Table Showing The Comparative Value Of Different Woods As Fuel

ral charcoal or coke. Peat, which is found in great abundance and easily procured in many of the European countries, where other fuels are scarce, is there much more highly appreciated than it is in the United States. Its qualities have there been thoroughly investigated, and various methods have been contrived for improving its adaptation to the uses for which it is fitted. (See Peat.) As a fuel, this material is much used for domestic purposes in the countries where it abounds, and it is applied both in the raw state and charred to manufacturing operations. In the neighborhood of Carolinen-llutte, near Aichthal, in Styria, successful attempts have been made to smelt iron with it in its raw state, mixed with wood; while the charcoal obtained by charring it has long been successfully applied to the same purpose in Bohemia, Bavaria, France, Russia, and other countries. When freshly cut, peat contains from 80 to 90 per cent. of water, which by drying is commonly reduced to about 25 per cent. When well dried, the heating power of good peat is about the same as that of wood, and about half that of bituminous coal.

The following analyses by Sir Robert Kane and Dr.

W. K. Sullivan are of peat dried at'220° F. The proportions are calculated after deducting the ash. The percentage of the mineral ingredients varies in good peat from 1 to 5; some qualities contain much more, even 33 per cent., but such are worthless for fuel.

The Chinese have for ages been in the habit of mixing the dust from their coal mines with clay and bitumen, and also with refuse matter, and such artificial fuel is in China an article of considerable traffic. The methods introduced in western Europe of utilizing the dust of mineral coals and of charcoal are nearly all based upon the principle of making these substances cohere by thoroughly incorporating them with tar or pitch, and then exposing the compound, When moulded into blocks, in some cases to a current of air to dry them, and in others to a high temperature in vessels serving the purpose of retorts. The former mode of drying is employed for mixtures of charcoal dust, tan, and similar substances, with tar or pitch, and the latter when refuse bituminous coal is used with about a quarter of its weight of pitch. Unless this distillation is conducted at a heat of from 400° to 600° F., so as to dispel the volatile ingredients, there is danger of subsequent spontaneous combustion. At Blanzy in France the coal is separated from the slaty and py-ritous particles, and is then crushed and introduced into a circular metallic basin, which revolves horizontally in a reverberatory furnace, the flame of which passes under it.

Hot tar or pitch is gradually let in upon the coal from a reservoir over the fire to the amount of 7 or 8 per cent., and the mixture is stirred by stationary rakes attached to rods let down through the arched cover. When sufficiently mixed, the materials are made to drop through the bottom into a receptacle, whence they are removed while plastic to the moulds and there pressed by the hydraulic machine. The process of Mr. Bessemer appears to be most highly approved. It is applied only to fine bituminous coal without mixture, the object being to render this plastic by heat and mould it by heavy pressure into convenient shapes. In the softening process the coal may be exposed to the heat long enough for a portion of its volatile elements to be expelled, by which the product is rendered more dense and of the nature of coke; or it may be softened so quickly as to be but slightly altered in its chemical composition. It is then formed into blocks by machinery working under great pressure. There are vast quantities of coal dust lying as waste material at the various extensive coal mines in this country, which might be utilized by mixing with proper proportions of the coal tar of gas works and compressed into bricks by machinery similar to that employed by Bessemer. There can be no doubt that fuel could be furnished in this way at an economical price.-The composition of fuels is commonly expressed by stating the proportions of coke or charcoal, volatile matters, moisture, and ash.

The ultimate analysis reduces the whole to its elements, and expresses the proportions of carbon, hydrogen, oxygen, nitrogen, and the ingredients of the ash. In order to ascertain the fitness of fuel for making gas and producing the fatty products, the proportion of volatile ingredients must first be ascertained, and then the nature of these, as the proportion of the inflammable gases to the liquid products. For other purposes the simple form of analysis is commonly sufficient. The ash is obtained by thorough combustion in an open platinum crucible, continued till nothing is left but the gray or brown ash. The difference of weight of the crucible and its contents before and after the operation, deducted from the weight of the fuel employed, gives that of the ash. Another weighed sample subjected in a similar way to a heat of about 300° will give by loss of weight the amount of moisture; the crucible containing it is then closely covered to exclude the air, and is set in a Hessian crucible also closed with a cover, and containing calcined magnesia. This supports the platinum crucible, and keeps it from contact with the outer one. The whole is now exposed to a red heat for an hour.

The volatile matters are thus driven off, and the difference of weight of crucible and contents before and after the operation gives their proportions. The charcoal or coke is the difference between the crucible with the residuum it contains and that of the crucible alone less the weight of the ash. This may be again obtained by consuming the carbonaceous residue exposed to a current of air. The intense degree of heat evolved in the use of the condensed fuels adds largely to the capacity of heat of the aqueous vapor, and hence further lessens the value of hydrogen in fuels intended for the uses to which they are applied. But for other objects, requiring a quick heat and at the same time diffused over considerable space, the more inflammable fuels are found more efficient; and according to the mode in which their heating power is estimated they may even be classed as producing a greater amount of heat than the more carbonaceous varieties.Whenever the heat from the combustion of hydrogen can be concentrated, as in the oxyhydrogen blowpipe, a more intense degree is obtained than by the use of any other fuel. Other considerations, therefore, besides the chemical composition of fuels, affect their value.