heating the air (present in a larger volume than the gas) has been
successfully overcome.

Fig. 3 shows the straight and outspread flame burner with a special
heater. In this arrangement the gas and air are heated before
combustion, in the compartment, G, directly exposed to the action of a
small Bunsen burner, R, which is placed (in an opaque glass) in the
middle of a lyre-shaped figure formed by the two gas-pipes, AA. The
burner proper consists of two fine annular passages meeting above, and
emitting a thin annular sheet of gas over the guide, T, made of a
white refractory substance placed between the two annular jets. The
object of this guide is to stretch the incandescent sheet of flame,
composed of several jets, and interpose friction, so as to prevent a
too rapid ascent of hot gases.

[Illustration: FIG. 3 and FIG. 4 REGENERATIVE BURNERS WITH INVERTED
FLAMES.]

The luminous focus is placed within a glass globe, C, mounted on the
bell, B, of the heater; and the external air enters this bell,
mingling with the products of combustion of the heating burner, R. The
portion, D, of the annular passage, B, being made of a highly
conductive metal, the gas becomes heated in passing to the burner, so
that both gas and air are raised to the same temperature by the time
they reach the orifices of the burner. Instead of prolonging the
gas-pipe to the point of bifurcation, a chamber may be arranged
immediately below the guide, for the gas and air to become intimately
mixed by passing through several perforations or wire gauze, receiving
the excess of heat from the white porcelain guide. The admission of
gas to both the main and heating burners is regulated by a double