26 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



For the most part the Cohiiiibia River hiva completely covered up 

 all of the older rocks over which it flowed, these being seen only as 

 they are revealed in the river canyons. Exceptions to this appear in 

 peaks which were too hii>li to be overwhelmed, as in the cases of 

 Steptoe and Kamiak buttes in Whitman County, together with many 

 others less conspicuous. Steptoe Butte is a granitic cone projecting 

 about 500 meters above the surrounding l>asalt and, being completely 

 isolated, is a notable landmark. To designate such isolated buttes, of 

 wdiich there are many, Ivussell has proposed the term steptoe^ after 

 the name of this striking example. A steptoe is '" an island of granite 

 in a sea of basalt." Kamiak butte near Pullman is composed 

 largely of quartzite. 



THE BLUE MOUNTAINS. 



The Blue Mountains in extreme southeastern Washington and ad- 

 jacent Oregon, represent a great uplift of basalt surrounding a 

 central mass of granite peaks. The portion of these mountains in 

 Washington is composed Avholly of basalt, elevated to over 2,000 

 meters. 



The granitic peaks in the central part of the mountains, the so- 

 called PoAvder River Mountains in Oregon, rise to an altitude of 

 about 3,000 meters, and form the greatest "steptoe" in the wdiole 

 Columbia Basin. 



CLIMATE. 



The data here presented are compiled from the reports of the 

 United States Weather Bureau. The observing stations are all 

 located at places of relatively low altitude, and the accurate data 

 therefore relate wholly to the portions of the State wdiich lie in the 

 Transition and Upper Sonoran areas. 



PRECIPITATION. 



The following table gives the normal annual rainfall of each of 

 the Weather Bureau stations together with the length of the period 

 over which full records are available : 



