Central Part of British North America. 221 
3000 feet, thunder storms are more rare, yet a good deal of 
rain falls. During the latter half of June 1858, there were 
nine days of rain and cloudy weather to six of fine clear sky. 
The mean temperature for the same period was 5878, from 
observations taken at sunrise, 2 P.M., and sunset, the highest 
recorded being 72°, and the lowest 46°. This excludes the 
minimum night temperature, however, which often fell within 
a few degrees of the freezing point. The mean degree of 
moisture in the atmosphere was 0°64, saturation being 100. 
During the month of July in the same year there were twelve 
days of cloudy sky and rain. The mean temperature was 
59°°5, the extremes recorded being 70° and 40°, with the 
degree of humidity 0-59, or rather less than in June. 
In August, in the district along the base of the mountains, 
having an altitude of nearly 4000 feet, the mean tempera- 
ture was 54°, and the extremes recorded as occurring between 
‘sunrise and sunset were 79° and 40°5. Almost every night, 
however, we found that ice formed in the kettles, and that 
the ground was covered with hoar-frost. 
The radiation, as might be expected, is very great during 
the summer nights in the northern prairies, so that when 
the sky is clear the quantity of dew that forms is great in 
proportion to the degree. of moisture in the atmosphere. It 
is owing to this, combined with the sharp frosts in August 
and September, which arrest the sap before the grasses have 
fully flowered and faded, that the rich pasture along the 
North Saskatchewan plains is preserved green and juicy until 
the snow falls, after which the hard steady winter keeps it 
fresh and nutritious as artificial hay until the return of 
spring. Along the South Saskatchewan the country is arid, 
and without such pasture; but in travelling in that region, no 
marked difference was observed in the frequency of rain- 
clouds during the summer than when further to the north ; 
and that a considerable amount of moisture passes over these 
plains is proved by the marked increase in the vigour of the 
vegetation on the high and isolated patches of table-land 
which are scattered over the arid country. It is probable 
that the prevalence of a hard clay soil, formed from the 
cretaceous strata, which bakes under the heat of the sun from 
NEW SERIES,—YOL. XIV. NO. 11.—ocT. 1861. 25 
