SOLID FUELS.
Varieties of Coal.—The five most important varieties of coal are anthracite, dry bituminous, caking bituminous, cannel and lignite.
Anthracite coal is found principally in the Allegheny Mountains and in the • Rocky Moun tain region in Colorado. It is a hard, lustrous variety and breaks up easily at a high tempera ture. It consists of 93 to 95 per cent carbon and 2 to 4 per cent hydrogen and burns with very little flame and smoke, unless containing an excess of moisture and gives an intense heat. There is a variety known as semi-anthra cite which contains 90 to 93 per cent carbon and 4 to 5 per cent hydrogen, but it is not as hard as true anthracite and burns with a short flame. Owing to its great brittleness, a large part of anthracite gets broken into small pieces; therefore, in order to obtain the best results it should be fired on grates having small air spaces. The various commercial names and sizes of anthacite coal used in industrial fur naces are as follows: °Chestnut° coal passes over a round hole seven-eighths of an inch in diameter and falls through a hole one and one-half inches in diameter. °Pea° coal passes over a hole nine sixteenths of an inch in diameter and falls through a hole seven-eighths of an inch in diameter. °Number One Buckwheat' passes over a hole three-eighths of an inch in diameter and falls through a hole nine-sixteenths of an inch in diameter. °Number Two Buckwheat° or °Rice° passes over a hole three-sixteenths of an inch in diameter and falls through a hole three-eighths of an inch in diameter. "Number Three Bucicwheat° or °Barley° passes over a hole three-thirty-seconds of an inch in diameter and falls through a hole three-sixteenths of an inch in diameter. °Dust° includes all that falls through a hole three-thirty-seconds of an inch in diameter. The size of coal used has a con siderable influence on the amount of heat pro duced, owing to its effect on the draft. With a poor draft, fine coal is consumed too slowly to be effective. Coal is most efficiently used in separate sizes, which afford regularity of draft, whereas mixed sizes have the effect of choking the fire.
Bituminous coal contains less carbon and more hydrogen than is found in anthracite.
The dry variety is found in Maryland and Vir ginia and the caking variety chiefly in the Mis sissippi Valley. Dry bituminous coal contains 84 to 89 per cent carbon and 5 to 6 per cent hydrogen and burns freely, without caking and with very little smoke. The caking coals be come pasty or swell and cake when burning. Caking bituminous coals contain from 80 to 85 per cent carbon and 5 to 6 per cent hydrogen and are largely used for making illuminating gas.
Cannel coal, also known as long-flaming bituminous, contains from 65 to 85 per cent carbon and 5 to 8 per cent hydrogen. It is found in Pennsylvania, Indiana and Missouri. All varieties of cannel coal have a strong tendency to smoke and some of them cake when heated.
Lignite, also known as brown coal, contains from 55 to 75 per cent carbon and 5 to 6 per cent hydrogen. It is found in the Dakotas, Colorado, Texas, Washington and Alaska. It is a substance intermediate between peat and coal and contains some moisture and mineral matter. The poorer varieties have a low fuel value.
Peat consists of decayed roots and foliage consolidated into •earthy matter. It is cut out of bogs and swamps and then dried, usually by being stacked in the air. If it is sufficiently compact it is burned without being previously compressed; otherwise, it is pulverized and com pressed into briquettes, and sold as an arti ficial fuel. The amount of ash varies from 5 to 12 per cent. Recent experiments in the carbonizing of peat have greatly increased its value as an effective fuel. It is transformed into peat charcoal by the process used in making wood charcoal and into peat coke or semi-coke in special apparatus. In powdered form peat has been used successively as a locomotive fuel on the Swedish national railways, the powder being blown into the fire with an air-blast. A small percentage of powdered bituminous coal is added to the peat powder. In the semi coke process the peat is pulverized in water, carbonized and then pressed into briquettes: Peat charcoal has a calorific value of about 12,500 B. T. U. per pound and peat coke a calor ific value of 14,500 B.T.U. per pound.