110 THE PHYSICAL GEOGRAPHY OF THE SEA. 



commence at this season to prevail as far down as the lower part 

 of California. In winter and spring the land in California is cool- 

 er than the sea air, and is quite cold enough to extract moisture 

 from it. But in summer and autamn the land is the warmer, and 

 can not condense the vapors of water held bj the air. So the 

 same cause which made it rain in Oregon 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. Thia 

 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. Consequently, if, under these cir- 

 cumstances, they have the moisture in them to make rains of, they 

 can not precipitate it. Proof, if proof were wanting that the pre- 

 vailing winds in the latitude of California are from the westward, 

 is obvious to all who cross the Eocky Mountains or ascend the 

 Sierra Madre. In the pass south of the Great Salt Lake basin 

 those west winds have worn away the hills and polished the rock 

 by their ceaseless abrasion and the scouring effects of the driving 

 sand. Those who have crossed this pass are astonished at the 

 force of the wind and the marks there exhibited of its geological 

 AGENCIES. Panama is in the region of equatorial calms. This 

 belt of calms travels during the year, back and forth, over about 

 17° of latitude, coming farther north in the summer, where it tar- 

 ries for several months, and then returning so as to reach its ex- 

 treme southern latitude some time in March or April. Where 

 these calms are it is always raining, ^nd the chart'^ shows that 

 they hang over the latitude of Panama from June to November ; 

 consequently, from June to November is the rainy season at Pan- 

 ama. The rest of the year that place is in the region of the north- 

 east trades, which, before they arrive there, have to cross the 

 mountains of the isthmus, on the cool tops of which they deposit 

 their moisture, and leave Panama rainless and pleasant until the 

 sun returns north with the belt of equatorial calms after him. 

 They then push the belt of northeast trades farther to the north, 

 occupy a part of the winter zone, and refresh that part of the 

 earth with summer rains. This belt of calms moves over more 



* Vide Trade-wind Chart (Maury's Wind and Current). 



