influence of external changes of temperature, and the increase of the temperature of the water being known by the simultaneous indication of several delicate thermometers suspended in it. The real value of such determinations is simply relative. The imperfect character of most boiler and furnace arrangements, and the large quantity of fuel which passes into the ‘ash-pit’ unconsumed, together with the irregular ‘draught,’ and the amount of heat absorbed by excess of cold air, result practically in an enormous loss of heating power, even under the most careful management. The mechanical condition of a fuel must be considered in estimating its value. In a series of trials instituted by the Government it was a sine quâ non that the toughness of each kind of coal must be such, for naval use, as to resist, without crumbling, the constant friction in the ship’s hold, at the same time that its ‘fracture’ must be such that it packs into the smallest possible space.[319]
[319] For full information on coal and other fuels, refer to Ure’s ‘Dict. of Arts, Manufactures, &c.,’ Percy’s ‘Metallurgy,’ and Watt’s ‘Dict. of Chemistry.’
In the chemical laboratory COAL GAS is now generally employed as fuel. It is cheap and manageable, and, with proper apparatus, may be made to supply almost any amount of heat. Where gas cannot be conveniently procured, OIL and SPIRIT are used as fuel for lamps. See Anthracite, Charcoal, Coke, Furnace, Pitcoal, &c., also below.
Fuel, Econom′ical. Various mixtures have been recommended under this name. The following is one of the best:—
Prep. Small coal, charcoal, or sawdust, 1 part; clay, loam, or marl, 1 part; sand, or ashes, 2 parts; water, q. s.; make the mass up wet into balls. For use, these balls are piled on an ordinary fire to a little above the top bar. They are said to produce a heat considerably more intense than that of common fuel, and ensure a saving of one half the quantity of coals, whilst a fire thus made up will require no stirring, nor fresh fuel for ten hours. The quantity of the combustible ingredient in them should be doubled, when they are intended to be used with a very little foundation of coal.
Obs. Of late years simple FIRE-CLAY BALLS have been much used for radiating heat from parlour-grates, and so effecting saving in the consumption of fuel. They are very useful for partially filling up those roomy, old-fashioned, badly-constructed grates, which are still to be found in many private houses.
Peat and TURF, both recent and charred, are commonly used as fuel by the lower classes, in neighbourhoods where they are plentiful. Fir cones or TOPS contain a great quantity of solid woody in addition to the resinous matter, and are well adapted for domestic fires.
Fuel, Prepared. Syn. Compressed fuel, Patent f., Steam f. Many artificial fuels are now in use. The greater number have one character in common—they are composed of small coal cemented by some bituminous matter. The following are the principal kinds:—
Fuel, Aberdare Patent Steam. From the ‘small’ of the South Wales Steam Coal mixed with coal, pitch, and compressed by hydraulic machinery. The pitch is broken up, and thoroughly mixed with the small coal over a furnace, in iron pans, in which shafts with obliquely attached blades are continually revolving. The mixture is afterwards pressed into iron moulds by a force equal to about 21⁄2 tons per inch. The weight of a cubic foot of this excellent fuel is 80 lbs.; the space occupied by 1 ton, 28 cubic feet.
Fuel, Case and Morris’s Patent. From the ‘small’ of the ‘best steam coal,’ ground moderately fine, treated so as to absorb a certain portion of liquid coal tar, and then pressed by machinery into blocks. It is said to occupy less space by about 10% than ordinary coal.