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the temperature of the air and water is published, I feel confident 

 that it will be found that the southwest return trades prevail in 

 winter north of Cape Corrientes, and are turned by the mountains 

 and the coast up the Gulf of California, and so over this State as our 

 southeast winds. It comes from this gulf warm and laden with 

 moisture, and passes over the Colorado and Mohave Deserts. These 

 deserts, as shown by the meteorological records of the Smithsonian 

 Institute, have a mean winter temperature of from forty-eight to 

 fifty-six degrees. This is not sufficiently low to precipitate its moist- 

 ure, and it passes on until it meets the Sierra Nevada and Coast 

 Range. In ascending these it rises into cooler regions, finds a mean 

 winter temperature of forty degrees, and gives up some of its moist- 

 ure. When it flows down into the southern end of the great valley 

 of the Tulare, it meets a mean winter temperature of forty-eight 

 degrees, which is higher than that of the mountains it has just 

 passed. It therefore retains its moisture and passes on until it meets 

 a cold polar wind, and has another portion of its moisture condensed 

 in a rain-storm, or failing to meet this, passing still further north 

 until its moisture is condensed by the prevaling low temperature of 

 a higher latitude. It is of frequent occurrence in winter that a gentle 

 southeast wind will blow for days, giving no rain south of the lati- 

 tude of San Francisco, but cloudy weather at the northern end of the 

 Sacramento Valley, and light showers and rains from Red Bluff to 

 Oregon. Therefore, the northern part of the State should receive 

 more rain than the southern, and the mountains more than the val- 

 leys. The least rain should be in the hot deserts and on those sides 

 of valleys most sheltered by mountains from the moisture bearing 

 winds. 



THE FIRST PROPOSITION, 



That the northern part of the State should receive more rain than 

 the southern appears to be confirmed by the following exhibit of the 

 rainfall in the Sacramento, San Joaquin, and Tulare Valleys. These, 

 in fact, constitute one great valley ; all of it has the Sierra Nevada on 

 the east, and the Coast Range Mountains on the west. A line drawn 

 through its center in the line of the rain-bearing wind south-south- 

 east from Fort Reading to Sumner, would at all points be about an 

 equal distance from the ocean, and also an equal distance from the 

 Nevada Desert. All the stations relatively to their surroundings are 

 therefore similarly situated, and general laws have full operation 

 free from local disturbance. Commencing at the north end of the 

 valley: 



17 a 



