92 THE PHYSICAL GEOGRAPHY OF THE SEA. 



a rainy and dry season in California, another at Panama, two at 

 Bogota, none in Peru, and one in Chili. 



189. In Oregon it rains every month, but about five times more 

 in the winter than in the summer months. 



The winter there is the summer of the southern hemisphere, 

 when this steam-engine (§ 168) is working with the greatest press- 

 ure. The vapor that is taken up by the southeast trades is borne 

 alono' over the region of northeast trades to latitude 35° or 40° 

 north, where it descends and appears on the surface with the 

 southwest winds of those latitudes. Driving upon the highlands 

 of the continent, this vapor is condensed and precipitated, during 

 this part of the year, almost in constant showers, and to the depth 

 of about thirty inches in three months. 



190. In the winter, the calm belt of Cancer approaches the 

 equator. This whole system of zones, viz., of trades, calms, and 

 westerly winds, follows the sun ; and they of our hemisphere are 

 nearer the equator in the winter and spring months than at any 

 other season. 



191. The southwest winds commence at this season to prevail 

 as far down as the lower part of California. In winter and spring, 

 the land in California is cooler than the sea air, and is quite cold 

 enough to extract moisture from it. But in summer and autumn 

 the land is the warmer, and can not condense the vapors of water 

 held by the air. So the same cause which made it rain in Ore- 

 gon now makes it rain in California. As the sun returns to the 

 north, he brings the calm belt of Cancer and the northeast trades 

 along with him ; and now, at places where, six months before, the 

 southwest winds were the prevailing winds, the northeast trades 

 are found to blow. This is the case in the latitude of California. 

 The prevailing winds, then, instead of going from a warmer to a 

 cooler climate, as before, are going the opposite way. Conse- 

 quently, if, under these circumstances, they have the moisture in 

 them to make rains of, they can not precipitate it. 



192. Proof, if proof were wanting that the prevailing winds in 

 the latitude of California are from the westward, is obvious to all 

 who cross the Eocky ]\Iountains or ascend the Sierra ]\Iadre. In 

 the pass south of the Great Salt Lake basin those west winds 



