CLIMATE OF THE SANTA CATALINA MOUNTAINS. 81 



very dissimilar in their topographic location. In table 17 it will be 

 seen that the winter minimum at Flagstaff, in northern central Arizona, 

 was 21° below the minimum for Marshall Gulch, although Flagstaff is 

 located 700 feet lower. This relation is similar to that which exists 

 between the length of frostless season at Marshall Gulch and at Flag- 

 staff, and is due to the facts mentioned in that connection on page 74. 

 At the Fort Valley Experiment Station, located in the vicinity of 

 Flagstaff and nearer to the San Francisco Peaks, the winter minimum 

 was 4° lower than at Flagstaff. At Snowflake, on the extensive Mogol- 

 lon Plateau, and at Fort Apache, in the cold-air drainage of one of the 

 main forks of the Salt River, there were also minima which were 

 respectively 9° and 3° lower than at Marshall Gulch, although these 

 stations are respectively 2,000 and 2,400 feet lower than Marshall 

 Gulch. Fort Huachuca is located at the base of the Huachuca Moun- 

 tains in such a manner as to escape cold-air drainage from any of the 

 large cafions of that range of mountains, and its absolute minimum was 

 6° higher than that of Fort Apache, which is of approximately the same 

 elevation. Chlarson's Mill is situated in Frye Caiion in the Pinaleno 

 (Graham) Mountains, surrounded by heavily forested slopes. Its loca- 

 tion is analogous to that of Marshall Gulch, being similarly situated 

 in an isolated desert mountain and surrounded by heavily forested 

 slopes. The single monthly minimum available for Chlarson's Mill 

 is 15°, for a month in which the minimum at Tucson was 18°, while 

 it was 7° for the Fort Valley Experiment Station, at almost the same 

 elevation as Chlarson's Mill. 



An inspection of the absolute minima for 1913-14, in table 17, will 

 show that the same relations hold true between the several stations 

 that have just been discussed. The winter minimum for Tucson, 26°, 

 was much higher than in the preceding winter, and so was that for 

 Marshall Gulch, 15.5°, although the absolute minimum in the new 

 station on the fire tower at Mount Lemmon was 3°, and in the heavy 

 timber on the north face of Mount Lemmon was 5°. 



The data just discussed amply bear out the statement that the lowest 

 temperatures of winter are less severe on the Santa Catalinas than 

 they are at the same elevation on the plateau of north-central Arizona, 

 and even less severe than they are in many situations of lower altitude. 

 The fragmentary records of earher years at Chlarson's Mill, which 

 are not given here but are available in publications of the Weather 

 Bureau, show that it is likewise favored by lower winter temperatures 

 than are the plateau stations of the same elevation in Arizona. The 

 length of the frostless season has just been shown to be less in the Santa 

 Catalinas and in the Pinaleno Mountains than at Flagstaff. In short, 

 the indications are very strong that all phases of winter temperature 

 conditions are less severe on the small and isolated desert mountains 

 than on the plateaus and highlands of the same elevations and of nearly 



