gation, and peculiar advantages of the domestic constitution, which we must content ourselves with recommending to the earnest consideration of every parent. We intended to have adverted at some length, to a subject of very great importance, viz: the duty of Christian Ministers, with regard to the education of their children. There is a mistake we think prevailing upon that subject, which is productive of the bitterest consequences. But as we cannot dispose of it in a closing sentence, we shall take a future opportunity of returning to it.

ART. VI.-Chemical Technology; or Chemistry applied to the Arts and Manufactures. By Dr F. KNAPP, Professor at the University of Giessen. Edited with numerous Notes and Additions by Dr EDMUND RONALDS, Lecturer on Chemistry at the Middlesex Hospital, and Dr THOMAS RICHARDSON, Newcastle-on-Tyne. Illustrated with 212 Engravings on Wood. Vol. I. London, Bailliere. 1848.

Most works of this kind only describe manufacturing processes as they are practised, without entering into "the causes of the effects produced;" but in this work the reader will be made acquainted with the "leading scientific phenomena," as well as with the "practical manipulation." Many authors also attempt to classify various processes of manufacture into what they term mechanical and chemical; upon which, the author of this work justly remarks, that "a separation of this kind is truly impossible, as there hardly exists a branch of manufacture which is exclusively chemical, or which is entirely based upon mechanical principles," and considers that "a perfect separation of the mechanical from the chemical would only lead to a confused perception of the whole." His method, which is original, and which enhances the value of the work much, is to arrange the various manufactures into groups: "The members of each group are connected either by a process common to all, or are dependant the one upon the other, in the several processes of manufacture," so as "to bring together the facts and phenomena which depend upon the same principles."

It would be utterly impossible to do justice to this voluminous work in the short space allowed for observation, still it would be wrong to withhold from the public a sketch of the material so simply, beautifully, and classically arranged and illustrated, with a care unequalled; but which will ultimately secure to it the position of the work of highest authority on manufacturing sub

jects, at the same time that it is much valued by the private individual, for having shown him, that a little attention to the proper heating, lighting, and ventilating of his dwelling, are objects which should be valued, not only as economizing his means, but as securing to him that health, without which his existence upon this earth is misery.

In the introduction we have a very short but graphic sketch of the rise and progress of manufactures, and their influence upon the moral and social condition of man. The technology opens with Group 1, "Branches of manufacture depending upon the process of combustion," and this is treated under two heads, first, "Of fuel and the production of heat," and, second, "Of illumination and lighting materials.”

The author, on the subject of fuel, remarks, that "nearly all operations carried on in the arts require the aid of artificial heat, and hence the means of obtaining this, becomes the very first consideration in every manufacture, and consequently of the highest importance to the internal prosperity of the nation." Under the term fuel, he includes wood, turf, brown coal, common coal, also charcoal, both from wood and turf, and coke, and proceeds to discuss them somewhat in the following order:

There is a full description of various woods and their composition; the season for felling timber for firing purposes; tables giving the amount of water in a great variety of woods, of no little use when we are informed, that "water does not support combustion, but, on the contrary, whilst the wood is burning, it takes up a portion of the heat produced, to convert it into vapour. We have tables of the specific gravities of various woods in the state in which they are used, and of the relative proportions of their elements, carbon, hydrogen, and oxygen, which not only explains the peculiar properties of the individual woods, but is essential in estimating their relative value."

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Turf or peat is next discussed-its formation; its constituents; the methods of preparing it for fuel; a table of the amount of ash left after burning, in a great variety of peat. The need for such a table will not be doubted, when we are told, that "the quantity of ash is so great in some peat, as to render it useless." There is no less than 33 per cent. of ash from some peats, while one per cent. is only to be found in others. We have an analysis of the constituents of peat ash, which may guide agriculturists in its use as a manure for crops.

The next subject is coal: We have an account of the decay of carbonaceous matter to form the varieties of coal, and its relative position in the geological formation of the earth. Brown coal, in all its varieties, is treated fully; tables of the constituents

of a great number of kinds, and of the amount of ash left on burning; the unevenness of this description of coal renders these tables highly useful to the consumer. Mineral coal or coal has had a very large share of attention, and the information developed must be a source of great interest to all classes of society. The distinguishing features of coal are followed by a table of the specific gravities, and ash left on burning, of fifty different kinds, and in an adjoining table, are their constituents. Anthracite coal is as fully described, and with corresponding tables.

We now arrive at "the effects of heat upon fuel.”

"Chemical combination,” says the author, "generally can only exist within the limits of certain temperatures, these limits being greater for simple than complex bodies. The varieties of fuel are not volatile; the chemical equilibrium amongst their elements is destroyed, on an increase of temperature long before their volatilization can be effected. The decomposition caused by heat, is nothing more than an overthrow of the existing arrangements of their elements, and an immediate re-arrangement with the formation of new compounds capable of existing at a higher temperature."

The reasons are given why by heat some fuels produce more numerous compounds than others, and why wood is charred, or converted into charcoal to be used as fuel, with a table of results obtained on converting various woods into charcoal, by a slow and a quick process. Charcoal heaps and mounds are next described, and the processes illustrated with wood-cuts. We have also remarks upon the value of the processes. The charring of wood in furnaces, and the produce of tar, together with all the arrangements, are illustrated, and tables are given of the amount of charcoal, &c. obtained from different woods. Charcoal from turf is next described, and tables of results given. The carbonization of pit coal is a matter of consideration in this country, and has not been lightly treated. The general principles of cookery; the selection of coal for the purpose; the various methods of burning it in heaps, in mounds, and in furnaces, are detailed and illustrated, and the produce and nature of coke discussed and tabulated. This is succeeded by "the relative value of fuel," and we have tables to afford us information on this subject which is considered by the author as most important. He remarks, that

"Common every-day experience is sufficient to show, that different kinds of fuel are by no means capable of producing a like amount of heat. It therefore becomes interesting and important to learn the methods which science has adopted for ascertaining the maximum effect of the different kinds of fuel."

The application of heat is the next subject, and, says the author, "will be fully treated in describing the various arts and manufactures; we shall first consider the heating of rooms exclusively." Here the information is extensive. The construction of rooms, the various modes of heating by stoves, grates, water-pipes, &c., with a view "to establish a proper supply of air to replace the vitiated, that has passed through the lungs." The "effect of heat" is a subject of consideration, and we have the results of coal upon steam boilers; also the effective value of wood, peat, and coal, when burned under well arranged coppers.

This ends the first part of the first group in the original work; but besides numerous additions throughout what we have gone over, the editors have appended much new and valuable information. We have the preparing of soot, lamp-black, &c.; the making of lucifer-matches; a new and improved process for preparing coke; manufacture of a new patent fuel; the heating and ventillating of dwellings, with an account and plans of the recent improvements in grates; and the systems of ventilation adopted in some public and other buildings throughout London, detailed and discussed. The consumption of smoke has also been considered as a subject of great importance, especially in large towns; and out of the very numerous plans patented and projected, two of the most trustworthy have been selected, which are beautifully described and illustrated. We only wish that, for the convenience of the reader, these additions had been introduced in the body of the work.

The second part of the first group, "illumination and lighting materials," opens with an account of the general principles upon which we proceed the best to obtain this object; after which come the materials for producing light, coal, resin, tallow, spermaceti, wax, and the oils. "The fats," says the author, "must be valuable as sources of nourishment: those fats only which are unfit for food, can vie with each other as sources of light, or for the production of soap. For the latter purpose, the use of the fats is dependant upon other grounds; but their value as food, and as sources of light, depends upon the same properties: chiefly upon the very large amount of carbon they contain (70 to 80 per cent.) as compared with the two other constituents" (hydrogen and oxygen).

We have a description of the composition, and tables of the relative value of a number of fats; the processes employed for obtaining oils from seeds and fruits; an account of train-oil, and its purification; together with a very useful table of the fluidity of oils, and the time they take to flow through an aperture, water being considered at 100. Then comes the melting and

purifying of tallow, and the separation of the stearine from the oleine. Spermaceti, wax, and resin are next particularised, and the preparation of turpentine fully described. We have the making of tallow, wax, stearine, and spermaceti candles. This is further elucidated in the appendix by the editors, by a description, and cuts, of the machines now employed for preparing the wicks, dipping, and moulding candles. The evolution of light from candles, the unevenness of burning, and other occurrences, are detailed and explained. The subject of oil-lamps is next under consideration, and occupies a conspicuous part in this work, to which the editors have again added, in the appendix, all recent lamps of any advantage. Gas-illumination begins with its history; the nature of gas; the amount obtained by several Companies from different coals; the constituents of coal-gas before purification; with the entire apparatus, and processes for preparing and purifying it; also the processes for obtaining gas from oils, resins, soap-water, animal matter, and an entirely novel method discovered by Selligue in Paris. In the collection and distribution of gas, we have the shapes of the various gasometers; a description of gas-meters and burners; and, in the appendix, we have, from the editors, the most recent improvements in gas burners. This group finishes with a comparison of the various methods of illumination, with numerous tables. We must remark that this subject alone is illustrated with upwards of eighty woodcuts, most beautifully executed, and clearly delineated.

We cannot bestow so much time upon Group 2d, "Processes of manufacture concerned in the production and application of the alkalis," as we have given to the first group, but we would wish to show the reader that the author does not swerve from the principles upon which the work is based. The author considers the manufacture of the carbonates of potash and soda of the utmost importance, but that "certain other branches of manufacture, such as the production of sulphuric acid, which have not the production of potash or soda for their direct object, are, nevertheless, so intimately connected with this part of the subject, that a description of them cannot be well passed over here without detriment to the general view of the whole." And following out this opinion, we have sulphur, one of the constituents of sulphuric acid, first described, next its purification, with plans, and method of working the apparatus for preparing at one and the same time stick and flowers of sulphur. We have also the obtaining of sulphur from iron pyrites, (which is a compound of sulphur and iron, and found in nature in great abundance,) and some new and successful inventions, given by the edi