3.--Cannel coal; dull color, breaks like resin, and somewhat resembles jet. Burns brilliantly, and splits with a crackling noise when in the fire. It affords the best gas. 4.--Glance, or Kilkenny coal; steel-grey color and metallic lustre. Burns without flame or smoke, somewhat like charcoal. 5.--Lignite, or brown coal; is an imperfectly formed coal. The quantity of coal used is rapidly increasing owing to the extensive number of steam engines used, especially for navigation and railway transit; and it is a problem, not yet determined, how long the coal existing in Great Britain is likely to last; the lowest statements make it but little below a thousand years. SULPHUR. Sulphur, also called Brimstone, is a natural production, and is found either pure, or combined with metals forming ores, for the most part called “pyrites,” as, iron pyrites, copper pyrites, &c. In chemical language these compounds are called “sulphurets” or “sulphides.” Sulphur is one of the elements; that is to say, it is a simple body, or one neither capable of being made nor separated into other ingredients. It is crystalline, of a bright yellow color, very inflammable and volatile, burns with a blue flame and gives off pungent fumes of sulphurous acid. It is got pure by distillation from various substances containing it, and in Sicily is found nearly pure as a volcanic product. Sulphur is chiefly used for the manufacture of sulphuric acid and gunpowder, and was also largely used for making matches, but phosphorus (a still more inflammable substance) has almost superseded it in the manufacture of this necessary article. PLASTER OF PARIS, OR GYPSUM.