THE LAURENTIAN PLATEAU.—The general characteristics of the Laurentian region have already been described, and it remains to trace their effect upon its economic development. The great shield of Archaean rocks, of which those known as Laurentian are the most widely distributed, although others called Huronian and Keewatin occur in many places, weathers down into a poor and infertile soil. From the upper parts of the plateau much of this soil was removed by the glacial ice-sheet, and in many places the bare ice-polished rocks still appear on the surface. In the valleys the soil is fre quently much deeper, but it is only along the river courses, where the debris from the rocks has been resorted by river action and mixed with sediment, that it is really fertile. An exception to this general statement ought to be made, however, in favour of these localities, for example, along the west coast of Hudson Bay, where inliers of younger rocks have weathered down into a much better soil.
To these unfavourable conditions of soil must be added conditions of climate equally unfavourable. The greater part of the whole region has a summer temperature too low for successful agriculture, and it is only in the more southerly parts that cultivation is ever likely to be profitable. With the development of the mineral resources of the region, and the consequent opening up of its com munications, it is quite probable that numerous small agricultural communities may ultimately settle in favoured localities. These will probably have recourse to mixed farming, but, although they will meet a gradually growing local demand, they are hardly likely ever to affect the world's supply of agricultural produce.
To the south of lines connecting the Seven Islands, in the Gulf of St. Lawrence, with the southern part of James Bay, and the mouth of the Albany with the Lake of the Woods, the Laurentian area is covered with trees of the Northern Pine Belt, and this is one of the great lumbering districts of Canada. The multitude of rivers, the hard winters, and the spring floods, all facilitate the movement of the timber from the forest ; while the falls, which occur on the margin of the plateau, provide water-power for saw mills. In this region, also, and for somewhat similar reasons, the manufacture of wood pulp has become of considerable importance. Among the chief centres of the industry are the districts round Chicoutimi, near Lake St. John, where water-power is abundant,
Sturgeon Falls on Lake Nipissing, and Hull, Buckingham, Lachute, and Sault Ste. Marie, all on the margin of the Laurentian Plateau.
Although only relatively small areas of the Laurentian Plateau have as yet been carefully prospected, the mineral wealth of the region would seem to constitute its chief claim to economic im portance. It is found mainly in those districts in which rocks of the Huronian, Keewatin, and Hastings-Grenville formations prevail, although it also occurs along with intrusive igneous rocks. Of these various formations there are considerable areas in the south, and they are also believed to occur in other parts of the plateau.
The most important minerals obtained from the region under consideration are copper, silver, and nickel. The first of these is found chiefly in the nickel-copper mines at Sudbury, which, although previously known, were not regarded as of much importance until attention was drawn to them in 1883. Since then they have been extensively worked, and in 1911 produced about 17,000 tons of nickel and 9,000 tons of copper. The Sudbury mines, along with those of New Caledonia, practically produce the world's supply of nickel. Copper is also found along the north shores of Georgian Bay, following the line of the Canadian Pacific Railway, but the output is as yet of little importance. In 1903 extensive deposits of silver were found at Cobalt, about 100 miles north-east of Sudbury, and within the last few years the production of this region has greatly increased, the yield for 1911 being 30,000,000 ounces. Along with the silver, cobalt and nickel are also found, the former in such quantities indeed that it is unsaleable. Iron ores occur in various parts of the Laurentian region, but have not been worked to any great extent. The largest output is at the Helen mine in Michipicoten, which in 1911 produced 230,000 tons. Considerable quantities of good iron ore are said to exist in Ungava, and it has been suggested that power to work them might be obtained from the Grand Falls on the Hamilton River.
Although great interest is at present being taken in the Laurentian Plateau, and more especially in its southern parts, geographical conditions decree that it will remain a mining and lumbering rather than become an agricultural country.