Among other inventors who have turned their attention to gas consumption is to be found Mr. H. Defty, who has made several forms both of heating and lighting burners. Mr. Defty has sought in the latter to apply the principle of heating the air and gas in a simple manner, with the object of obtaining improved photometrical results. The double-chimney Argand, as tried many years since by Dr. Frankland and others, makes a reappearance in one of Mr. Defty's models, illustrated in the accompanying diagram (Fig. 1). [Illustration: Fig. 1.] Here we have the double-chimney, a and b, for heating the air supplied to an ordinary Argand, by causing it to pass downward between the two chimneys, and inward to the point of combustion through a wire-gauze screen, c, under the inner chimney; but, in addition thereto, Mr. Defty hopes to gain an improved result by causing the gas to pass through the internal tube, s, which rises up in the middle of the flame. The gas, which enters at e, is made to pass up through the inner tube and down through the annular space to the burner. [Illustration: Fig. 2.] 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. [Illustration: FIG. 4.]