644 THE FRESH-WATER LOCHS OF SCOTLAND applies. The remainder is a narrow valley, 5½ miles long, directed approximately north-east and south-west, called Lake Wairaumoana, which is connected to Lake Waikaremoana by a passage half a mile in width, known as the Straits of Manaia. The area of Lake Waikaremoana is about 15 square miles, and of Lake Wairaumoana about 6 square miles. The greatest depth recorded in the whole lake is one of 846 feet in Lake Waikaremoana, and occurs within a depres- sion having an area of 1·3 square miles exceeding 800 feet in depth. The deepest sounding taken in Lake Wairaumoana is 375 feet. The mean depth of Lake Waikaremoana is 397 feet, or 47 per cent, of the maximum depth; the mean depth of Lake Wairaumoana is 175 feet, or 49 per cent. Lucas considers these lakes a system of radiating valleys, having the deepest part at the point where all the valleys meet. Lake Wakatipu is drained by the Kawarau River, a tributary of the Clutha River, in South Island, and lies at a height of 1016 feet above sea-level, extending from lat. 44° 50' to 45° 20' S., and from long. 168° 20' to 168° 43' E. The two ends of the lake trend in a direction almost north and south, but the middle part runs nearly east and west. The length is 49 miles, the greatest breadth about 3 miles, and the area exceeds 112 square miles. The maximum depth obtained by Lucas was 1242 feet; the volume of water is 15 cubic miles, and the mean depth 707 feet. The lake appears to be a mountain valley filled with water. The Clutha River takes its rise in the two lakes Wanaka (area 75 square miles) and Hawea (area 48 square miles), in which maxi- mum depths of 1085 and 1285 feet respectively have been reported. Lake Manapouri, 597 feet above the sea, extends from lat. 45° 27' to 45° 35' S., and from long. 167° 28' to 167° 40' E. It is very complicated in outline, and covers an area of about 56 square miles. The greatest depth, 1458 feet, occurred within a large depres- sion about 2½ square miles in area, which exceeds 1400 feet in depth, the mean depth being 328 feet. The surface of the water lies at approximately 597 feet above sea-level. The lake receives from the north the surplus waters of Lake Te Anau (36 miles in length and 1 to 6 miles in breath), and drains south by the Waiau into the South Pacific Ocean. CRATER LAKES Crater lakes would appear to constitute a class by themselves, since they are not directly connected with river drainage, and are to a very small extent influenced by climatic oscillations. They occupv the hollows in the summits of the cones of dormant volcanoes, and the.