158 , NOTES ON MANITOBA. 
Having stated what the recorded facts as to rainfall are, I will 
give my reasons for asserting that these facts are but the necessary 
consequences of the physical conditions existing in the West of the 
North American Continent. 
In the early part of this paper I referred to the position of the 
Great American Desert and pointed out one of its effects on the air 
currents rising northward from the Gulf of Mexico—viz,, its power 
to attract and draw them to itself, and to the westward of their 
natural course. Another effect, now first mentioned, is that arising 
from the heat given off from the surface by radiation during the 
summer months. The Gulf air currents, laden with moisture, when 
drawn over the desert are met by the rarified and heated air ascend- 
ing from its surface, and that rainfall which in the ordinary course 
they would shower down (being prevented from falling) passes on 
and is wafted by the prevailing winds in the direction of our North- 
West, where, being removed from the effects of the desert heat, they 
give forth their long borne and priceless load in the form of our 
summer rains. 
Having shown cause for the summer rains, I may, now, state that 
the simple “‘suspension of those desert effects which gave the summer 
rains” is the cause of the almost total absence of rain in the autumn 
and winter periods. 
It was shown when writing on the winter temperature that as 
the desert cooled down the main air currents from the Gulf of 
Mexico no longer pursued a westward course but passed to the east- 
ward, This change of direction takes them over the region of the 
Canadian Lakes where they deposit that rainfall which in summer 
fell on the plains of the North-West. 
AGRICULTURAL OPERATIONS. 
The progress of the seasons and the labours of the Se 
may be summarized as follows : 
Early in April the hot and unclouded sun clears from the lands the 
last of its light snow-covering—thaws, and at the same time dries 
the ground sufficiently to fit it for the plough—and almost simul- 
taneously for seeding. Germination quickly follows and the young 
roots, moistened by the thawing of the subsoil, follow the pores 
opened out by the disintegrating power of the winter frosts, and 
penetrate to a depth inconceivable to those who have not put the 
