solution, a few seconds after lighting, affords a focus of white light
remarkable for its steadiness and brilliancy. A draught of air is
created by a jet of gas issuing from the hollow needle, B, and passing
through the vessel, D, which is provided with orifices, O, for the
entrance of air. The air and gas pass from D into C, whence (after
their intimate mixture is effected) they pass into the tubular
arrangement, F, at the top of which combustion takes place.

To regulate the proportions in which the air and gas should mingle, in
order that the combination should be as intimate as possible, the air
inlet is made variable by a perforated collar, which permits of the
orifices, O, being more or less covered. The other proportions of the
burner--that is to say, the relative capacity of the two compartments
and the length of the hollow needle--are determined by the sectional
area of the supply-pipe for the gas, which is admitted under moderate
pressure. Instead of a wire-gauze cap, impregnated with a solution of
metals or of salts, two fine platinum wires may be used--one bent into
the form of a semicircle of about an inch radius, and the other (of
slightly larger diameter) rolled spirally round the former. When both
ends of the two wires are connected with the upper portion of the
tubular arrangement (which in this case is flattened), and the gas is
ignited at the burner, the metallic arc becomes red hot, and then
brightly incandescent, emitting a light, less brilliant indeed than
with magnesia, but of remarkable steadiness.

In this case the production of light is chiefly due to the fact that
calorific condensation, caused by the use of the helicoidal coil
surrounding the curved wire, prevents loss of heat in this conductor.
In these forms of high-power burner, in which the gas is used directly
for the production of light, the difficulty generally encountered of