226. The common fishtail, or union jet, burner is shown in Fig. 82. The gas issues from the orifices shown, in two round jets, which collide and spread out into a flat two-pointed flame, of the general shape shown at A.

Fig. 82.

Fig. 83.

227. The Batswing burner is shown in Fig. 83. The head of the tip is hemispherical, and the gas issues through a single straight slit which spreads out into a thin flat sheet of flame, of the general shape shown at B.

The capacity of these burners, in cubic feet of gas per hour, is marked either by figures stamped upon them, or by means of rings cut around them-one ring for each cubic foot. These marks serve to show the capacity only in the most general way, and cannot be relied upon for accuracy.

228. The Argand burner, shown in Fig. 84, consists of a hollow ring a, which is attached by two hollow arms b to a socket c, which is threaded to screw on an ordinary burner nipple. The gas issues from the interior of the ring through a series of small holes d, and the jets all unite to form a complete circle of flame. A plentiful supply of air passes up through perforations in the chimney holder e and also through the central hole of the burner. The volume of the gas is regulated by a screw g, which has a very coarse pitch, requiring only about one-third of a revolution to nearly close the valve h.

In order to secure the best results with this burner, the pressure should be about .2 inch of water, and the chimney f must be of such diameter and length that the draft will supply the proper amount of air to completely burn the gas-no more or less. This amount will vary somewhat with different qualities of gas.

Every Argand burner should have a volumetric regulator. Without it, they are liable to be wasteful, while if they are properly regulated and adjusted, they will burn gas very economically.

Compound Argand burners have two or more burner rings.

Fig. 84.

229. The regenerative lamp, or burner, is made in many ways, but the object in every case is to heat the air or the gas, or both, before the gas is burned.

The simplest application of the regenerative principle is shown in Fig. 85. Two or more small Bats-wing burners are supplied by a pipe which descends close to the flames and which is heated by them. The gas is thus heated before it is burned, and the temperature of the flame is augmented accordingly. Even this crude application of the principle of regeneration produces a perceptible increase in the brilliancy of the lights.

Fig. 85.

Fig. 86.

230. In the Wenham lamp, shown in Fig. 86, both the air and gas are heated before combustion. The burner a is an ordinary Argand ring inverted; that is, having the jets of flame upon the bottom end. The flames b are turned outwards by a deflector c, and theycurveover the rounded surface of porcelain rings d, thus forming a broad horizontal ring of flame of great brilliancy. The lamp is closed tightly against the entrance of air below the flame by means of the glass hemisphere g. The hot products of combustion pass upwards around the tube e through a number of tubes f, and up the chimney h. The gas passing down the tube k is highly heated before it reaches the burner. The air required for combustion enters between the cap m and the shell n, passes between the hot tubes f, and thence downwards through the tube e to the Argand burner. This construction is said to increase the amount of light given off from three to four times above that produced by good Batswing burners using the same quantity of gas.

Fig. 87.

231. The incandescent lamp is made in various ways by different inventors, but all of them operate on the same general plan. The Wels-bacli lamp, shown in Fig. 87, is a good representative of the class. The burner is of the ordinary Bunsen variety (see Art. 234); the gas enters at a and the air at i. The mixture burns on the top of the wire gauze cover b, producing great heat and but little light. This heat is transformed into light by means of a hollow tubular network c, which is suspended over and around the burner by a wire support d. This network, or mantle, is composed of threads of incombustible material, which becomes brilliantly incandescent when highly heated, and thus converts heat into light. The light emitted from the base of the mantle is so brilliant that it is painful to look at directly; therefore, such lamps, if intended for office or domestic use, should be provided with a shade e of white or opal glass, to modify the intense glare.

232. The mantle is made by saturating a delicate woven cotton fabric into a dense solution of several earthy oxides, such as magnesia, zirconia, etc. The mantle is then baked, and finally its temperature is raised high enough to destroy the cotton fibers, leaving the coating of oxides standing as a network of fragile crust. The fragility of the mantles is at the present time the chief drawback to this mode of gas lighting.

This lamp is not limited to the use of illuminating gas. Any variety of combustible gas, oil vapor, or gasoline may be used, by providing a suitable burner which is capable of heating the mantle to the proper degree.