80 



VEGETATION OF A DESERT MOUNTAIN RANGE. 



Arizona at an elevation 700 feet lower than that of the 7,600-foot 

 Station in Marshall Gulch. The extremely low temperatures at the 

 Arizona Experiment Station and the office of the Desert Laboratory, 

 as contrasted with the minimum temperature of 17 at the Desert 



TABLE 16. Absolute minimum temperatures of two winters at stations in the Santa Catalina 



Mountains and at Tucson. 



Laboratory, are to be accounted for through the operation of cold-air 

 drainage. On the coldest night in January 1913 there was a difference 

 of only 3 between the temperatures of the Santa Cruz Valley and 

 Marshall Gulch, 5,400 vertical feet apart. It is desired here not so 



TABLE 17. Absolute minimum temperatures of winter months for two winters at selected 

 stations in Arizona, together with the absolute winter minima at 7,600 feet in the Santa 

 Catalina Mountains. 



much to lay emphasis on the exceptional coldness of the Santa Cruz 

 valley, but on the exceptional warmness of the summit of the Santa 

 Catalinas, as contrasted with similar elevations in Arizona which are 



