Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/577

This page needs to be proofread.


geography]

CANADA

Cambrian, and holding numerous and important veins of auriferous quartz, characterize its Atlantic or south-eastern side, while valuable coal-fields occur in Cape Breton and on parts of its shores on the Gulf of St Lawrence. In New Brunswick the Carboniferous rocks occupy a large area, but the coal seams so far developed are thin and unimportant. Metalliferous ores of various kinds occur both in Nova Scotia and in this province, but with the exception of the gold already mentioned, have not yet become the objects of important industries. Copper and asbestos are the principal mineral products of that part of Quebec included in the region now under description, although many other minerals are known and already worked to some extent. Extensive tracts of good arable land exist in many parts of the Acadian region. Its

527

surface was originally almost entirely wooded, and the products of the forest still continue to hold a prominent place. Prince Edward Island, the smallest province of Canada, is low and undulating, based on Permo-Carboniferous and Triassic rocks affording a red and very fertile soil, much of which is under cultivation. The St Lawrence Plain.—The lowlands or plain of the St Lawrence valley, extending from the vicinity of the city of Quebec to Lake Huron, with an extreme length of over 600 miles, constitute the greatest connected spread of arable land in Eastern Canada, included partly in the province of Quebec and partly in Ontario, with a total area of some 38,000 square miles. This fertile region, bounded to the south-east by the Notre Dame ranges already referred to, is limited on the south, farther west, by the St

Oxford i go i.

B. V.Darbnhirt 6- O.J.B. Howarth Map of Canada. Lawrence river and Lakes Ontario and Erie. To the north it ends along the base of the Laurentian plateau. As its uniform topographical features would indicate, it is underlain by nearly horizontal and undisturbed rocks. These range in age from Ordovician to Devonian (the latter chiefly developed in the peninsular part of Ontario), and are mainly limestones. Superposed on these rocks, the eastern part of this plain, to a line which may be drawn some distance west of Ottawa, are marine clays and sands of Pleistocene age. Farther west these are replaced by similar deposits of the same period, but without evidence of marine origin. Petroleum and natural gas occur in the rocks underlying this plain in Ontario, but metalliferous deposits are almost wanting. The continuing wealth of this region lies in its fertile soil, and within its area the largest and oldest centres of population are situated. The greater part of the length of Lake Huron and the whole northern margin of Lake Superior bathe the foot of the Laurentian plateau, which rises directly from these lakes. Continuing westward from Thunder Bay, on Lake Superior, a great southern spur of this plateau is crossed, after which

we reach the eastern edge of the interior continental plain. The Interior Continental Plain.—This plain runs northwestward between the border of the Laurentian plateau and the line of the Bocky Mountains. It includes part of Manitoba, the whole of Assiniboia, and the greater portions of Saskatchewan, Alberta, and Athabasca. To the northwest it becomes narrowed and interrupted, but preserves its main physical features to the Arctic Ocean about the mouth of the Mackenzie. This great region of plain is 800 miles in width from east to west along the international boundary. Seven degrees of latitude farther north, it is still about 400 miles in width. To the south it constitutes the vast prairie region of Canada, with an aggregate area more than twice as large as that of Great Britain. North of the Saskatchewan river it becomes generally wooded, by reason of the greater humidity of the climate, but without essentially changing its physiographic features. From the vicinity of the Winnipeg group of lakes, where its elevation is about 800 feet above the sea, it rises gradually to the west or south-west until it attains an elevation of from 3000