HISTORY OF CALIFORNIA. 137 



the Sierra Nevada, and are, of course, deprived of all 

 the moisture which can be extracted from them by the 

 low temperature of those regions of eternal snow, and 

 consequently no moisture can be precipitated from 

 them, in the form of dew or rain, in a higher tempera- 

 ture than that to which they have been subjected. 

 They, therefore, pass over the hills and plains of 

 California, where the temperature is very high in 

 summer, in a very dry state ; and, so far from being 

 charged with moisture, they absorb, like a sponge, all 

 that the atmosphere and surface of the earth can yield, 

 until both become, apparently, perfectly dry. 



" This process commences, as I have said, when the 

 line of the sun's greatest attraction comes north in 

 summer, bringing with it these vast atmospheric 

 movements, and, on their approach, produce the dry 

 season in California ; which, governed by these laws, 

 continues until some time after the sun repasses the 

 Equator in September, when, about the middle of 

 November, the climate being relieved from these north- 

 east currents of air, the south-west winds set in from 

 the ocean charged with moisture — the rains commence 

 and continue to fall, not constantly, as some persons 

 have represented, but with sufficient frequency to 

 designate the period of their continuance, from about 

 the middle of November until the middle of May, in 

 the latitude of San Francisco, as the ivet season. 



" It follows, as a matter of course, that the dry 



season commences first, and continues longest in the 



southern portions of the territory, and that the climate 



of the northern part is influenced in a much less 



degree, by the causes which I have mentioned, than 



any other section of the country. Consequently, we 



find that, as low down as latitude 39°, rains are suffi- 

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