CLIMATE 



59 



129 days to mature in temperate latitudes, if taken farther north 

 gradually, after some years, reduce the period of life from sow- 

 ing to ripening to ninety daj's or less (1). The rapid develop- 

 ment of northern vegetation during the short summers is well 

 known. The same is true of alpine floras. Schimper's refer- 

 ence (56) to the effects upon the rate of gi-owth of trees and 

 the period required for their maturity may be cited in this 

 connection, and many other facts of similar import. 



The sunshine data for this region are far from being ade- 

 quate for our purpose but some facts can be given indicative of 

 the conditions. They show an abundance of clear days for the 



Table 8. The average sunshine record for four years (1908-1911) 

 in different parts of Montana. 



Station 



Miles City.. 



Havre 



Helena 



Great Falls 



Dillon 



Butte 



Plains 



Saltese 



Kalispell .. 



limited period to which they apply, though unfortunately the 

 distribution of the clear days by seasons can not be indicated, 

 nor the intensity of the light. In the state the average number 

 of clear days in the year varies from 160 to 178, the number 

 of those partly cloudy from 95 to 108, and those recorded as 

 cloudy from 83 to 101. At Poplar in northeastern Montana, the 

 number of clear days from year to year varies from 260 to 280, 

 those partly clear from 33 to 58, while the cloudy days at the 

 most cover less than two months, varying from 45 to 59 days. 

 These figures as well as those in the accompanying table are to 

 be taken only as a general indication, allowing for errors of 

 observation and the lack of related data. On the Western Slope 

 the clear days predominate in the summer and autumn, though 

 many are scattered through the other seasons. In eastern and 

 central Montana, the rains coming freely in the growing season 

 probably indicates a good many days during the summer at least 

 partially clouded. 



