32 THE CLIMATOLOGY OF THE UNITED STATES. 



considered later. Having reached the Sierra Nevada 

 range, we find the western slopes very much more abrupt 

 than those of the Rocky Mountains, and we descend very 

 rapidly into the valleys of California. We are now in a 

 region which possesses well marked climatic peculiarities. 

 The state of California is about eight hundred miles 

 Ions: and two hundred miles wide, with a coast line of 



O 



a little over one thousand miles. Its surface is cut up Try 

 mountain ranges running parallel with the coast, and di- 

 viding the state into numerous long narrow valleys. 



The prominent features of the climate are, first, a wet 

 and a dry season ; the former occurring in the winter 

 months, while from May to October rainfalls are rare, and 

 a shower in June, July or August, is of very unusual 

 occurrence. Secondly, a small rainfall, the amount of 

 precipitation in the rainy season being no greater than that 

 of the corresponding period in New England. Thirdly, 

 mild winters, snow being a rarity except in the mountains, 

 and the climate in the southern part of the state being of a 

 semi-tropical character. 



The first question which would naturally arise would be 

 in regard to the cause of the dry season. A person in the 

 east is very apt to consider that the same causes tend to 

 produce precipitation either in the form of rain or snow in 

 all seasons, and when one finds a region where the rain 

 ceases in the spring and does not begin again until fall, 

 curiosity is aroused as to the peculiar conditions which 

 cause a cessation of rainfall during a part of the year. In 

 considering this question, several important facts must be 

 borne in mind. In the first place, there is a tendency for 

 weather changes to move in an easterly direction ; and, 

 secondly, the western sides of the continents are milder 

 than are the eastern sides in the same latitudes. This 

 may be partly due to the influence of warm oceanic cur- 



