A more important form of lantern is the subject of the next diagram
(Fig. 2), which shows a suspended globe lantern in which there is an
attempt made to heat the air by the waste heat of the products of
combustion. It will be perceived by the diagram that a globe lantern is
furnished with a double chimney; the annular space, C, between the
inner and outer chimneys allowing for the access of air in a downward
direction. At the lower of this annular channel are the tubes D,
protected by the graduated mesh, E, and which admit the air to the
burner below. The products of combustion of the flame rise through the
inner chimney, passing around the tubes, and thereby giving up some of
their heat to the incoming air. Farther up, the chimney is partly filled
with the convoluted gas-pipe, A, which also takes up some of the waste
heat, and delivers the gas to the burner at a correspondingly high
temperature. A very simple method of lighting this burner, which in
itself does not present anything remarkable, is arranged at the lower
part of the globe, where a hole is cut and a loose conical glass plug
(which can, of course, be made to partake of the general ornamentation
of the globe) may be pushed up to allow of the passage of the lighting
agent, and is then dropped in its place again. Formal tests of the
performances of these burners are not available; and the same may be
said of the heating burners which are shown in the following diagrams.

[Illustration: FIG. 3.]

The first of these (Fig. 3) is called by Mr. Defty a "pyramid heater,"
and is designed to heat the mixture of air and gas before ignition, by
conduction from its own flame. The inventor claims to effect a perfect
combustion in this manner with considerable economy of fuel. It is
evident, however, that a good deal of the gas consumed goes to heat the
burner itself.