, there is a desert — a rain- 

 less country, upon which the rays of the sun play with sufficient 

 force not only to counteract the trade-wind power and produce a 

 calm, but to turn the scale, and draw the air back from the sea, 

 and so cause the sea breeze to blow regularly. 



318. Influences which regulate their strength. — On the coast of 

 xVfrica, on the contrary, a rank vegetable growth screens the soil 

 from the scorching rays of the sun, and the rarefaction is not 

 every day sufficient to do more than counteract the trade-wind 

 force and produce a calm. The same intensity of ray, however, 

 playing upon the intertropical vegetation of a lee-shore, is so 

 much force added to the sea breeze ; and hence, in Brazil, the 

 sea breeze is fresh, and strong, and healthful ; the land breeze 

 feeble, and therefore not so sickly. Thus we perceive that 

 the strength as well as regularity of the land and sea breezes 

 not only depend upon the topography of a place, but also upon 

 its situation with regard to the prevailing winds ; and also that 

 a given difference of temperature between land and water, though 

 it may be sufficient to produce the phenomena of land and sea 

 breezes at one place, will not be adequate to the same effect at 

 another ; and the reason is perfectl}^ philosophical. 



319. Land breezes from the west coast of Africa scorching hot. — It 

 is easier to obstruct and turn back the current in a sluggish than 

 in a rapid stream. So, also, in turning a current of air first 

 2ipon the land, then upon the sea — very slight alternations of 

 temperature would suffice for this on those coasts where calms 

 would prevail were it not for the land and sea breezes, as. for 

 instance, in and about the region of equatorial calms ; there the 

 air is in a state of rest, and will obey the slightest call in any 

 direction ; not so in regions where the trades blow over the land, 

 and are strong. It requires, under such circumstances, a con- 

 siderable degree of rarefaction to check them and produce a 

 calm, and a still farther rarefaction to turn them back, and convert 

 them into a regular sea breeze. Hence the scorching land breeze 

 (§ 317) on the west coast of Africa : the heat there may not have 

 been intense enough to produce the degree of rarefaction required 

 to check and turn back the south-east trades. In that part of the 

 w^orld, their natural course is from the land to the sea, and there- 

 fore, if this view be correct, the sea breeze should be more feeble 

 than the land breeze, neither should it last so long. 



