THE INTERIOR LOWLANDS 31 



before they reach the lands. In all this vast region, then, similar 

 conditions prevail, locally modified, however, enough to create some 

 marked differences in degree, which have been well utilized as the 

 basis of special production. Temperature rises and rainfall de- 

 creases as you proceed southward. And yet though these differ- 

 ences may notably localize production, the whole coast region north 

 and south has this in common; it has a more equable and lower 

 temperature and a more generous rainfall than the interior valley 

 at its own latitude ; it also has lighter frosts, growing lighter still to- 

 ward the south until it incloses regions here and there which favoring 

 topography makes practically frostless. Such situations favor all- 

 the-year growth of the tenderest vegetables, and perennial beans 

 and tomato trees are possible. The coast region of the state is, as 

 stated above, the chief vegetable-producing region. 



Interior. Lowlands. The region next in importance in vege- 

 table production comprises the lower lands of the interior valleys. 

 They lie along the two great rivers of the northern and central 

 parts of California the Sacramento and San Joaquin and their 

 tributaries. These rivers flow from nearly two hundred miles, 

 north and south of their confluence, where they mingle their waters 

 through numerous sloughs until the joint streams pour through 

 a gap in the coast range into San Francisco bay. The same gap 

 which lets out the waters lets in the ocean current of moisture- 

 laden wind and moderates the heat of the entire interior valley, 

 but naturally dispenses most moisture, and coolness over the low- 

 lands whidi lie just in its course as it rushes northward and south- 

 ward to displace the air which is rarified by the sun heat on the 

 interior plains of the great valley. These interior lowlands along 

 the lower stretches of the rivers have then an interior climate modi- 

 fied by the intrusion from the coast, but this only acts in full meas- 

 ure during June, July and August. It acts, therefore, as a mod- 

 erator of heat and drought during that period and supplements the 

 supply of aqueous vapor which rises by evaporation from the 

 immense acreage of tule swamps and shallow lakes which surround 

 the tillable lands of the region. Climatic conditions in this large 

 interior area favor the growth of vegetables and its producing 

 capacity is beyond any present commercial use which can be made 

 of it. But though it has a temporary coast modification, as has been 

 stated, it falls back into interior habits when restraint is removed. 

 It has intervals of hot, dry winds which exclude the coast winds 



