Captain Vergnaud's charge is groundless. The superiority of our sporting gunpowders is due to the same cause as the superiority of our cotton fabrics-the care of our manufacturers in selecting the best materials, and their skill in combining them.

7. On Detonating Matches.

This subject has been so ably treated in the report of MM. Aubert, Pellissier, and Gay Lussac, that I shall confine myself to a few observations, the results chiefly of my own experience. Mr. Howard's proportions of the ingredients for preparing his fulminate of mercury are,

con

The mercury is dissolved by heat in the acid, the solution is allowed to cool to a blood-heat, and then, poured into the alcohol. On heating the mixture slightly, an effervescence soon ensues, the commencement of which is the signal for removing the heat from the matrass or retort; for if it be tinued for some time longer, the chemical action will become furious, and the fulminate will be injured by an admixture of subnitrate of mercury. After the crystalline powder precipitates, the whole is to be thrown on a filter, washed, and dried on a steam-bath.

The authors of the above report say the best proportions are those of Howard; but they appear to estimate them incorrectly, for they prescribe 12 of nitric acid and 12 of alcohol (by weight) to 1 of mercury. We may hence infer that considerable latitude may be used in the proportions of the materials. I consider the latter ones wasteful, since 100 of mercury, with 950 of nitric acid, 1.35 and 850 alcohol 0.835, produce about 120 parts of a perfect fulminate. The supernatant liquid retains nearly 5 per cent. of the mercury, for 5 grains of a dark-grey oxide may be obtained from it by ammonia.

I have analyzed the match-powder collected from fifty detonating caps of French manufacture, taken from a stock found to answer very well in practice. The whole weighed exactly

16.3 grains, being about one-third of a grain per cap. Treated with hot water, it yielded 8.5 grains of soluble matter, of which 7.0 grains were nitre, and 1.5 nitrate of mercury derived from the ill-made fulminate. By boiling again in water, this passed into a yellow subnitrate.

7.2 Grains of insoluble matter were brushed off the dried filter and heated with dilute muriatic acid. The solution being thrown on a filter, this retained 1 grain of carbon and sulphur, while 6.2 grains of fulminate of mercury passed through in the state of a bichloride. The proportions of this match-powder must have been, therefore, 8 grains of a kind of gunpowder, and about 8 of indifferent fulminate of mercury; and yet it exploded very well: it obviously contained more nitre than usually enters into gunpowder.

The proportions deduced by the French commissioners from their elaborate and able researches are 10 of fulminate, and 6 of pulverin (gunpowder meal).

100 grains of fulminate triturated with a wooden muller on marble, with 30 grains of water and 60 of gunpowder, are sufficient to mount four hundred detonating caps.

Desirous

In describing the formation of fulminating mercury, I omitted a curious fact that lately occurred to me. of moderating the reaction of the mixture, which had been overheated, I added a little alcohol from time to time, till its quantity was increased by nearly one half. The fulminate being washed, and laid out on the filtering paper in the air, when nearly dry, minute brilliant points were observed to start up on different parts of its surface, which, becoming larger, were found to be globules of mercury. This metallization went silently and slowly on till nearly one-half of the powder disappeared. An ethereous hydro-carbonate was evidently the agent in this unexpected reduction*.

To the relative conservative powers of different gunpowders, my attention was first drawn by my very intelligent friend, Major Moody, Commanding Royal Engineer of the Government Gunpowder Works; and through his co-operation I hope to be able, in another paper, to prosecute this subject, so interesting in a national point of view.

London, September, 1830.

142

ANALYSIS OF NEW BOOKS.

Commentaries on the Mining Ordinances of Spain. By Don Francisco Xavier de Gamboa. Translated from the Spanish, by Richard Heathfield, Esq., Barrister at Law.

THIS

HIS work is a commentary on the mining laws of Spain and her colonies, having reference, more particularly, to the kingdoms and provinces now constituting the republic of Mexico, in which country it is the principal authority in questions concerning mines or mining. The greater part of the work, as might be supposed, is devoted to the discussion of legal topics; but it likewise contains, interspersed, and by way of digression, a variety of historical and scientific information, on most subjects connected with mining. The object of the author in fact, to have been two-fold :appears, First, to give a complete view of the existing law of mining; which he illustrates by tracing it down from the earliest periods, and by reference to the civil law, the general law of Spain and the Indies, and to cases decided within his own experiencet.

Second, to give as much instruction and useful information as he could collect, on the various subjects connected with mining and the reduction of the metallic ores, of a nature to interest the practical miner and metallurgist, and to lead them to the attainment of greater perfection in their several departments.

Amongst the most interesting of the subjects discussed under this head, is that of the reduction of the ores of the precious metals; under which the author takes an opportunity to describe the processes employed for that purpose in Mexico, at the period when he wrote, and which are, with little or no variation, the same now practised in that country. The Mexicans are not so rude and unskilled in the art of reducing their ores,

The Ordinances themselves have been translated into English by Mr. Thomson, and are before the public.

The new code of mining laws, issued by Charles III. in 1783, very closely follows, in all that concerns the working of the mines, the ordinances illustrated by Gamboa, which it leaves in force where not directly at variance with the regulations of the former. Hence the authority of the work of Gamboa at the present day, in Mexico and the other new republics of America. Few alterations have been made in the laws of mining, by the legislatures of those countries, since the establishment of their independence, besides such as were rendered necessary by the altered form of the government.

as they have been erroneously supposed in this country to be. The processes employed by them, although conducted with little scientific knowledge, and, generally speaking, with no other guide than long practice and experience in the pursuit, are found, from the nature of the ores, and the circumstances of climate and other local accidents, to be better adapted for that country than any others, as is sufficiently proved by the complete failure of Sonneschnied and his colleagues, in their attempt, under the auspices of Charles III., to introduce into America the improvements of Europe *.

The smelting process is described by the author as follows:

Of preparing and mixing the Ores, previous to their reduction by Smelting. Of the construction of the various Smelting Furnaces employed. All the ore raised from the mines is carried to the reduction works, where a receipt is signed on the memorandum brought by the carrier from the mine. The workmen at the reduction works, taught by experience, distinguish the ores adapted for smelting, from those proper for amalgamation, according to their nature, and arrange them separately in an office or store-room. The ore is pounded by beating with a pick or hammer, or more readily, and at less expense, in stamping mills; and being reduced to fragments of a greater or less size, according to its tractability or obstinacy under the action of the fire, it is piled in heaps, or spread out at once for the purpose of making the revollura or revolturon, which is the mixing together of several ingredients, namely, the principal ore, the assistant oret, litharge, impregnated cupels or bottoms of furnaces, plomillos, fierros§, and slag.

In making this mixture, the nature of the ore is attended to; some ores requiring a mixture of all these ingredients, and others not. No general rule, however, can be given for these mixtures, but the miner must frame rules for his own government, founded on repeated experiments and long observation, making him familiar with the nature of the ore.

The mixture, being prepared in the manner above described, is placed in the furnace to be smelted. There are many descriptions of furnaces; some being made of stone, some of mud bricks, and

* See Sonneschnied's Tratado de la Amalgamacion de Nueva España; in the preface to which the author acknowledges his inability, after ten years' labour, to introduce with effect, into Mexico, either the process of Baron Born, or any other, preferable to that of the patio, which, he says, in p. 91 of the work, 'has subsisted two centuries and a-half, and will subsist as long as the world endures.'

+ Metal de Ayuda'-Ore of a more fusible character, mixed with the less tractable ores to assist their fusion.

Plomillos'-Scoriæ charged with lead.

Fierros-Slag or scum, being an unreduced mass of oxides and sulphurets, in which those of iron predominate.

some of clay. In some the smelting is performed with wood, in others with charcoal; in some the mouths or apertures are stopped up, and in others left open. In some, the ore and wood are mingled together; in others, the wood or charcoal is not in contact with the ore, but the flame only, whence they are called reverberatory furnaces.'

Of the smelting of Ores.-Having made the proper mixture, and prepared the furnaces and the machines for supplying them with wind, the smelter must heat or anneal the furnace, if, from being new or newly repaired, it requires it; for, if the ore be thrown in whilst the furnace is cold, it is apt, upon getting warm, to fly or crack, with danger to the bystanders: and if it be moist, in the summer, the same thing will happen, and it will explode with very great force. During the first few hours, charcoal is first thrown in, then a basket of slags, then one of charcoal, and so on, until it be time to add the mixed ore. Half a basketful of this is then thrown in, and upon that a basket of charcoal, and so on, until the furnace begins to work, after which, alternate basketsful of mixed ore and charcoal are thrown in. One or two cargas of charcoal are consumed for each charge, according to the nature of the ore; some ores requiring the furnace to be moderately filled; others, that it should be filled to the top. If the ore be not earthy, but clean, the furnace may be charged freely.

The furnace being thus arranged and brought into play, smelts four charges in twenty-four hours, the ingots being tapped off from time to time; for which purpose, an aperture is made below the bridge of the breast-pan, and the melted portion runs off into the float. The first ingot let off, after repairing the furnace, is called calentadura, and is smaller than the others, because the furnace becomes coated with vitrified ore adhering to it, and care is therefore taken not to throw in rich ores for the calentadura. The fused metal being let off, the bridge is stopped up, the breast-pan is cleared out, charcoal dust is thrown into and around it, and the furnace is again set to work. The portions which may have adhered to it are taken off last of all, and are mixed with the ores in future smeltings.

After the smelting is performed, the furnace is uncharged, which is done in the following manner. The charges of ore being all finished, slags and charcoal alone are thrown in, until all the smelted ore has flowed into the breast-pan, when the furnace throws off a very beautiful flame. The wall of mud bricks and everything which may have adhered to it, are then broken down with a crow or iron bar of about twenty-five pounds weight. And here the unfortunate smelters suffer much, during an hour of great labour; for the furnace is hot in the extreme, the crow is heavy, and the incrusted matter adheres very closely. The smoke and vapour from the slag, which are quenched by pouring water upon them, and which are consequently carried down to the feet of the