INCHES: 
‘24, 
56 VEGETATION OF A DESERT MOUNTAIN RANGE. 
Figure 6 gives the actual curves for the three summers for the Santa 
Catalinas. It will be noted that in each curve there is a sharp rise 
from 3,000 to 4,000 feet, a rise which continued at the same gradient 
to 5,000 feet in 1911 and 1913. From these submaxima, reached at 
5,000 feet in 1911 and 1913 and at 4,000 feet in 1912, there is a fall to 
a subminimum at 6,000 feet in the two former years and at 5,000 feet 
in the latter year. There is then a pronounced rise in the curve to 
7,000 and 8,000 feet. The rainfall at 9,000 feet in 1912 was probably 
an inch or more greater than indicated by the curve, in any case was 
greater than that at 8,000 feet; whereas in 1913 the precipitation at 
9,000 feet was less than that at 8,000 feet, in fact less than that at 
5,000 feet. 
The horizontal distances between the rainfall stations were unequal 
(see plate A), the angle of rise from 3,000 to 4,000 feet being very 
INCHES. 
20 
n 4 n 1 rn 1 
2,000 3,000 4,000 5,060 €,000 700 
Fig. 7.—Graph showing vertical increase of summer rainfall in the Santa Catalina Mountains 
in 1911 (solid line), together with averaged vertical increase in a series of 13 Weather Bureau 
stations in Arizona (broken line). 
Fie. 8.—Graph showing vertical increase of summer rainfall in the Santa Catalina Mountains 
in 1912 (solid line), together with averaged vertical increase in a series of 21 Weather Bureau 
stations in Arizona (broken line). 
sharp, that from 4,000 to 5.000 slightly less sharp, and that from 5,000 
to 6,000 still less sharp and exactly equal to the angle of rise from 6,000 
to 7,000 feet. The stations at 8,000 and 9,000 feet are located at the 
west end of the main ridge and are consequently not in line with the 
lower stations. The sharp rise in elevation between the 3,000 and 4,000 
foot stations is doubtless partially accountable for the rapid increase 
of rainfall between them. The steep rise of the rainfall graphs between 
6,000 and 7,000 feet may indicate an influence due to the position of 
the 7,000-foot station on the north rim of Bear Cafion, with a very 
abrupt wall immediately below it. There is no topographic cause, 
however, to which it is possible to attribute the dip in the rainfall 
curves for 6,000 feet in 1911 and 5,000 feet in 1912. 
In order to institute a comparison between the mountain gradients 
of rainfall and those of the valley stations of the Weather Bureau the 
data have been collated which are expressed in the curves of figures 7 
1 A 1 i 
2,000 3,000 4,000 5,000 6,000 7,000 = @,C0 00 
000 
