FUEL is any combustible matter employed for the purpose of creating and maintaining heat. In the early ages of the world, wood must have constituted, as indeed in many countries it does to this day, the principal fuel employed. Charcoal, another kind of fuel, is merely wood that has undergone imperfect combustion, so as to expel its hydrogen and oxygen, and to leave the greater part of the carbon. Peal, or turf, which is a congeries of vegetable matter, in which the remains of or ganisation are more or less visible, is used in many countries as fuel. In this country coal furnishes the great supply of fuel. Coke bears nearly the same relation to coal that charcoal does to wood. In the East, dried camel's dung is often used for fuel.
The number of substitutes for coal introdu ced within the last few years has been surpri singly large. Oram's patent fuel was planned with a view to make use of the small coal which is so extensively left to wsste at the mouths of the pits ; this coal to be mixed with earthy substances, such as sand, marl, clay, or alluvial deposit ; or with some bitu minous substance, such as mineral tar, coal tar, gas tar, pitch, resin, or asphaltum ; or with saw dust, coke dust, or breeze. In short
this was one of those vague patents which defeat their own purpose by the wideness of their grasp.
Mr. C. W. Williams, managing director of the Dublin Steam Packet Company, has pa tented three or four inventions for artificial fuel in which peat shall be one of the ingre dients. The peat, after being dried, is pres sed with great force, to expel the moisture with which it is saturated ; and it is then mixed with some bituminous substance. By different modes of treatment Mr. Williams produced a very dense brown combustible so lid, a charcoal twice as compact as hard wood charcoal,an artificial coal, and an artificial coke.
All the more recent patent fuels consist of various combinations of the substances noticed above. Bessemer's, Buckwell's, Cowper's, Snowden's, Reece's, Green's—all hare a cer tain. family resemblance, however they may differ in details. Warlich's patent fuel has been found to possess certain favourable qua lities for use in steam-boats. See also CAR BON ; CHARCOAL ; COAL ; CORE ; PEAT.