State Agricultural Society. 233 



woods to restrain the drops, which unite to denude the rocks of their 

 soil, and to form the mighty torrents, conveying thousands of tons of 

 detritus to fill up the rivers, as witnessed every Winter season. It can- 

 not be doubted but that an extensive planting of trees in the valleys, 

 at the head of the main ravines, where cachement-areas of twenty-two 

 thousand seven hundred and forty-two square miles have been hypothet'i- 

 cally plotted out, according to the projected irrigation plans of the 

 United States Commission, would superinduce a more humid condition 

 of the atmosphere, and lead to a more constant supply of water, in a 

 region now arid and desolate, for more than six months in the year. The 

 evaporation from such immense reservoirs as are contemplated by these 

 surveys, would be simply enormous, and, if intercepted by the trees 

 before being completely vaporized, the minute component vesicles of 

 water would coalesce upon the leaves and branches, and fall in drops 

 upon the earth. This is the mode in which trees might tend to increase 

 the humidity of the atmosphere, and which furnishes a rational and 

 potent reason for their general cultivation in the arid and semi-tropical 

 climate of California. 



The following tables of the meteorology of Sacramento and San Fran- 

 cisco, being representative types of the interior valley and coast climates 

 of California, are worthy of close study and attention: 



30— (agrl) 



