162 R. BELL ON THE FERTILITY OF LAND IN THE NORTH-WEST. 
just been described, is the fact that the moles, and all the other animals which have been 
mentioned, are most active in their labors in the autumn, say, from the early part of Sep- 
tember until the hard frost sets in, or during the period when the grass and other prairie- 
plants have matured and contain in their tissues the maximum amount of substance. 
During the spring and summer they appear to have little inclination to burrow, their 
attention being occupied with raising their families or other matters, but after the begin- 
ning of September they all become very busy, as if they were deeply impressed with the 
necessity of digging a great many holes in the ground. It is astonishing how many bur- 
rows each individual of these different kinds of animals will dig. In most cases it is diffi- 
cult to perceive what benefit the creature itself can derive from this promiscuous digging 
of a multitude of burrows. At this busy season the animals themselves are in the best 
condition, food being easily obtained, and it really seems as if the object of the energy 
and activity which they then display were mainly for the purpose of turning over, deep- 
ening and enriching the soil. Darwin has shown conclusively that the work which may 
be accomplished by earth-worms, even in a comparatively short period, is enormous, but 
their labors are slow compared with those of the moles, gophers, spermophiles and badgers. 
During the summer months, the surface of the ground in the North-West becomes 
heated in the day-time, but this season is of comparatively short duration, and the heat 
does not penetrate deeply, so that even in the warmest season the average temperature of 
the soil a short distance below the surface is low, as was demonstrated by Captain Pal- 
liser’s series of observations ; while it is frozen solid for about five months of the year. This 
tends to preserve the organic matter, on which, with sufficient moisture, its fertility mainly 
depends, since the precise chemical composition and proportions of the commoner inorganic 
constituents do not seem to be of much consequence in this connection. The soils of the 
North-West are, however, rich in phosphates and sulphates, in lime and in potash. 
Although the region which has been spoken of extends through eleven or twelve 
degrees of latitude, its climate is pretty uniform throughout. I have described what I 
consider to be the fundamental and also the immediate or direct causes of the fertility of 
its soil, but perhaps the remote cause, is to be looked for in its northern situation. It is 
the sufficiently cool and moist climate (as compared with the arid regions of the south) 
that produces the rich growth of grasses, the repeated burial of which year after year, as 
we have seen, enriches the land. It also allows of the existence of the insects, roots, etc. 
the food of the animals which perform this work, and finally it prevents the rapid decay 
and disappearance of the fertilizing organic matter after it has become incorporated in the 
soil. We can thus trace a mutual dependence of those circumstances which together have 
given to our North-West territory that surpassing fertility of soil, which will attract to it 
a vast population, notwithstanding its present distance and the severity of its winters. 
If the fertility of tens of millions of acres of land in the North-West, and conse- 
quently their value, have been mainly due to the work of moles, these apparently insigni- 
ficant little creatures may be regarded as the most important of the native animals of the 
country. The condition of the soil of the North-West, resulting from the processes which 
have been described, is not without its geological interest, since it shews that the prairies 
must have existed for a great length of time. Various other facts also tend to prove this, 
and, indeed, it is doubtful if the forests of modern geological times ever extended much 
beyond their present limits. 
