Safety lamp, Williamson, Stephenson type, maker J.Cooke and Co., Birmingham, marking: maker's name, 1878

This is of the Stephenson type lamps, and embodies improvements patented in 1878 by Mr. J. Williamson, of Cannock and Rugeley Collieries. Air for combustion is supplied below the glass cylinder through fine holes protected by wire gauze, supplemented by air passing through the gauze above the glass to the annular space between the outer cylinder and the glass chimney. The latter is protected by a perforated copper cap through which the products of combustion are directed before passing through the outer gauze. A screw lock is fitted. Weight, 3-05 lb. In experiments made by the Royal Commission of 1886, the lamp was found to be safe in explosive mixtures of velocities up to 2,000 ft. per min.