INTRODUCTION. x } v 



and westward, and seldom from the east. The moisture at Nisqually 

 represents that of western Oregon, it was found to be '835. The pho- 

 tometer at noon, the mean of several days' observations, stood at 77, 

 and during the night 0. 



The middle section of Oregon is much drier; the temperature has 

 an annual range, of from 18 to 100 Fahr. ; the daily range is about 

 40. The character of the vegetation is quite different from that of 

 the western, it gives proof of both the excessive dryness and barren- 

 ness of the soil ; there are no dews, and rain seldom falls from May to 

 November, but during winter there is much rain and snow. Eastern 

 Oregon is still more remarkable for its fluctuations of temperature. 

 The Rev. Mr. Spalding favoured us with a meteorological diary for 

 1837-40; these observations are given on the diagram, Plate XVIII., 

 page 568. They were made at Lapwai, on the Kooskooski River, in 

 latitude 46 27' north. Lapwai is about 2000 feet above the level of 

 the sea, but it is situated in the valley of the Kooskooski, which is 

 2000 feet below the general level of that part of the country. From 

 the various accounts I have received of this part of Oregon, I incline 

 to believe, that the observations here represent very nearly the ther- 

 mometrical changes of that section of the country. The mean monthly 

 temperature, as the diagram will show, is almost a regular curve for 

 the year ; but it alone would give a very imperfect idea of the cli- 

 mate ; I have therefore added the extremes of temperature which 

 take place during the month. The range of the thermometer, even in 

 July and August, varies from 24 to 108 ; the days on which the 

 great extremes occur are marked at the points of the lines, the scale 

 to which they refer being the inner one on the left hand column ; 

 there are few months in which the lowness of temperature would not 

 indicate frosts, yet these do not occur. The climate is regarded as a 

 moist one ; in winter there is much snow, and in summer much rain 

 falls ; the nights are always cool. The thermometer falls in January 

 to 10, but this is a rare occurrence. In July it reaches the highest 

 point, often rising to 107 or 108, and in the sun standing at 144. 

 The greatest monthly and daily range in the two years was 88 and 

 58. According to Mr. Spalding, the grass remains green all the year, 

 yet irrigation is found necessary to cultivate the crops. Mean annual 

 temperature 53 Fahrenheit. 



At Vancouver, Dr. M'Laughlin was kind enough to keep a meteoro- 

 logical diary during the stay of the Expedition; this has afforded me 

 an opportunity of making the comparison between the western and 



12 



