The inverted-mantle gasoline-gas lamp shown in Fig. 194, furnishes a good example of mechanism and principle of operation, when used with the hollow-wire system. This is the bracket style of lamp but the same mechanism is used in other forms of fixtures. Lamps of similar construction are suspended from the ceiling, either singly or in clusters; they are also used in portable form.

Fig. 194. - -Sectional view of hollow-wire mantle gasoline lamp.

In Fig. 194 the lamp consists of a bracket H, which is secured to the wall and through the stem of which the gasoline is conducted to the generator by the pipe W. The arrows show the course of the gasoline and its vapor as it passes through the lamp. On entering the generator the gasoline first passes, the percolation, through an asbestos wick B, the object of which is to prevent the vapor pressure from acting directly on the gasoline in the supply tube. The gasoline passes through the wick B, largely by capillary action, as it must enter the generator against a pressure greater than that afforded by the pressure tank. The vaporization of the gasoline takes place in the tube above the mantle T, from the flame of which it receives the necessary heat.

In lighting the lamp an asbestos torch saturated with alcohol is ignited and hung on the frame, so that the flame may heat the generating casting N. This process usually requires less than a minute, generally about 40 or 50 seconds. The torch supplies heat sufficient to generate the vapor for lighting the lamp, but as soon as lighted the heat from the glowing mantle keeps the generator at the required temperature for continuous supply of vapor.

When the generator is sufficiently heated by the generating torch, the needle valve N is opened by pulling the chain P. This allows the gasoline vapor from the generating tube to escape at G into the induction tube R. As the vapor enters the induction tube at a high velocity, it carries with it the atmospheric air in quantity sufficient to render it completely combustible. The opening G and the tube together form a Bunsen burner. The lamp is so proportioned as to give a mixture of gasoline vapor and air that will produce complete combustion in the mantle T. The portion of the burner Z, through which the gas enters the mantle, is a brass tip, filled with a fluted strip of German silver, so arranged that the gas on entering the mantle will be uniformly distributed and that the heat generated will render the entire mantle uniformly brilliant.

One feature of the lamp that requires special attention is the opening G, through which the vapor from the generator is discharged into the induction tube. This is a very small opening and occasionally becomes stopped or partly closed. When this occurs the lamp fails to receive the necessary amount of gas, and the light is unsatisfactory. In this lamp, the cleaning needle Q is provided for removing the stoppage. The needle is simply screwed into the opening and forces out the obstruction; when it is withdrawn, the opening is left free. A more convenient device for accomplishing the same purpose is described in the portable lamp, Figs. 195 and 196.