wire gauze cylinders, coal dust thrown infothe lamp burns with strong flashes andscintillations; the miners were at firstalarmed by an effect of this kind producedby the dust naturally raised during theworking of the coals. I have made anumber of experiments on this subject; butthough I have repeatedly thrown coal dust,powdered rosin, and witch meal, throughlamps burning in more explosive mixturesthan ever occur in coal mines, and thoughI have kept these substances floating in theexplosive atmospheres, and heaped themupon the top of the lamp when it was redhot, yet I never could communicate ex-plosion by means of them. Phosphorusor sulphur are the only substances whichcan produce explosion by being applied tothe outside of the lamp; and sulphur, toproduce the effect, must be applied in largequantities, and blown upon by a currentof fresh air.

It will be unnecessary to caution theworkmen against heaping sulphur, or gun-powder, or pyrites, which afford sulphur bydistillation, upon their lamps; and suchdust from these substances as can float in