Fixed carbon 55. Volatile matter 37.5 Ash 5.4 Water 1.4 Sulphur .7 ――――― Total 100 An analysis of coal from the Pittsburgh region would show its percentage of carbon to be from 58 to 64, and of volatile matter and ash to be proportionately less. There is no strict line of demarcation between the anthracite and the bituminous coals. They are classed generally, according to the amount of carbon and volatile matter contained in them, as:―― Hard-dry Anthracites, Semi-Anthracite, Semi-Bituminous, Bituminous. Coals of the first class contain from 91 to 98 per cent, of carbon, and of the second class from 85 to 90 per cent. The volatile matter in the third class is usually less than 18 per cent., and in the fourth class more than 18 per cent. of its composition. The anthracite coal is hard and brittle, and has a rich black color and a metallic lustre. It ignites with difficulty, and at first burns with a small blue flame of carbonic oxide. This disappears, however, when ignition is complete. No smoke is given off during combustion. Semi-anthracite coal is neither so hard, so dense, nor so brilliant in lustre as the anthracite, though when once fully ignited it has all the characteristic features of the latter in combustion. It is found principally at the western ends of the anthracite coal basins. Bituminous coal is usually deep black in color, with little or no lustre, having planes of cleavage which run nearly at right angles with each other, so that when the coal is broken it separates into cubical fragments. It ignites easily and burns with a yellowish flame. It gives off smoke and leaves a large percentage of ashes after combustion. That variety of it known as caking or coking coal is the most important. This is quite soft, and will not bear much handling. During combustion it swells, fuses, and finally runs together in large porous masses.