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water over which it is passing. The gulf stream opposite San Fran- 

 cisco is but two degrees and forty-eight one-hundredths colder for the 

 year than the water at latitude thirty-two degrees, longitude one hun- 

 dred and eighty degrees, for the same time. 



This difference, if uniform, would hardly create fogs, but it is not 

 uniform. It frequently happens that the water and air outside this 

 gulf stream are warmed to sixty-five degrees, or a few degrees higher ; 

 the moisture in this air passing over our gulf stream when it is fifty- 

 five degrees or lower, is condensed, and produces the fogs that bathe 

 the sides of the hills west of the summits of the Coast Mountains. If 

 these fogs pass the summits they meet the heat of the valleys and are 

 dissipated. It is evident that this gulf stream, where it passes the 

 coast of Alaska, British Columbia, and Washington Territory, is very 

 much warmer than the water of the surrounding ocean. The moist- 

 ure in the air passing over it is condensed, not only into fogs but 

 heavy rains. As this gulf stream comes south it is constantly arriv- 

 ing at a part of the ocean where the temperature more nearly 

 approximates that which it holds. Opposite San Francisco, as has 

 been shown, it is colder than the surrounding ocean. At some vary- 

 ing point north of San Francisco its temperature must be the same 

 as the ocean, and, therefore, in that region fogs cannot be so preva- 

 lent. If the variation of temperature between the gulf stream pass- 

 ing this coast and the surrounding ocean were greater, we should 

 have rains in addition to fogs from the westerly winds: as it is, this 

 gulf stream exercises a marked influence on all those portions of the 

 coast counties lying west of the main divide of the coast range of 

 mountains. The rainfall is more on the coast than in the Sacra- 

 mento and San Joaquin Valleys in the same latitudes. To exhibit 

 this I have selected a series of stations near the coast south from San 

 Francisco. 



San Mateo and Modesto are nearly in the same latitude. Modesto 

 has an annual mean of nine and sixty one-hundredth inches of rain, 

 while San Mateo has fifteen and seventy-four one-hundredths. San 

 Jose and Merced are in the same latitude; the former has ten and 

 twenty-four one-hundredths inches, and the latter nine and thirty- 

 six one-hundredths inches. As we go further south the discrepancy 

 between the coast and interior valleys is still more marked. Soledad 

 and Tulare have the same latitude. Soledad gets a mean of eight 



