268 TRANSACTIONS OF THE 



ten), the temperature fell to 25°, according to the railroad weather reports. 

 — Sergeant Barwick.] There is a remarkable uniformity in the climate 

 throughout the Sacramento Valley. In it, a difference of 5° of latitude, 

 between 35° 30' and 40° 30', only lowers the annual average temperature 

 4.15°. The difference of the annual average temperature between corre- 

 sponding degrees of latitude in the Atlantic States, at an equal distance 

 from the ocean, is more than 8°. It has been found that the foothills of 

 the Sierra, up to a height of about twenty-five hundred feet, have apparently 

 the same temperature as places in the valley having the same latitude. It 

 has also been found that with increased elevation there is an increase of 

 rainfall over those places in the valley having the same latitude, as, for 

 illustration, Sacramento, with an elevation above the sea of 30 feet, has an 

 annual average temperature of 60.48°, and an average fall of rain of 

 between eighteen and nineteen inches, while Colfax, with an elevation of 

 two thousand four hundred and twenty-one feet, has an annual average 

 temperature of 60.50°, and an average annual rainfall of from forty-two to 

 forty-three inches. This uniformity of temperature and increase of rain- 

 fall appears to be the law throughout the whole extent of the foothills of 

 the Sierra, with this variation as relates to temperature, viz.: as latitude is 

 decreased the temperature of the valley is continued to a proportionally 

 greater elevation. To illustrate, approximately: if the temperature of 

 Redding, at the northern end of the valley, is continued up the foothills to 

 a height of two thousand feet, then the temperature of Sacramento, in the 

 center of the valley, would be continued up to two thousand five hundred 

 feet, and that of Sumner, in the extreme southern end of the valley, up to 

 three thousand feet. The increase of rainfall on the foothills in the lati- 

 tude of Sacramento, due to elevation, is about one inch to each one hun- 

 dred feet. South from Sacramento the proportion decreases until, at 

 Sumner, the increase due to elevation is but half an inch to each one hun- 

 dred feet. This is shown by the record kept at Fort Tejon, in the Tehachapi 

 Mountains near Sumner, at an elevation of three thousand two hundred 

 and forty leet, where the annual rainfall is between nineteen and twenty 

 inches. There is no record kept at any point in the hills above Redding, 

 but probably in this latitude the increase due to elevation is about one and 

 a half (lij) inches to each hundred feet. The increase of precipitation on 

 the hills at the northern end of the valley gives greater density to the for- 

 ests, and permits them to grow at lower elevations than in the southern 

 end of the valley. At the same time the difference in temperature is so 

 small that the character of the vegetation of the hills at each end of the 

 valley is not dissimilar. The trees found in the vicinity of Redding, at 

 the northern end of the valley, below an elevation of five hundred feet, are 

 not found at the southern end until we pass Caliente, at an elevation of 

 one thousand three hundred feet. If would seem that the temperature of 

 the valley prevails up the Sierra to an elevation that equals the height of the 



COAST RANGE OF MOUNTAINS. 



If a line were drawn parallel to the surface of the ocean from the top of 

 the Coast Range, east, until it met the flanks of the Sierra, it would mark a 

 level on the Sierra below which the temperature would not materially differ 

 from that in the 



SACRAMENTO VALLEY. 



This fact is probably to be ascribed to the prevailing southwest return 

 trade winds which blow over the State from the ocean for more than three 



