Central Part of British North America. 217 
clouds being seen to pass right across it in upper air. This 
wind must not be too rigidly defined by its mere direction, 
as it often blows from anomalous quarters, while its char- 
acter remains the same, being quite subordinate in form 
to either of the next two groups, which are both stormy 
winds. 
2. This group includes all the winds that generally blow 
from between north and east, and which in winter bring snow, 
and in summer cold fogs. 
3. The south and south-west winds, that, blowing from the 
Pacific Ocean through and over the Rocky Mountains, always 
bring clouds, warmth, and sometimes even rain during the 
winter. 
The struggle among these three climatic agencies gives 
rise to the following succession of phenomena. A few days 
of fine, steady, though perhaps intensely cold weather, with 
the wind from the north-west, is followed by a slight rise in 
the temperature, caused by the north-east wind having piled 
a canopy of cloud over the lower stratum, and so preventing 
radiation. This is effected gradually, every morning the sky 
being more and more overcast, and clearing later in each suc- 
cessive day, until at length it remains cloudy till evening, 
when a cutting north-east wind commences, that soon increases 
to a storm, followed by snow. This lasts for two or three 
days, till the snow begins to fall more gently, and with the 
temperature rising, at length the clouds break, when the upper 
stratum of air is seen moving rapidly from the south-west, carry- 
- ing light fleecy clouds against a clear sky. Generally, in the 
course of the following night, the south-west wind affects the 
lowest stratum of air, and increases in violence, sometimes 
ranging rapidly through many points of the compass, showing 
that it takes the form of a cyclone, and at the same time 
bringing a high temperature and dense clouds discharging 
rain. One of these storms, for instance, passed over the Sas- 
katchewan Plains on the 3d of January 1858 ; and at Edmon- 
ton the minimum temperature for that day and night was 36°, 
while the maximum for the next twenty-four hours was only 
10°. Again, on the 24th of the same month, at the close of 
another of these storms, the temperature fell from 37° at 4 
