HISTORY OF CALIFORNIA. 



139 



wild oats, which, in the valleys, grow most luxuriantly. 

 These grasses and oats mature and ripen early in the 

 dry season, and soon cease to protect' the soil from 

 the scorching rays of the sun. As the summer ad 

 vances, the moisture in the atmosphere and the earth, 

 to a considerable depth, soon becomes exhausted ; 

 and the radiation of heat, from the extensive naked 

 plains and hill-sides, is very great. 



" The cold, dry currents of air from the north-east, 

 after passing the Rocky Mountains and the Sierra 

 Nevada, descend to the Pacific, and absorb the moist 

 ure of the atmosphere, to a great distance from the 

 land. The cold air from the mountains, and that 

 which accompanies the great ocean current from the 

 north-west, thus become united ; and vast banks of 

 fog are generated, which, when driven by the wind, 

 has a penetrating, or cutting, effect on the human 

 skin, much more uncomfortable than would be felt in 

 the humid atmosphere of the Atlantic, at a much 

 lower temperature. 



" As the sun rises from day to day, week after week, 

 and month after month, in unclouded brightness dur 

 ing the dry season, and pours down its unbroken rays 

 on the dry, unprotected surface of the country, the 

 heat becomes so much greater inland than it is on the 

 ocean, that an under-current of cold air, bringing the 

 fog with it, rushes over the coast range of hills, and 

 through their numerous passes, towards the interior. 



"Every day, as the heat, inland, attains a sufficient 

 temperature, the cold, dry wind from the ocean com 

 mences to blow. This is usually from eleven to one 

 o'clock ; and, as the day advances, the wind increases 

 and continues to blow till late at night. When the 

 vacuum is filled, or the equilibrium of the atmosphere 



