CLIMATE OF THE SANTA CATALINA MOUNTAINS. 



65 



curves show the averages between the south and north slopes for each 

 station at each reading, being expressed in cubic centimeters of evapo- 

 ration per day. Here again is brought out the pronounced fall in 



Fia. 11. — Graphs showing seasonal march of evaporation rate at 6 altitudes in the Santa Cata- 

 linas in 1911. Amounts are average daily losses from the atmometer, and each reading is 

 the average of one on a north slope and one on a south slope. 



rate which follows the advent of the summer rains and the cloudy 



and relatively humid weather by which they are accompanied. After 



the period of heavy rains by which the 



humid mid-summer was opened in the last 



days of June and early days of July there 



was a sUght rise in evaporation, followed 



by a slight fall in late August and early 



September. The curves for 3,000 and 



4,000 feet accompany each other closely 



after the first two readings, and the curves 



for 6,000 and 7,000 feet accompany each 



other closely throughout the summer. 



The curve for 8,000 feet stands always 



well apart from that for 7,000 feet. The 



grouping of these curves is, therefore, 



analogous to the natural subdivisions of 



the vegetation. The readings taken in the 



Desert region at 3,000 and 4,000 feet, those taken in the Encinal and the 



lower edge of the Forest at 5,000, 6,000, and 7,000 feet, and the one series 



Fig. 12. — Graphs showing altitudinal 

 decrease in rate of evaporation in 

 the Santa Catalinas in arid fore- 

 summer (heavy line) and humid 

 mid-summer (light line) of 1911. 



