164 AGRICULTURE ON THE PACIFIC SLOPE 



the Pacific Ocean, but are formed whenever a moist 

 wind crosses a high mountain range and, having lost 

 most of its moisture in going up the west slope, comes 

 down on the east side of the mountains, and gets 

 warmed by compression as it descends; for pressure 

 always causes a rise of temperature. The temperature 

 of these winds rarely rises above 40 degrees Fahr., but 

 when the rise occurs from 30 degrees below zero within 

 a few hours, or less, it makes us think the wind quite 

 warm. The Chinook 1 sometimes saves trees, crops, 

 and even people from being killed by cold. 



WEATHER IN THE GREAT BASIN 



Farther south in the Great Basin, in Wyoming, 

 Utah, western Colorado, and New Mexico, the total 

 rainfall in the level country, which is from three to four 

 thousand feet above the sea level, ranges from twelve 

 IQ fifteen inches; so that where irrigation water cannoTT 

 be had, "dry farming" (page 49) is the only way to 

 raise crops. This means that the soil surface must 

 always be kept open for the rains to soak in, and made 

 loose again after rains by harrowing, if a crust has 

 formed. In this way very good grain crops can be 

 grown at least every other year, as the soils are very 

 rich. 



1 The word Chinook is now applied in different parts of the country 

 to warm " foehn" winds. Originally the term was applied to a north- 

 west wind from the coast region inhabited by the Chinook Indians. 



