THE DANCING FLAME.
Make a very small gas jet, to which fit a minute burner; Sugg’s steatite pinhole burner answers best. Above the burner, at a distance of two inches, fix a seven-inch square piece of wire gauze; ordinary window-blind gauze of thirty-two meshes to the lineal inch acts perfectly. Turn the gas on, and light the flame above the gauze. Keep the room free from draught, and the flame will be steady; but at the least sound the flame is certain to move. It is a slender cone, about four inches high, the upper portion giving a bright yellow light, the base being a non-luminous blue flame. At the least noise the flame roars, sinking down to the surface of the gauze, and becoming almost invisible. It is very active in its responses, and, being rather a noisy flame, it is heard immediately. To the vowel sounds it does not appear to answer discriminately. It is extremely sensitive to A, very slightly to E, more so to I, entirely insensitive to O, but slightly sensitive to U. It dances admirably to a musical box, and is highly sensitive to most sonorous vibrations.
A jet of gas issuing through a circular orifice being lighted, and the pressure of the gas then slowly augmented by means of weights placed on the gasometer until such a pressure is reached that the jet of flame is nearly, but not quite, on the point of flaring. The flame will be about two feet long, and so sensitive to sound that a slight chirrup or a hiss from any part of the theatre will make the flame shorten itself to seven or eight inches.