CALIFORNIA'S FORTUNATE SITUATION 11 



changes are therefore much less excessive. This characteristic of 

 our local climates is due in the main to two great agencies, one active, 

 bringing heat, the other passive, shielding us from arctic influences. 



First: Our proximity to the Pacific Ocean. Professor Alexander 

 G. McAdie, for twenty years in charge of the San Francisco office of 

 the United States Weather Bureau, and now Professor of Meteorology 

 at Harvard University, says of the mildness of the California 

 climate: "The Pacific Ocean is a great natural conservator of heat, 

 the mean annual temperature of which near the California Coast 

 ranges from 50 degrees to 60 degrees F. The strength of the westerly 

 winds which prevail on the California Coast for more than half the 

 days of the year is due to the fact that the whole drift of the atmos- 

 phere is prevailingly from the west to east. The climate of west 

 coasts is consequently less severe than the climate of east coasts."* 



Second: Another agency contributing to the mild climate of 

 the Pacific Coast consists in the the mountain barriers upon our 

 northern and eastern boundaries. It was Guyot who first called 

 attention to the fact that the Sierra Nevada and the Cascade Mountains 

 reach the coast of Alaska and bend like a great arm around its 

 western and southern shore, thus shutting off or deflecting the polar 

 winds that otherwise would flow down over the Pacific Coast States, 

 while California has her own additional protection from the north in 

 the mountain arch which has its keystone in Mount Shasta. 



CHIEF TOPOGRAPHICAL AND CLIMATIC DIVISIONS 



OF CALIFORNIA 



California is usually divided into three main areas and climates, 

 each distinct in typical conditions and yet separated by regions, more 

 or less wide, in which these conditions merge and influence each other. 

 Dr. Robertson says :f 



Isothermal lines which normally run east and west are, as they near the 

 Pacific, deflected north and south, and define three distinct climatic belts. These 

 may be named coast, valley and mountain ; and while they resemble each other in 

 having only two seasons, they are dissimilar in other respects. These differences 

 depend upon the topography of the country, and are of degree rather than of 

 kind; altitude, distance from the ocean, and situation with reference to mountain 

 chains, giving to each region its characteristic climate. 



How similar are the conditions which prevail in these belts may be 

 learned from the data shown in the following table, which includes 

 points separated by nearly the whole length of the State, the difference 

 in latitude of the extreme north and south points being seven or eight 

 degrees. Thus, through a north or south distance great as that which 

 separates the States of Georgia and New York, similar climatic 

 conditions prevail in California. In the following table the averages 

 are deduced from observations by the United States Weather Bureau 

 observers for a long series of years : 



*"The Rainfall of California," University of California Publications in Geography, 1914. 

 tReport of State Agricultural Society, 1886, page 322. 



