FERTILITY OF LAND IN THE NORTH-WEST. 159 
Now I purpose endeavouring to answer the question: What is the cause, or what are 
the causes of the notable fertility of these north-western lands ? 
In reply, I should say that the primary cause is the abundance of the raw material 
(so to speak) for the formation of a finished soil, derived during the Drift period from the 
wide-spreading soft Cretaceous rocks, which are almost coéxtensive with the fertile area. 
The Drift from the northward and eastward brought with it large quantities of sand and 
eravel, which became mingled with the Cretaceous marls, and so formed an excellent 
material out of which the soil has been developed. The first step in its elaboration has been 
the modifying influence of water, which, however, was only of a transient nature over 
the greater part of the area; and while its effects on the surface, with its endless different 
levels, may be everywhere seen, it did not remain long enough to deposit extensive beds 
of sand, silt or clay, except on the lowest prairie steppe, already referred to, and over certain 
tracts, at greater altitudes, where the original surface appears to have been sufficiently 
even and level to receive deposits of considerable extent. 
Having the favourable crude material for the production of a good soil, we come now 
to consider the agencies by which it has been finally reduced to its present almost uniform 
and rich loamy character. Some travellers have asserted that the dark colour of the deep 
soil of the North-West is due to the carbon left on the surface by the prairie-fires, and that 
the so-called alkali of the ponds is derived from the ashes of the grass washed down into 
the hollows by the rain. Neither of these ideas is correct. The carbon left by the occa- 
sional burning of the prairies in dry seasons, although for a time rendering the landscape 
black and hideous, is really exceedingly small in amount, and is so light and finely 
divided that it soon vanishes. Again, carbon alone would not fertilize the soil, and it 
would impart to it a character different from what we actually find. The salts found in 
the ponds do not consist of carbonate of potash at all, but principally of sulphates and 
chlorides of sodium, magnesium and lime, derived from the Cretaceous marls, out of which 
the subsoil is so largely formed. 
Darwin has proved that in England and some other parts of the world, earth-worms 
have played an important part—in fact the chief part—in the formation of the vegetable 
mould in those countries, which, he says, might be more appropriately called the animal 
mould. “The uniform fineness of the particles of which it is composed is one of its chief 
characteristic features.” The black vegetable mould of the North-West is comparatively fine 
and uniform in texture, but as already mentioned, some gravel and small stones are found 
mixed throughout it, so that in this respect it differs from the mould formed by earth-worms, 
As far as I am aware, earth-worms are not found in the North-West. If they exist at 
all, it will be in the woods, or in the older cultivated lands into which they may have been 
introduced from abroad, as I have never seen them nor heard of them in the unbroken 
prairie. The apparent absence of these creatures in the soil of the north-western prairies 
may be due to a variety of circumstances. The summers may be occasionally too dry for 
them to endure, or if they once existed when the country, as some suppose, was wooded, the 
prairie-fires may have killed them off, first from one area and then another, until the whole 
race has disappeared. But the most probable cause of their absence is the intensity and 
long continuance of the frost in winter. It seems that earth-worms cannot live where the 
frost penetrates below the depth to which they can burrow ; and this is certainly the case 
in our open prairies, although probably not in the wooded areas. 
