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.