76 



VEGETATION OF A DESERT MOUNTAIN RANGE. 



minimum temperatures at the several stations are the only ones that 

 have been used, and they have been in all cases compared wdth the 

 minimum for the same period at the Desert Laboratory. The average 

 differences between the minima of the mountain stations and those of 

 the Laboratorj'^ are shown in table 13, and it is these differences that 



have been used in the construction of the graph in figure 16, which 

 shows the gradient for the Santa Catalinas, the average gradient for 

 17 mountain ranges in different portions of the world (according to 

 Hann), the gradient for Pike's Peak, the Sierra Nevada, and also the 

 gradient in the free air, as determined at the Blue Hill Observatory. 



