142

I have often made lamps in which sur-faces of glass were used for transmittinglight without a guard of wire-gauze, theygive more light, but they are highly dan-gerous, and ought never to be used. Thickplates of mica,* (Muscovy glass,) may, how-ever, be safely employed, though greatcare must be taken in this case that theradiating and cooling surfaces, where thefire-damp burns, are extensive, and all theprecautions mentioned, page 19, must beadopted ^

Where a lamp is permanently to be fixedin a part of a mine ; it will afford a betterlight if some of the surfaces are of mica ;but for lamps which are constantly to be

* From a very able report on the safety-lamp, drawnup by order of the Chamber of Commerce of Mons,and furnished with some very intelligent and scientificnotes by M. Gossart, President of the Chamber, itappears that lamps with plates of mica have been usedin Flanders. M. Gossart quotes an instance whichproves the danger of glass. “ A director of the workshaving descended in the colliery of Tapatouts, with a 'lamp of which the base of the cylinder was of glass, adrop of water fell upon and broke the glass, and de-tached a piece which would have opened a communi-cation for explosion ; but the air fortunately at the mo-ment was not adulterated with fire-damp.”