bear being turned down; they should either be run at full power or extinguished completely. The "Elta" burner, made by Geo. Bray and Co., Ltd., which is shown in Fig. 13, is an injector or atmospheric burner which may be turned low without any deposition of carbon occurring on the tips. A burner of simple construction but which cannot be turned low is the "Luta," made by the same firm and shown in Fig. 14. Of the non- atmospheric type the "Sansair," also made by Geo. Bray and Co., Ltd., is extensively used. It is shown in Fig. 15. In order to avoid the warping, through the heat of the flame, of the arms of burners which sometimes occurs when they are made of metal, a number of burners are now made with the arms wholly of steatite. One of the best-known of these, of the injector type, is the "Kona," made by Falk, Stadelmann and Co., of London. It is shown in Fig. 16, fitted with a screw device for adjusting the flow of gas, so that when this adjuster has been set to give a flame of the proper size, no further adjustment by means of the gas-tap is necessary. This saves the trouble of manipulating the tap after the gas is lighted. The same adjusting device may also be had fitted to the Phôs burner (Fig. 9) or to the "Orka" burner (Fig. 17), which is a steatite- tip injector burner with metal arms made by Falk, Stadelmann and Co., Ltd. A burner with steatite arms, made by J. von Schwarz of Nuremberg, and sold in this country by L. Wiener of London, is shown in Fig. 18. [Illustration: FIG. 17.--"ORKA" BURNER.] [Illustration: FIG. 18.--"SUPREMA" NO. 216469 BURNER.] ILLUMINATING DUTY.--The illuminating value of ordinary self-luminous acetylene burners in different sizes has been examined by various photometrists. For burners of the Naphey type Lewes gives the following table: ___________________________________________________________ | | | | | | | | | Gas | | Candles | | Burner. | Pressure, | Consumed, | Light in | per | | | Inches | Cubic Feet | Candles. | Cubic Foot. | | | | per Hour. | | | |_________|___________|____________|__________|_____________| | | | | | | | No. 6 | 2.0 | 0.155 | 0.794 | 5.3 | | " 8 | 2.0 | 0.27 | 3.2 | 11.6 | | " 15 | 2.0 | 0.40 | 8.0 | 20.0 | | " 25 | 2.0 | 0.65 | 17.0 | 26.6 | | " 30 | 2.0 | 0.70 | 23.0 | 32.85 | | " 42 | 2.0 | 1.00 | 34.0 | 34.0 | |_________|___________|____________|__________|_____________| From burners of the Billwiller type Lewes obtained in 1899 the values: