Acetylene

Artificial Lighting:
In 1892 it was discovered that lime and coal fused together in the intense heat of the electric furnace formed a crystalline, metallic-looking substance called calcium carbide. As a result of that discovery, this substance was soon made on a large scale and sold at a moderate price. The cheapness of calcium carbide has made it possible for the isolated farmhouse to discard oil lamps and to have a private gas system. When the hard, gray crystals of calcium carbide are put in water, they give off acetylene, a colorless gas which burns with a brilliant white flame. If bits of calcium carbide are dropped into a test tube containing water, bubbles of gas will be seen to form and escape into the air, and the escaping gas may be ignited by a burning match held near the mouth of the test tube. When chemical action between the water and carbide has ceased, and gas bubbles have stopped forming, slaked lime is all that is left of the dark gray crystals which were put into the water.

When calcium carbide is used as a source of illumination, the crystals are mechanically dropped into a tank containing water, and the gas generated is automatically collected in a small sliding tank, whence it passes through pipes to the various rooms. The slaked lime, formed while the gas was generated, collects at the bottom of the tanks and is removed from time to time.

The cost of an acetylene generator is about $50 for a small house, and the cost of maintenance is not more than that of lamps. The generator does not require filling oftener than once a week, and the labor is less than that required for oil lamps. In a house in which there were twenty burners, the tanks were filled with water and carbide but once a fortnight. Acetylene is seldom used in large cities, but it is very widely used in small communities and is particularly convenient in more or less remote summer residences.

Electric Lights.
The most recent and the most convenient lighting is that obtained by electricity. A fine, hairlike filament within a glass bulb is raised to incandescence by the heat of an electric current. This form of illumination will be considered in connection with electricity.