218 Dr James Hector on the Physical Features of the 
P.M., to 13°.5 before midnight, or a difference of 50°.5 in eight 
hours. 
After the storm from the south-west has passed, the light 
north-wester generally sets in irregularly, and the temperature 
falls in the course of a few days to an extreme, during which 
there is calm, followed by the haze and the overhanging cloud 
from the north-east as before. 
Along the eastern base of the Rocky Mountains these 
changes are even more distinctly marked than in the longitude 
of Edmonton, and the effect they have in reducing the amount 
of snow is very remarkable, so that there is a narrow tract 
close to the mountains where there is never more than a few 
inches of snow on the ground, and the rivers, when rapid, 
remain open during the winter. In consequence of this, a few 
ducks are found to linger throughout the whole season in the 
mountains, while from the Plain country, in latitudes much 
further south, they are necessarily absent from October till 
May. Forty miles east of the mountains the snow-fall is much 
increased, but during the depth of winter rarely exceeds two 
feet in depth. From the prairies the snow evaporates rapidly, 
and excepting in hollows where it drifts, it never accumulates ; 
but in the woods, where protected, it often reaches the depth 
of three to four feet towards spring. 
During the steady cold of the winter the ground freezes 
to a considerable depth, especially in seasons when there is 
a small fall of snow. Thus at Edmonton the limit of the 
frozen soil was found on the 5th of March 1858 to be at the 
depth of nearly seven feet; and in the same spot in the year 
following, on the 16th of March, it was marked at six feet. 
Regular observations were taken during both winters, and 
also when travelling in the plains, for the purpose of ascer- | 
taining the temperature of the soil at the depth of two or three 
feet, according to the method suggested by Dr Hooker. The 
following table gives the means of these observations :— 
