52 



VEGETATION OF A DESERT MOUNTAIN RANGE. 



6,000 feet only. In 1911 a series of stations was selected at vertical 

 intervals of 1,000 feet, from the base of the mountain, 3,000 feet, to 

 the station at 8,000 feet, and in 1912 a station was established on 

 Mount Lemmon, at 9,000 feet. These stations have been continued 

 in the succeeding summers. 



The readings of the gauges have been made at irregular intervals, as 

 opportunity afforded; the water has been protected from evaporation 

 by the use of kerosene, and has been measured volumetrically. The 

 installation of the gauges has been made each spring in time to secure 

 the first of the summer rain, and the final readings have been made in 

 September, closing in 1911 on the 22d to the 25th, in 1912 on the 28th 

 to 30th, in 1913 on the 25th to the 27th, and in 1914 on October 10th 

 to 11th. The location of the gauges at the various altitudes has been 

 such as to give them comparable topographic surroundings. Each 

 station is at the summit of a ridge with a commanding opening to the 

 south and without nearby trees. A record of rain has also been secured 

 at the Xero-Montane Garden at 5,300 feet, near the head of Soldier 

 Canon and just below the 6,000-foot station. A recapitulation of all 

 the readings of mountain rainfall is given in table 4. 



Table 4. — Summer Rainfall in the Santa Catalina Mountains. 



All readings cover the total precipitation of July, August, and September. Starred figures include 

 some October rainfall. Figures followed by plus are incomplete, owing to the overflowing of 

 gauges. 



The only record of daily rainfall for the Santa Catalinas is one 

 secured in Marshall Gulch, at 7,600 feet, from June to August 1911, 

 by Professor J. G. Brown, of the University of Arizona. A comparison 

 of the daily rainfall at Marshall Gulch and at 8,000 feet with that at 

 the Desert Laboratory (2,663 feet) for the period of these observations 

 is given in table 5. The number of rainy days on the desert was greater 

 than the number on the mountain top — 31 and 19 respectively — owing 

 to the 16 days with only a trace of rain at the Laboratory. The total 

 rainfall of the three months was 5.42 inches at the Laboratory (for 



