396 United States. 



4. The plateau, rising towards the Kocky Mountains 

 from 1,000 to 5,000 feet above sea level, some 870,000 

 square miles in extent, a region of scanty rainfall, 

 hence of prairie and plain, but mostly rich soil of un- 

 determined depth, capable of prolific production where 

 sufficient water supply is available. 



5. The Eocky Mountain region, rising from 5,000 to 

 near 10,000 feet (except some higher peaks), an arid to 

 semi-arid district of rugged ranges, covered mostly 

 with forest growth, often open and of inferior kind, 

 with tillable soils in the narrow valleys, requiring ir- 

 rigation for farm use; a mining country, rich in gold 

 and silver, extending over 150,000 square miles. 



6. The Sierra Nevada Mountain Eange, including 

 the Coast Eange, rarely over 7,000 feet elevation, arid to 

 semi-arid on the Eastern slopes; humid, and support- 

 ing magnificent forest growth on the Western slopes; 

 some 190,000 square miles. 



7. The Interior Basin, lying between the two preced- 

 ing mountain ranges, some 400,000 square miles; for 

 the most part a desert, although in parts supporting a 

 stunted growth of pinon and juniper, and, where ir- 

 rigation is possible, productive. 



8. The interior valleys of the Sierra, comprising 

 about 30,000 square miles, which, under irrigation, 

 have become the garden spots of the Pacific. 



To these topographic subdivisions correspond in 

 part the climatic and the forest conditions, although 

 variation of soil and of northern and southern climate 

 produce further differentiation in types, and in distri- 

 bution of field and forest. 



