8675. Forbes, Sir C. S. May 10. Lighting gas.-In acetylene and other gas lamps, gasoliers, brackets, and like fittings provided with pilot jets, the supply of gas to the main burners is controlled by a mercury-seal valve, actuated by varying the pressure of the gas by means of a cock or otherwise. The mercury-seal comprises a containing cup 1 vented at 14, a gas supply pipe 4 and a cap 5 provided with a depending bell 6 and a tube 11. Normally, the mercury closes the lower end of the tube 11, and the acetylene or other gas can only pass from the bell 6 to the pilot jet 10 through the channel 7 and the tube 9. When, however, the pressure of the gas is increased, the level of the mercury in the bell 6 falls into the lower end of the tube 11 is exposed, whereupon the gas traverses the tube 11, the channel 8, and the tubes 13, to the burners 12. A gas governor is preferably introduced into the circuit, where, as at railway stations, the device is employed to control a group of burners.