Fuel is the aliment or food of fire.

The fuel generally used in Britain is pit-coal : it is attended with considerable expence, that is not a little increased by the enormous waste, arising from the injudicious manner in which the fires are usually managed. Hence different compositions have been proposed, among which that contrived by Count RumfoRd more particularly claims our attention. It is known by the name of kindling' balls, which are composed of equal parts of coal, charcoal, and clay ; the two former are reduced to a fine powder, well mixed and kneaded together with the clay moistened with water ; and then formed into balls of the size of hens eggs, which are thoroughly dried. These balls may be made so inflammable as instantly to take fire from the smallest spark, after they have been dipped in a strong solution of nitre, and then dried. With those three in-gredients, Count RumiFord is of opinion, that a certain proportion of straw, cut very small, or of chaff, or even of saw-dust, may be advantageously incorporated. - The excellence of the fuel thus prepared consists in its economy and cleanliness ; circumstances of the utmost importance, and which are calculated greatly to improve the apartments of the opulent: for, he observes, " nothing is more dirty, inelegant, and disgusting, than a common coal fire." - The Count's invention is somewhat similar to the patent Coal-balls prepared by Mr. Frederick, of which we have already given an account on P. 19.

To this may be added, the improved fuel invented by Mr. Peter Davey, to whom a patent was granted early in the year 1801. The substances he employs are, a mixed coke composed of pit-coal and charcoa,l in various proportions, united previously to the ope-ration of coking. The patentee takes small sea-coal, to which he adds charcoal, saw-dust, tan, or any other materials that may be converted into charcoal, in proportionate quantities : these, however, are not specified, and he simply observes, that for furnaces, or other large fires, the quantity of sea-coal is to be increased ; and, when the fuel is intended to be burned in small fires, it is to be diminished. After mixing the different ingredients, they are to be dried in kilns, and heated so as to make them intimately cohere, and expel the moisture and oily parts, without consuming the substance of the coal: in this state the fuel is fit for use.

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We do not pretend to decide, which of the preparations above-mentioned is preferable; as they are all eminently calculated to introduce economy in one of the most useful articles of domestic conve-nience - fire.

Beside these compositions, various machines have been invented for saving fuel, of which the following are worthy of notice : - In May, 1792, Mr. David Freak-son, of Liverpool, obtained a patent for machinery and operations for the purpose of saving fuel, in the process of evaporating water from solutions of salts, or the waste or leys of soap-makers ; and which may be applicable on other occasions, where the evaporation of water from substances holding it in solution is required. For the particulars of this invention we refer the reader to the 9th vol. of the "Repertory of Arts and Manufac-tures" where he will find the whole process amply detailed.

A patent was likewise granted, in June, 1798, to Mr. George BluNdell, of Bethnall - green, Middlesex, for his invention of a machine calculated for the purpose of saving fuel, and preventing dirt or dust from fires, which he calls an " Economical Receiver." - The apparatus consists of certain receivers, or boxes, formed of metal, either simple, or compound, and which are either square, oval, or of any other shape that may be required, in order to be fitted beneath any kind of grates, stoves, or fire-places. Over this receiver is fixed a grating, or net-work of wire, which intercepts the cinders, and suffers the ashes to fall into the lower part of the vessel. There are likewise sliders, and other pieces pf machinery ; an explanation of which is inserted in the 10th Vol. of the work above cited.