12 



METEOROLOGY. 



greatest reduction of temperature after the hour of maximum elevation. However high the 

 wave of temperature towers up under the influence of a vertical sun and cloudless sky, it sinks 

 proportionately low during the night, rendering it cool and chilly." The range of difference 

 is there sometimes 41° in July, and the mean range for that month 22.07. The range for the 

 three summer months is 19.57 or 79.73 for the greatest heat by day, and GO. 82 ibr the 

 mean coldest hour of the night. This evidently arises from the fact that the more the air is 

 rarefied and ascends by day, the more cold air from the neighboring snowy mountains must 

 rush down to take its place at night, until, as in August, even that of the mountains becomes 

 so heated that the minimum range of 16.34 is reached. His table is the result of two years' 

 observations. The range will be less in direct ratio to the distance of any given place from 

 the snowy or lofty mountains. It is probably, also, less where, as in this Territory, the greatest 

 heat by day differs least from the mean, or from the mean temperature of the neighboring- 

 mountains. 



One of the greatest agricultural advantages of the climate near the Pacific coast is in the 

 earlier commencement of spring and later coming of winter, which makes the growing season at 

 least a month longer, and prevents the droughts of summer from seriously interfering with 

 cultivation. 



This fact is shown to exist by the comparison of the means for the three winter months, as 

 already made in the tables of climate in places of similar annual temperature. It is also well 

 known to characterize and influence materially the processes of agriculture in California and 

 elsewhere. To demonstrate its application to the region now under consideration I give a table 

 of comparison of February, March, and December, with places already iised in this connexion: 



Bitter Boot valley, means of two years. 



Rochester, New York, 24 years 



Detroit, Michigan, 13 years ., 



Beloit, Wisconsin, 6 years 



Fort Snelling, Minnesota, 35J years 



Fort Benton, Nebraska, 1 year 



Laperai, 2 J years 



Walla- Walla, 1 J years 



Dalles, 6 years 



Vienna, Austria 



Philadelphia, 20 years 



Washington, 13 years 



St. Louis, 23 years 



Cincinnati, 20 years 



February. 



o 



30.7 

 26.4 

 26.6 

 25.8 

 17.6 

 26.6 

 3S.8 

 34.5 

 40.0 

 33.5 

 36.3 

 36.7 

 35.0 

 34.1 



March. 



o 



35.5 

 33.1 

 35.4 

 33.8 

 31.4 

 36.2 

 42.7 

 42.7 

 46.4 

 40.8 

 45.6 

 45.3 

 44.0 

 43.5 



December. 



o 



29.5 

 28.5 

 26.9 

 24.0 

 16.9 

 33.0 

 40.4 

 38.6 

 83.7 

 33.0 

 27. 1 

 37.3 

 33.6 

 34.5 



We thus find that cultivation may be commenced some days earlier in the Territory than at 

 places several degrees further south in the Atlantic States, and some weeks earlier than in places 

 of the same latitude. Allowing for the close vicinity of all the western territory posts to 

 mountain ranges, we may suppose that a still greater difference exists in certain localities on 

 the Great Plain, where the greater dryness of summer also requires an early cultivation for 



