The electric furnace has made possible the preparation of substances unknown before, and the production in large quantities at low cost of substances that before were too costly for general use. One of the best known of these substances is aluminum. With the discovery of the electric-furnace method of extracting aluminum from its ores, the price of aluminum fell from one hundred and twenty-four dollars per pound to twelve cents per pound. Among the many uses of the electric furnace we may mention the preparation of calcium carbide, which is used in producing the acetylene light; carborundum, a substance almost as hard as diamond; and phosphorus, which is used in making the phosphorus match. It is used also to some extent in the manufacture of glass, and, in some cases, for extracting iron from its ores. The Wireless Telegraph A ship in a fog is struck by another ship. The water rushes in, puts out the fires in the boilers, the engines stop, the ship is helpless in mid-ocean in the darkness of the night. But the snapping of an electric spark is heard in one of the cabins. Soon another vessel steams alongside. The life-boats are lowered and every person is saved. The call for help had gone out over the sea in every direction for two hundred miles. Another ship had caught the signal and hastened to the rescue, and the world realized that the wireless telegraph had robbed the sea of its terrors. Without the curious combination of magnets, wires, and batteries on the first ship no signal could have been sent, and without such a combination on the second ship the signal would have passed unheeded. How was this combination discovered, and how does it work? Faraday, as we have seen, discovered the principle of the induction-coil. With the induction-coil a powerful electric spark can be produced. The friction electrical machine was known long before the time of Faraday. Franklin proved that a stroke of lightning is like a spark from an electrical machine, only more powerful. These great discoverers did not know, however, that an electric spark sends out something like light which travels in all directions. They did not know it, because they had no eyes to see this strange light.