630 THE FRESH-WATER LOCHS OF SCOTLAND honour of Louis Agassiz, and must have covered an area of about 110,000 square miles, exceeding the combined areas of the present Laurentian lakes. It discharged southward to the Mississippi, and excavated the channel now occupied by Lake Traverse, Big Stone Lake, and the Minnesota River; but as the glacier retreated, and an outlet northward was opened up, the level of the waters was gradually reduced till the lakes of to-day were left in the deepest portions of its basin. This great lake, as measured from its shore-lines, had a diameter from north to south of 675 miles, and from east to west of about 300 miles, and had a drainage area of about half a million square miles. At the site of Lake Winnipeg the ancient lake was 600 feet deep. As with the Laurentian glacial lakes, the shore-lines of Lake Agassiz now rise northward at a slight inclination, proving that an elevation of the land must have taken place during the rise and dis- appearance of the ice-sheet. Lake of the Woods is the main hydrographical feature of the country between Lake Superior and Lake Winnipeg, a district studded with lakes and intersected by swift-flowing streams. It is 70 miles long, by 60 miles broad, but its outline is indented to an extraordinary degree, and its northern portion is filled with islands. The Lake of the Woods lies about 1060 feet above sea-level, and the water area is given as 1500 square miles. Its main tributary is Rainy River, which flows from Rainy Lake, and its outflow is by Winnipeg River to Lake Winnipeg; there are many rapids in the course of Winnipeg River, which is about 163 miles long. Lake Winnipeg is about 700 feet above sea-level, 250 miles long by 60 miles broad, and has an area of about 9000 square miles; its maximum depth is about 90 feet. On the north-west it receives the waters of the Saskatchewan, together with the surplus waters of Lakes Winnipegosis and Manitoba. On the east it receives the Winnipeg, and on the south the Red River and its tributary, the Assiniboine; the Red River carries to Lake Winnipeg the tribute of Lake Traverse, situated on the Minnesota-Dakota boundary, at the southern limit of the country formerly flooded by Lake Agassiz, and drains through narrow channels sunk in the sediments of the former lake. Between the streams there are broad, nearly level inter-stream spaces, forming typical examples of new land-areas, on which shallow ponds form during rainy seasons. ' Lake Winnipeg discharges north- wards by the Nelson River through several small lakes into Hudson Bay. Lake Manitoba lies 810 feet above sea-level, and is connected with Lake Winnipeg by the Dauphin River and through St Martin's Lake. It is about 120 miles long, from 5 to 30 miles wide, and covers an area of 1850 square miles. It is a shallow lake with low shores, and very swampy at the southern end, the average depth being 12 feet.