RAINFALL IN CALIFORNIA. 15 



where that the conditions permit of it, our grass crops 

 may, by means of irrigation, be made equal to those of 

 the most favored climates, and that the productiveness 

 of our meadows may be increased greatly beyond that 

 which is now possible by the most skillful culture. 



But a large portion of our territory is practically rain 

 less and arid. The configuration of the surface is such, 

 that the passage of rain clouds is arrested by high moun 

 tains, and the precipitation is confined to very small and 

 elevated areas. This is the case with nearly the whole 

 of our territory west of the 100th meridian of longitude, 

 or a line drawn through the western part of Kansas and 

 Nebraska, from north to south. In this extensive district 

 are found some of the richest soils in the world, which 

 will yield, with irrigation, a yearly average of 30 to 40 

 bushels of wheat per acre. During the growing season 

 the rain-fall is the least ; the greatest amount taking 

 place in the winter months in the form of snow. 



The amount of the rain-fall decreases from the 100th 

 meridian, where it is less than 20 inches in the year, to 

 7 to 15 inches further west, and increases as the Pacific 

 Coast is reached, where it measures 9 1 1 4 inches in Southern 

 California up to about 23 inches at San Francisco. But 

 the fall is very irregular, depending greatly upon local 

 causes. This is shown by the following facts, derived 

 from scientific observations at various points in Cali 

 fornia, where the contiguity of the coast range of moun 

 tains with that of the Sierra Nevada causes many very 

 surprising differences in the amount of the rain-fall. 

 Thus while at San Francisco the fall averaged 23 inches 

 yearly during 19 years, 14 miles distant at Pillarcito s 

 Dam it averaged during nine years, 58 inches yearly. 

 This irregularity is intensified by the dry winds which 

 absorb moisture to an extraordinary degree ; a north wind, 

 hot and dry, which occasionally blows in the San Joaquin 

 and other vallies, has evaporated one inch of water in a day. 



