For dimensions of furnaces, etc., see STEAM-ENGINE: Economy of F. will be best secured, first, by accomplishing perfect combustion both of the fixed and volatile parts of the F.; and secondly, by regulating the amount of air, as any excess of this has to be passed on to the chimney at the same high tempera ture as the true products of combustion.
The abundance or scarcity of food has a great effect on the general interests of a country and the comfort of its inhabitants. The wealth and prosperity of Britain must be attributed in no small degree to the abundance of coal in those districts both of Eng land and Scotland in which ironstone is most abundant, and in which, therefore, the coal is required as F. for smelting it. But even for the most ordinary uses of domestic economy, the scarcity of F. in some parts of the world causes much hardship to their inhabitants, whilst its abundance in others is one of their greatest natural advantages. Coal, wood, and peat are the three kinds of F. principally used; coal being indeed the vegetation of former ages—or rather of former geological periods—the product of their sunshine and their showers, treasured up for the present; peat, a recent formation. Coal may be said in general to be of about twice the the value of wood as F., weight for weight, in its heating power. In those parts of the world in Which coal is not found,
or to which it cannot beeasily—or as yet profitably—conveyed, the preservation of for ests is of great importance, and trees are not unfrequently planted, as in some parts of Europe, in hedgerows and otherwise, chiefly in order to provide a supply of fuel. For the same reason, pollarding is resorted to, the branches being used as F., and the trunk left to produce now branches. Only some kinds of trees are adapted to this mode of treatment. In some regions, as on some of the steppes of Asia and other tree less plains, the dried dung of herbivorous animals is much used as fuel. In cases of less extreme necessity, all kinds of vegetable refuse arc used. Thus, in many parts of the continent of Europe, things are carefully gathered up for F. whi'-h in any part of Britain would most probably be burned on the field, to get them out of the way. But it is not easy to compute the benefit derived by many parts even of Britain, particularly the inland parts, from the recent great increase of the facilities of communication and of the trade in coal. • ALA110, a t. of Spain, in the province of Murcia, 18 m. s. from Murcia, at the northern base of a range of hills, and at a short distance from the canal of Murcia. Pop. 6,250.