The unexploited sources are still enormous, over 1 o million horsepower, and the people are fully aware of this source of natural wealth. Its development becomes easier on account of the numer ous rapids and falls which characterize the rivers. As Norway also fully realizes the financial value of her remarkable scenery and of her anglers' haunts, the mode of utilizing this smokeless power in the industrialization of any area will be given much thought. A limiting factor in the "white coal" schemes is the seasonal character of many Norwegian streams which run low in winter on the freezing of their upper courses and rise rapidly during the period of maximum rainfall—here the lakes are of supreme value as safety-valves controlling spring thaw-water and autumnal rain water. Nevertheless, disastrous floods are not un known. The lakes themselves in the north and interior freeze for varying periods each year, but in the south, where the majority of the large lakes are situated, it is only during very severe winters that these reservoirs become icebound. In a land where rivers
possess so many and so varied interests selection becomes difficult.
The principal river of Norway is the Glommen, about 400 m. long, which rises about 2,300 ft. above sea-level in the highlands south of Trondhjem fjord. It is a swift stream with numerous falls, and even within 8 m. of its mouth, in Oslo fjord, there is a series of seven falls of which Sarpsfos (6o ft. high and 164 ft. wide) is the best known. The river, which runs mainly north to south, drains about 16,000 sq.m., pierces the richest timber area and provides an important railway route from Oslo to Trond hjem. Above oieren (area 36 sq.m.) the largest lake of the numer ous ones in its course, the Glommen makes a remarkable bend (at Kongsvinger). Here, in post-glacial times, the river which formerly ran due south to Vaner lake (Sweden) made a sudden swing to the west capturing the upper waters of the Laagen, for merly an independent stream. (The old bed still carries occa sional flood water from the Glommen to the lake.) The Laagen, 200 m. long, has, for a Norwegian river, a large upper basin re ceiving water from the Jotunheim and the Dovre fjeld. Its sources lie near Romsdals fjord, for which it is providing the following railway route direct from Oslo : along its lower course (River Vormen) past the shores of Lake Mjosen up the Gud brandsdal, over the water parting and down Romsdal—another railway line links Trondhjem with the head of Gudbrandsdal. This last name illustrates a common practice, in Norway, of using different names for a river in its different courses, and different names for a river and for its enclosing valley—the valley name being also frequently employed for surrounding districts. Of the other important streams entering Oslo fjord, the Tistedalelv reaches its eastern seaboard after draining through a series of long, narrow lakes connected by rapids; the Dramselv (Drammen), a large river with a considerable basin extending into Hemsdals fjeld, Valdres and File fjeld, enters on the western sea-board. Its upper tributaries, the Randselv and the Aadalselv (plunging over Honefos), unite to form the Storelv which expands into the Tyri fjord lake. Below this the real Dramselv begins and receives, on the right bank, the Hallingsdalelv which flows through Lake Kroderen—all these valleyways afford important but not easy routes, and, though the rivers are not navigable for any long stretches yet steamers are employed on the lakes. Numerous streams drain southwards from the plateau and lake district of Hardarger Vidda, one of these, the Numedalslaagen (nearly 200 M.) is noted for its falls, e.g., Hammerfos and Labrofos, and for its wealth in salmon. From the Telemarken district, runs the Skienelv (15o m.) flowing through the very deep Tinsjon and the slightly larger, deep Nordsjon ; the former lake receives the river Maane, on which is the famous Rjukanfos (415 ft. high).