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 valve in the pipe; but this arrangement may be used without any previous heating of the gas and air.

Fig. 4 shows a similar arrangement to that above described, but reversed; the gas and air being previously heated by the products of combustion. The two pipes, D, lead the gas to the burner; and the incandescent sheet of flame is drawn over a white refractory substance, having in its center an orifice through which the hot gases rise to the upper portion of the burner. The luminous sheet is spread out all the better on account of this return of the flames, which also causes the mixture of air and gas to be more complete than when they rise directly. The gas escapes horizontally from the orifices of the annular burner, B, and mingles with the double current of hot air which rushes in above the flame inside the globe, and also below through the central portion of the burner.

This lamp throws its light vertically downward; and its illuminating power may be increased by providing, above the incandescent sheet, a reflector, which diverts into a useful direction the rays thrown toward the ceiling. In this arrangement of lamp the flame is excessively condensed by its being turned back over the refractory guide; and this condensation greatly favors the production of light. On the other hand, the combustion of the gas is very perfect, because the currents of hot air are thrown directly upon the two sides of the flame; and thus the reciprocal action becomes more intense. Lastly, the division of the gas into a large number of small jets, in contact with which the hot air forms an intimate mixture, causes a greater quantity of molecules to partake in the combinations; thus affording a proportionate increase of temperature in a given space and time.

FIG. 5.

Owing to these various circumstances, the final effective duty of this burner is advantageous, so that it yields an illuminating power which may be put at from 200 to 250 per cent. above that of ordinary burners, and about 25 per cent. more than that of other regenerative burners. The flame is comparatively steady; the loss due to the friction over the white porcelain being almost eliminated, because the flame only presses upon the guide for a small portion of its surface, and is only spread out to the extent of its dark zone.

The contact between the incandescent sheet of flame and the guide may be made as short as desired, and the motion of the gaseous mass be directed by a simple button placed in the center of the burner; thus giving the form shown by Fig. 5, which, however, differs from the previous figure in the fact that the inverted flame is directed outward instead of inward.

In this arrangement the button, T, is fixed in the middle of the burner, which is made cylindrical and annular, or may consist of a ring of small tubes, to which the gas is led by a single pipe; leaving the whole "furnace" free for the circulation of air and the products of combustion. This is the most recent development of the principle patented by M. Somzee in 1882, viz., the formation of an illuminating sheet of flame, spread out laterally, while heating the gas and air by the products of combustion.

Figs. 6 and 7 show two forms of burner designed especially to give economical results with a small consumption of gas. The former is an ordinary Argand burner in which hot air is introduced into the upper portion of the flame, so as to increase the activity of combustion. The luminous sheet of flame is then spread out by a metal disk attached to the end of the tube, D, which introduces the air into the flame. The outer air becomes heated in its passage through the wire gauze, T, which absorbs the heat liberated in the interior of the apparatus, and also that which is radiated from the incandescent sheet and reflected by a metal shield, P, surrounding the dark part of the flame.

FIG. 6. and FIG. 7.

It is the combustion of gas, without the production of useful luminous effect inside the shield, which supplies the reflected as well as radiated heat to the air. The temperature is still further increased by the heat transmitted to the metal portion of the burner, and absorbed by the wire gauze, between the close meshes of which the air from outside is forced to circulate. Air is admitted inside the flame by the chimney, D, placed above the focus, and in which it is raised to a high temperature by friction on the upper part of the lamp glass, at E, and afterward by its passage through the horizontal portion of the bent tube. This tube is impinged upon on the outside by the flames, and also by the products of combustion, so that it forms a veritable heater of the currents which traverse it.

The introduction of hot air into the central portion of the sheet of flame is advantageously supplemented by the spreading out of the flame by means of the metal disk, without any possibility of its being divided. In this way a more intense heat is obtained, and consequently the illuminating power is considerably increased, by the uncombined carbon being more readily set free, and being thus kept longer in the flame, F. This burner, which may be constructed for a moderate gas consumption, gives remarkable results as regards illuminating power and steadiness; the abstraction of heat in no way impairing the luminosity of the flame, which preserves all its brightness.