Fig. 12. Rjukan-fos Saltpeter Works. The water is carried from the upper power house to the lower through a tunnel just within the walls of the cliff. The current from both power houses will be brought to this building, in which will be utilized more electric power than any single plant in the world.
must be sold under a guarantee of 99.5 per cent purity, but all the recent shipments I was told were 99.98 per cent. pure. Sodium nitrite is also manufactured, which is very extensively used in the color-works of Germany, and apparatus is being installed to immediately increase the amount produced.
At present in this plant 40,000 horse power are used, brought down from the Svaelgfos on the Tinelv, while farther down the same stream and in the outskirts of Notodden the Tinfos, with a fall of 65 feet, is utilized for pulp mills. Between these two falls on the Tinelv is another, the Lienfos, and here a dam is nearly completed which will furnish an additional 15,000 horse power to the Notodden works.
As soon as the success of the nitrate factory at Notodden was assured measures were taken to utilize the water of the Rjukanfos, higher up on the same watershed. This fall, though rather inaccessible, has long been considered one of the finest in Norway. The water plunges down more than 1,600 feet, almost 800 feet of this being in a single drop. Below the fall the stream is a mass of rapids for several miles before it reaches the beautiful Tinsjö, a "finger lake," some twenty miles long and perhaps two broad in its widest portion.
The engineering problem at the Rjukanfos was by no means simple, but is being solved by bringing the water down in two steps. From the top of the fall the water is carried in a tunnel and by open canal to a point above the upper works, which are near the foot of the fall, but