Acetylene, a set'i leen, a pure gas consisting of carbon and hydrogen. It is clear, colorless and heavy, has a distinct odor, and burns with a flame of intense brilliancy. It is present in ordinary illuminating gas only to the extent of from 1/2 to 1 1/2 per cent. The gas is poisonous to the same extent as ordinary gas, but its characteristic odor gives warning if there is any leak. There is no odor from the gas while burning, the flame being clear, white and steady, without smoke and with little heat. Acetylene gas is produced, commercially, by the action of water on calcium carbide, the result of electrical fusion of coal dust and lime in the proportion of 1130 pounds of coal dust to 1750 pounds of lime with a resultant of 2000 pounds of calcic carbide. This is a dark, gray, cinder-like substance. The calcium carbide can be exposed to the most intense heat of a blast furnace without perceptible effect. Dry air does not act upon it to any appreciable extent, although if the air is moist it reduces the gas-producing power. The instant that water is brought in contact with the carbide, acetylene gas is produced. A double change takes place. The oxygen of water unites with the calcium of the calcium carbide, forming oxide of calcium, which combines with the water, forming hydrate of calcium. The hydrogen of the water unites with the carbon of the calcium carbide, forming the acetylene, which rises and is used. For many years acetylene gas was known as a laboratory product too expensive for anything but experimental use. A possible method of producing this gas on a commercial basis was developed in the electric furnaces of the Willson Aluminium Company, Spray, N. C., by T. L. Willson and Major J. T. Morehead, president of the company, and a geologist of national reputation. In the course of certain experiments coke and lime were fused together in the electric furnace, and the resulting products were thrown into a bucket of water. The violent bubbling, caused by the gas, directed attention to it; a match was struck, and the gas burst into a clear flame. The development of the experiments resulted in large electric furnaces being built at Niagara Falls, and calcium carbide is now a commercial product, sold directly to consumers, who with small generators make their own illuminating gas. A special burner is necessary. It contains two small openings, 1 and 2, from which the gas issues and mingles with the air before it ignites at 3.