FOREST TYPES IX CENTRAL ROCKV MOUNTAINS. 



29 



Temperature. 9 at the control station. — The air-temperature record 

 for the control station, representing atmospheric conditions 20 feet 

 above the ground and in all probability mean conditions for this 

 elevation (8,836 feet) and locality, little affected by local exposure 

 and other circumstances, extends from January, 1910, to April, 1921, 

 inclusive, with the exceptions already noted. For the most part 

 these records were compiled and comparisons between the types 

 were made on the basis of data secured to the end of March, 1918. 

 Such comparisons seem quite adequate but to arrive more nearly 

 at normal absolute temperatures records secured since March, 1918, 

 will sometimes be used. The constant use of a thermograph and 

 of standardized thermometers has made this a very satisfactory 

 record. It has been very carefully checked over since its compila- 

 tion, as secured month by month, so that little error is likely to 

 remain in it except that inherent in the short method of computing 

 means. 



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Fig. 1. — Air temperatures at control station by 10 day periods. (F-l) Elevation 8,836 feet . 



Mean air temperatures. — The complete record of mean air tem- 

 peratures for the control station is given in Table 2, by decades 

 and months, for the purpose of showing the possible variation in 

 corresponding periods of different years, as well as the constancy of 

 certain conditions which are of interest. The average temperatures 

 are shown in Figure 1 . 



Note. — All original records of air temperatures for decades, months, and 

 years are carried to two decimal places. Hence, some of the means given in 

 the following tables, do not agree precisely with the 1-place figures from which 

 they are apparently derived. In dropping hundredths to sa\e space in these 

 tables, the rule is followed of throwing 0.05 to the nearest even tenth. Thus 0.45 

 becomes 0.4 and 0.55 becomes 0.6. 



