SECTION IV. 1883. ETS TRANS. Roy. Soc. CANADA. 
VIII.— The Causes of the Fertility of the Land in the Canadian North- West Territories. 
By Rosert Ben, MD, LL.D., C.E., Asst. Dir. Geol. Sur. of Canada. 
(Read May 23, 1883.) 
In all countries, except perhaps the Polar regions, the surface of the ground is over- 
spread with a greater or less thickness of soil, which differs from the subsoil in containing 
more organic matter, and generally also, in the greater fineness of its constituents. The 
fertility of the soils of different regions, and even their modes of formation, depend on a 
variety of causes and circumstances, which as yet do not appear to have been very 
thoroughly understood by geologists. The present paper is intended to point out some of 
the causes of fertility of the lands in our North-West Territories, which are necessarily 
connected with the history of their origin and formation. 
In any part of Canada where the subsoil consists of boulder-clay, coarse sand or pure 
gravel, which last is found over a large area in western Ontario, and for which I 
suggested the name of Artemesia gravel, we may see that there is a gradual fining of 
the particles towards the surface. In such cases, the main cause of this has been 
the washing of water receding from a higher to a lower level, by which each part in 
succession became, for a time the beach, along the upper line of which the finer materials 
were left. This process has since been supplemented by the frosts of winter, the heats and 
moisture of summer, the decaying agencies of time, by the shaking of the soil among the 
roots of trees whose trunks were swayed by the winds, and also by tremulous motions 
due to other causes. 
Not only does the soil become finer in texture in approaching the surface, but the 
colour increases, until, in the case of our virgin soils, it becomes nearly black at the top. 
The introduction of the carbonaceous matter to which this is due has been, to a small 
extent, owing to the decay of roots penetrating the soil, but principally to the work of 
worms, insects and other small animals of various kinds in covering over, with the earth 
brought up from their burrows, the plants which in autumn wither to the ground, and 
the leaves which fall upon it from the trees and shrubs. For without this burying process 
the substances of these plants and leaves could not, in most cases, become incorporated 
with the soil, or only to the very small extent which would be due to the mineral matter 
contained in their tissues. 
Where a soil is deep enough, its fertility is chiefly due to the proportion of organic 
matter which it contains. This organic matter cannot be long retained without a sufficient 
depth of the soft inorganic material, and the more finely the latter is divided the more 
permanently will the soil retain the former. It has often happened in this country, 
that on clearing off the forest, the original soil, resting on rock or coarse sand, was extra- 
ordinarily fertile, but after a few years of cultivation, has disappeared almost entirely or 
become greatly reduced in quantity, and almost sterile. Bush-fires burning with great 
intensity have swept over large tracts of the coniferous forests of the northern parts of 
