of common salt at its maximum point of saturation; these compounds are the chloride of silver and the sulphate of lead. The solution once made, is run into reservoirs of wood as soon as it has become clear; there the decomposition of the metallic salts is effected with Voltaic couples formed of plates of zinc and of tin-plate, or of copper, or of masses of well calcined charcoal, or also with couples composed of plates of lead and the same electro-negative elements. The plates of zinc or of lead are placed in sail-cloth bags filled with a saturated solution of common salt, and immersed in the saline solution of the metals dissolved out of the ores, the electro-negative plates being immersed in the latter solution; communication between both is then effected by means of metallic slips. With zinc electropositive plates an electro-chemical deposit is obtained upon the electro-negative plates,consisting of all the easily reducible metals-silver, copper, and lead-in a very minute state of division; with lead electro-positive plates, the deposit consists of silver more or less pure according to the proportions of lead which happen to be in saturation. Instead of sail-cloth sacks it would be better to employ boxes of wood, some millimetres in thickness, previously exposed to the action of steam in order to remove all soluble extractive matter; or cells of semi-baked clay, filled as far as possible with fragments of amalgamated zinc and mercury. The action is in this case more regular, and the quantity of zinc consumed is in atomic proportion with that of the metals deposited. By varying the composition of the voltaic couples we may successively separate each of the metals in solution in the salt water. The experiments, the results of which are given in the work of M. Becquerel, were made on quantities of ores varying from 100 grammes (1,543-4 grains) to 1,000 kilogrammes (2,204-85 lbs., or something less than one ton); and the quantities of silver collected in the space of 24 hours have varied from a few decigrammes† to 1 or 2 kilogrammes, so that it was possible to appreciate the advantages and the inconveniences of the electro-chemical treatment of the ores of silver, lead, and copper, particularly of the two first, the preparation of which presents more difficulties than the latter. From what has been just stated, it would appear that the electro-chemical treatment of the ores would be terminated in 24 hours; but in operating with the powerful assistance of an independent pair, the temperature of which would be elevated by means of steam, it could be effected in 18 hours. It is, of course, to be understood that this couple is voltaically connected with the other apparatus; in operating thus, only plates of lead are placed in the latter, of which some act as the electro-positive elements of the circuit, and the others the electro-negative; and although lead acts directly upon the chloride of silver in decomposing it, the two currents in opposite directions, which result from this action, do not appear to injure the effect of the independent couple. In this manner the advantages resulting from the immediate precipitation of the silver by the lead may be *One millimeter = = 0·03937 of an inch. + One decigramme = 2.2048 lbs. = 1,543 grains. combined with those resulting from the electro-chemical action of the independent couple, which transforms each apparatus, at the ordinary temperature, into a voltaic couple. After several operations, in which plates of lead are employed, the salt water will be found to contain only chloride and sulphate of lead, which is to be decomposed by means of lime. As it would be impossible to indicate here all the precautions to be taken in submitting the different kinds of silver and lead ores to the new process of treatment, we shall only add, that the ores the most refractory in amalgamation, and the most difficult in the smelting, such as blende ores and gray copper, may be treated with facility by this process. Argentiferous galenas when the lead is converted into sulphate, and the silver into chloride, may be rapidly treated by the process of amalgamation au cazo, without further loss of mercury than that inevitably produced by the washing of the ore to obtain the amalgamation. M. Becquerel points out the means of thus reducing the loss of mercury. Metallurgists, he believes, will appreciate the mode of treating galena, which admits of immediately extracting the silver without cupellation, when the ore has been roasted under certain conditions, and of then obtaining the lead by electro-chemical means, and containing only insignificant traces of silver. The lead deposited on the electro-negative plates is in a fine state of division, or in the condition of a sponge; when washed, and while still moist, pressed, it is melted in clay crucibles, the surface being covered with charcoal dust to prevent oxidation. Several hundred kilogrammes of lead have been thus melted. The precipitated lead is pyrophorous, and hence it should not be allowed to dry in the air, otherwise it would oxidyze with evolution of heat. In this condition it is peculiarly adapted for the manufacture of white lead. M. Becquerel did not consider it sufficient to merely make his experiments on a large scale; it was also necessary that they should be repeated and judged by a skilful practician; this has been done by M. Duport SainteClair, formerly silver refiner in Mexico, who has communicated the result of his experiments and of his observations in his work entitled "Sur la Production des Métaux Précieux au Mexique." At page 405 of that work the author thus speaks of the electro-treatment of silver ores: "If by one of those eventualities not very probable, but possible, the mine of Almaden ceased to furnish cinnabar, either by a falling in, or from the flowing in of too much water, or finally, from the whole of the ore sufficiently rich in mercury having been extracted, the production of quicksilver, thus reduced to that of the mines of Carniola, would be very inadequate to supply our wants; such an increase of price would take place as would be equivalent in some sort to an absolute deficiency of the article. What would then become of the extraction of silver in Mexico? A few years ago the solution of this question would have been very embarrassing, for no other mode of extracting silver from its ores was known, except that by smelting or by amalgamation. The learned researches to which M. Becquerel has devoted himself, with all that perseverance which the first application of science to industry always demands, have contributed to metallurgy a means perfectly new, in the employment of electric forces. Initiated by the inventor himself in all the details of this new process, I have been able to convince myself of the possibility of its industrial application to the ores of Mexico, as well by the experiments made upon 4,000 kilogrammes (nearly 4 tons) of the ores of the principal districts which I had got brought to Paris about three years ago, as by those which I repeated myself at the localities. The possibility of its application on the great scale once established, the question reduces itself to a comparison of numbers between the cost of the old processes and the new one; and the first researches which I made in metallurgy had in principle no other motives. The results of my researches were favourable to the electro-chemical process for a great number of ores, I do not say alone upon the not very probable hypothesis of an absolute deficiency of mercury occurring, but even with the present high price of that metal. On this account we have a right to be astonished that the process has not begun to be employed; the causes which have prevented this taking place, having general characteristics of sufficient importance in reference to the establishment of every new process, I shall enter, upon this occasion, into some details upon the subject. The simplicity of the apparatus required for the Mexican amalgamation process is itself a considerable obstacle to any innovation; then comes the force of habit in an art practised during three centuries, and one, too, well understood in an economical point of view; and finally, the necessity of operating on considerable masses in order to acquire faith in the process, whilst at the very outset an outlay must be made, so much the more costly that every construction for industrial purposes is very dear in Mexico, must succeed in at length damping the zeal of innovators. "Mercury being the principal chemical agent employed in the present mode of working, its price is of great importance in comparing the processes in use with those which it is wished to substitute for them, since, whether but little mercury be employed, or none at all, there is an evident tendency to diminish the demand for that metal, and on this account to lower its price. "The chance of a fall in the price of an article, where that price depends, as is very generally the case, upon its cost of production, would offer but slight probability of any considerable variation; but in the case of mercury it is quite different, for in consequence of the monoply, its actual price may be considered to be four times its cost of production, and in proportion as its employment becomes less, the price may lower almost suddenly, in a manner disastrous for those establishments employing some new process destined to replace the mercury, or diminish its loss in amalgamation." M. Duport again remarks, and this consideration is important, that independently of the circumstances relative to mercury, we must also take into account those having reference to the employment of common salt, the basis of M. Becquerel's process, and the loss of which could not be neglected, except where the price of this substance would be low; but this is not the case in the greater part of the mines of Mexico, where the price often exceeds forty francs the metrical quintal.* If these difficulties be obviated, nothing further can oppose the employment of the electrochemical process. From this it may be concluded, that in all the mining regions where the common salt is cheap, the electro-chemical process is applicable, provided always that, when the silver ores are the complex sulphurets, there be sufficient fuel in the district for roasting them. For example, the ore of Sainte-Marie aux Mines, in the department of the Haut Rhin, situated in the neighbourhood of large salt works, which present difficulties in their treatment by the methods now in use, may be easily worked by the new process. However great may be the immediate value of these researches of M. Becquerel as applied to Mexican mining, they are scarcely less important * 16s. 3d. per cwt. when viewed in reference to the future progress of metallurgy generally; for they open up a new and untrodden field, the cultivation of which appears destined to completely revolutionize that branch of industry. Should these predictions be verified, the manufacture of metals may one day be freed from the slavery of fuel, and nations whose mineral wealth is now of little consequence from the want of that element may arrive at the first rank in the production of metals. ART. IV. On the Application of the Centrifugal Blowing Machine to High Furnaces. By FREDERICK Marquardt. [BESIDES its great immediate importance to British and Irish iron-masters and founders generally, the following paper may possess special interest in Ireland, in connection with the attempts which are now about being made to puddle iron by means of gas produced from turf, as is practised in Germany, and upon which we shall have much to say in a future number. It may also be deserving of attention in connection with the process of Reece, for obtaining the products of distillation from peat, should that process be found as successful as is anticipated. Any experiments or improvements connected with blowing machines are the more important from the little which has been recently done to improve the present generally clumsy and imperfect machines.] An attempt has been made to apply the centrifugal blowing machine for smelting purposes in the high-furnaces of the Nexahütte in Szaska, in the Banat, near the Turkish frontier of Austria. The object of this paper is to record the results of the trials made, and to describe the construction of the apparatus. The high-furnace here referred to has a diameter of 7 feet at the boshes, and is 33 feet high from the hearthstone to the tunnel-head. The hearth is 18 inches at the bottom, and 29 inches at top; the crucible is 181 inches to the tuyere's, and the whole height of the hearth 5 feet 8 inches.* The ores employed for smelting consist of compact magnetic ironstone, yielding 70 per cent. of raw iron; red and brown hematite, averaging 55 per cent., and earthy iron ochre, and yellow hematite, averaging 30 per cent., and finally, ankerite, yielding 22 per cent. Some of these ores are extremely fusible, but difficult of reduction, and among them, the magnetic ores especially, are so dense and compact that they cannot be completely reduced without repeated roastings. The fuel generally used consists of hard beech charcoal, of which the All the measurements given in this paper, when not otherwise expressed, are English. Austrian cubic foot [1.112 English cubic foot] weighs 12 Austrian pounds [14.8 English pounds]; to this was added, with very satisfactory results, about one-third of ordinary pit coal, of which 13 pounds is equivalent to one cubic foot of charcoal. The two centrifugal blowing fans (one for present use, the other being kept in reserve) have each a diameter of 203 inches, the vanes are 6 inches long; those of one fan being 3 inches wide, and those of the other 4 inches. The wind openings are 9 inches in diameter, and placed somewhat eccentrically in the fan case. The axle is of cast steel, with a maximum diameter in the middle of 3 inches, the journals being only 13 lines. These are tempered to the hardness of glass, and finely polished. The gudgeons consist each of a single piece, carefully and exactly drilled, and composed of an alloy of 84 parts of copper to 16 of tin. An exact and careful setting of the axle in its bearings is absolutely essential, and upon it chiefly depends the durability and effective working of the entire apparatus. In figures 1 and 2, a is the lower side of the pillow-block, b the cover or bonnet with the oil-box, b' opening into it, and c the metal axle cushion. The journals lie on the latter only at both ends, so that a |