The general outline of the north of the {71} continent of America, and at any rate the vast distance to be traversed to reach the Pacific from the Atlantic, could now be surmised with some accuracy. But the internal geography of the continent still contained an unsolved mystery. It was known that vast bodies of fresh water far beyond the basin of the Saskatchewan and the Columbia emptied towards the north. Hearne had revealed the existence of the Great Slave Lake, and the advance of daring fur-traders into the north had brought some knowledge of the great stream called the Peace, which rises far in the mountains of the west, and joins its waters to Lake Athabaska. It was known that this river after issuing from the Athabaska Lake moved onwards, as a new river, in a vast flood towards the north, carrying with it the tribute of uncounted streams. These rivers did not flow into the Pacific. Nor could so great a volume of water make its way to the sea through the shallow torrent of the Coppermine or the rivers that flowed north-eastward over the barren grounds. There must exist somewhere a mighty river of the north running to the frozen seas. It fell to the lot of Alexander Mackenzie to find the solution of this problem. The {72} circumstances which led to his famous journey arose out of the progress of the fur trade and its extension into the Far West. The British possession of Canada in 1760 had created a new situation. The monopoly enjoyed by the Hudson's Bay Company was rudely disturbed. Enterprising British traders from Montreal, passing up the Great Lakes, made their way to the valley of the Saskatchewan and, whether legally or not, contrived to obtain an increasing share of the furs brought from the interior. These traders were at first divided into partnerships and small groups, but presently, for the sake of co-operation and joint defence, they combined (1787) into the powerful body known as the North-West Company, which from now on entered into desperate competition with the great corporation that had first occupied the field. The Hudson's Bay Company and its rival sought to carry their operations as far inland as possible in order to tap the supplies at their source. They penetrated the valleys of the Assiniboine, the Red, and the Saskatchewan rivers, and founded, among others, the forts which were destined to become the present cities of Winnipeg, Brandon, and Edmonton. The annals of North-West Canada during the next thirty-three years are made up of the {73} recital of the commercial rivalry, and at times the actual conflict under arms, of the two great trading companies.