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of a very refractive porphyritic rock, procured in a quarry, in the vicinity of Pachuca. More than 15,000 francs are annually consumed in the glass house furnaces for wood. A retort costs nearly 14 sous at the manufactory, and more than 50,000 are annually broken.
The nitrous acid used for the separation, is manufactured by decomposing raw saltpetre, by means of a vitriolic earth (colpa) which contains a mixture of alumine, sulphate of iron, and oxide of red iron. This colpa comes from the environs of Tula, where a mine is worked at the expence of the Farm of Colours*. The saltpetre is furnished to the House of Separation, by the royal manufactory of powder. Each retort is charged with eight pounds of colpa, and the same number of pounds of nitrate of impure potash; the distillation lasts from thirty-six to forty hours. The furnaces are round, and unprovided with grates. The nitrous acid which is derived from the decomposition of a saltpetre surcharged with muriate, necessarily contains much muriatic acid, which is carried off by adding nitrate of silver. We may judge of the enormous quantity of muriate of silver obtained in this establishment, if we reflect that there is purified, a quantity of nitrous acid, sufficient to separate seven thousand marcs of gold per annum. They decompose the muriate of silver by fire, melting it with small lead drops. It would be more profitable undoubtedly, to make use in the distillation of aqua fortis, of refined, instead of raw saltpetre. They have hitherto followed the slow and laborious method of purifying the acid by nitrate of silver, because the royal establishment of the apartado, is under the necessity of buying the saltpetre from the royal manufactory of powoder and saltpetre, which will not give out refined saltpetre, under 126 francs the quintal.
* Estanco real de tintes y coloret.
The separation of gold and of silver reduced to grains, for the sake of multiplying the points of contact, takes place in glass retorts arranged in long files on hoops, in galeries from five to six metres in length.* These galeries are not heated by the same fire, but two or three matrasses form as it were a separate furnace. The gold which remains at the bottom of the matrass, is cast into ingots of fifty marcs, while the nitrate of silver is decomposed by fire during the distillation in the retorts. This distillation, by which they regain the nitre and acid, is also practised in a galery, and lasts from 84'to 90 hours. They are obliged to break the retorts to obtain the reduced and chrystallized silver. They might no doubt be preserved, by precipitating the silver by copper, but it would require another operation to decompose the nitrate of copper, which would succeed to the nitrate of silver. At Mexico, the expence of sepa. ration, is reckoned at from two to three reals de plata (from 26 to 39 sous tournois) pe! marc of gold.
16 to 19 feet.
It is surprising that none of the pupils of the school of mines are employed either in the mint, or in the casa del apartado ;. and yet these great establishments ought to expect useful reforms, from availing themselves of mechanical and chemical knowledge. The mint is also si. tuated in a quarter of the town, where running water might be easily procured to put in motion hydraulical wheels. All the machines are yet very far from the perfection which they have recently attained in England and in France. The ameliorations will be the more advantageous, as the manufacture embraces a prodigious quantity of gold and silver ; for the piastres coined at Mexico, may be considered as the materials which maintain the activity of the greatest number of the mints of Europe. . Not only working gold and silver, of which we have already spoken, has been improved
V. in Mexico; but very considerable progress has also been made in other branches of industry dependent on luxury and wealth. Chandeliers, and other ornaments of great value, were recently executed in gilt bronze, for the new cathedral of Puebla, of which the bishop possesses more than 550,000 livres of revenue*. Although the most elegant carriages driven through the streets of Mexico and Santa Fe de Bogota, at 2300 and 2700 metrest of elevation above the surface of the ocean, come from London, very handsome ones are also made in New Spain. The cabinet makers execute articles of furniture, remarkable for their form and the colour and polish of the wood, which is procured from the equinoctial region, adjoining the coast, especially from the forests of Orizaba, San Blas, and Colima. It is impossible to read without interest in the gazette of Mexicot, that even in the provincias internas, for example at Durango, two hundred leagues worth of the capital, harpşicords and piano-fortes are manufactured. The Indians display an indefatigable patience in the manufacture of small toys, in wood, bone, and wax. In a country where the ve
getation affords the most precious productions*, and where the workman may choose at will the accidents of colour and form among the roots, the medullary prolongations of the wood, and the kernels of fruits, these toys of the Indians, may one day become an important article of exportation for Europe. We know what large sums of money this species of industry brings in to the inhabitants of Nuremberg, and the mountaineers of Berchtolsgaden, and the Tyrol, who, however, can only use in the manufacture of boxes, spoons, and children's toys, pine, cherry, and walnut-tree wood. The Americans of the United States, send to the island of Cuba, and the other West India Islands, large cargos of furniture, for which they get the wood chiefly from the Spanish colonies. This branch of industry will pass into the hands of the Mexicans, when, excited by a noble emulation, they shall begin to derive advantage from the productions of their own soil.
We have hitherto spoken of the agriculture, the mines, and the manufactures, as the three principal sources of the commerce of New Spain. It remains for us to exhibit a view of the exchanges which are carried on with
* Swietenia Cedrela and Caesalpinia wood; trunks of Desmanthus and Mimosa, of which the heart is a red, approaching to black.