TROUBLES WITH THE LIME LIGHT [Ch. IV 114 ether vapor is inflammable and takes the place of hydrogen or coal gas. The pure oxygen mixed with it just before it emerges from the burner gives the necessary intensity to the flame. In using this outfit it is necessary to follow very precisely the directions of the manufacturers to avoid accidents. In particular, one must be sure to turn on the oxygen-ether first and light it; then turn on the pure oxygen until the light is best. In turning the light out: Turn off the oxygen first, then after a moment, turn off the oxygen-ether supply. The oxygen produced from one charge of 3^ pounds of the sodium peroxide (oxone) gives about 6.6 cubic feet of oxygen gas, enough to last from two to three hours for the magic lantern. One filling of the ether saturator requires about one pound of sul¬ furic ether and will supply the ether vapor for the charge of oxone. It is said by the manufacturers that if used economic¬ ally the single charge of oxone and ether will supply a double lan¬ tern for an entertainment lasting an hour or an hour and a half. Troubles with the Lime Light § 180. Snapping out of the light.—This is usually due to an excess of oxygen. The oxygen should always be less than the hydrogen or any of its substitutes, i. e., illuminating gas, ether or gasoline vapor, acetylene gas. To invert the statement, the hydrogen or its substitutes, i. e., the inflammable gas or vapor should be in excess of the actual combining proportions. If the lime is too close to the burner tip the light will snap out. In case the light snaps out, at once turn off the oxygen. Light the hydrogen and slowly turn on the oxygen again until a satis¬ factory flame is obtained. Be sure the lime is not too close to the burner tip. § 181. Going out of the light.—This may be due (1) to a lack of one or of both the gases used, that is, the supply may be exhausted. Look at the capacity meter. (2) Some of the valves may be clogged. (3) A rubber tube may have split or come off at the connection.