RIVER LANDS FOR VEGETABLES 25 



penses most moisture, and coolness over the lowlands which lie just 

 in its course as it rushes northward and southward 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 modified by the intrusion 

 from the coast, but this only acts in full measure during June, July 

 and August. It acts, therefore, as a moderator 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 pres- 

 ent 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 ocean air-currents from access to the 

 valley and then intense dry heat calls for ample water supply, which, 

 fortunately, however, is easily applied, because at such season the 

 rivers and sloughs are running full and if seepage is not enough, 

 siphons or flood-gates admit water from the high-running rivers, or 

 pumps yield great volumes at little cost. But the interior lowlands 

 have another more grievous trait. As they lie very low they are 

 the scenes of the latest spring and earliest autumn frosts and their 

 season for tender vegetables is shorter than that of the coast, though 

 with their higher heat and copious moisture their mid-season product 

 of these tender crops may out- volume a slower, longer season on 

 the coast. But the earliest and the latest tender vegetables do not 

 come from the interior lowlands. 



There are interior lowlands of wonderful producing capacity 

 at considerable distances from the confluence of the two rivers just 

 mentioned. For about three hundred miles the river lands extend 

 both northward and southward, offering an area of moist or easily 

 irrigated land of such fertility and extent that it suggests its own 

 ability to produce vegetables for the whole country. At present 

 hardly an appreciable fraction of one per cent of it is employed in 

 production for which it is best fitted. In the future its lower levels 

 will be the Holland and its upper extensions the Nile valley of Cali- 

 fornia. The farther these lowlands lie from the mouths of the rivers 

 the less they receive of coast influences. This gives the distant low- 

 lands a higher temperature and greater forcing power upon vege- 

 tation. The nights are warm as well as the days. Vegetables of 

 prodigious size and acre-crops which tax credulity, are the result of 

 the favoring conditions. But these lands are low and danger of frost 

 makes it necessary to select crops for hardiness during a part of the 

 year. 



Interior Plains and Foothills. Above and away from the low- 

 lands of the rivers and their deltas the interior plains stretch far as 



