A great step forward in countering the problem of firedamp came when safety lamps, intended to provide illumination whilst being incapable of igniting firedamp, were brought forward by both George Stephenson and Humphry Davy, in response to accidents such as the Felling mine disaster near Newcastle upon Tyne which killed 92 people on 25 May 1812. Davy experimented with brass gauze, determining the maximum size of the gaps and the optimum wire thickness to prevent a flame passing through the gauze. If a naked flame was thus enclosed totally by such a gauze, then methane could pass into the lamp and burn safely above the flame. Stephenson's lamp (the "Geordie lamp") worked on a different principle: the flame was enclosed by glass; air access to the flame was through tubes sufficiently narrow that the flame could not burn-back in incoming firedamp, and the exiting gases were too weak in oxygen to allow the enclosed flame to reach the surrounding atmosphere. Both principles were combined in later versions of safety lamps.