at a low red heat it will inflame bi-phos-phu retted hydrogene gas ; but wire of one-fortieth heated even to whiteness will notinflame mixtures of fire-damp.

These circumstances will explain, why amesh of wire so much finer is required toprevent the explosion from hydrogene andoxygene from passing, and why so coarse atexture and wire is sufficient to prevent theexplosion of the fire-damp, fortunately theleast combustible of the known inflammablegases.

The general doctrine of the operation ofwire gauze cannot be better elucidated thanin its effects upon the flame of sulphur.When wire gauze of 600 or 700 aperturesto the square inch is held over the flame,fumes of condensed sulphur immediatelycome through it, and the flame is inter-cepted; the fumes continue for some in-stants, but as the heat increases they di-minish, and at the moment they disappear,which is long before the gauze becomes redhot, the flame passes; the temperature atwhich sulphur burns being that at which itis gaseous.

Another very simple illustration of the