province of New Santander. From the bosom of these mountains * of secondary compact limestone, masses of basalt, and porous amygdaloid rise up as in the Vicentin, which resemble volcanic productions, and which contain olivine, zeolite, and obsidian. A great number of veins of small extent, and very variable in their breadth and direction, traverse the limestone, which itself covers a transition clay state; and the latter perhaps is superimposed to the syenitic rock of the Buffa del Fraile. The greatest number of these veins are western (spathgänge); and their inclination is from 25° to 30° towards the north east.† The minerals which form the gangue are generally found in a state of decomposition. They are wrought with the mattock, the pickaxe, and with the bore, (pointrole.) The consumption of powder is much less than at Guanaxuato, and at Zacatecas. These mines possess also the great advantage of being almost entirely dry, so that they have no need of costly machines to draw off the water. In 1773, Sebastian Coronado, and Antonio Llanas, two very poor individuals, discovered veins in a situation now called Cerro de Catorce Viejo, on the western slope of the Pi *Near the mine del Padre Flores, and on the road from San Ramon to Catorce, (Sonneschmidt, p. 279.) + Descripcion del Real de Catorce, por Don Jose Manuel Gonzales Cueto, 1800 (Manuscript). chaco de la Variga de Plata. They began to work these veins, which were poor and inconstant in their produce. In 1778, Don Barnabé Antonio de Zepeda, a miner of the Ojo del Agua de Matchuala, went over during three months, this group of arid and calcareous mountains. After attentively examining the ravins, he was fortunate enough to find the crest or surface of the veta grande, on which he immediately dug the pit of Guadalupe. He drew from it an immense quantity of muriated silver, and colorados mixed with native gold; and he gained in a short time more than half a million of piastres*. From that period, the mines of Catorce were wrought with the greatest activity. That of Padre Flores alone produced in the first year 1,600,000 piastrest; but the vein only displayed great riches from 50 to 150 metres of perpendicular depth. The famous mine of Purissima belonging to Colonel Obregon, has scarcely ever ceased since 1788, to yield annually a net profit of 200,000 piastres§; and its produce in 1796 amounted to 1,200,000 piastres, while the expences of working did not amount to more than 80,000. The vein of Purissima, which is not 109,383 sterling. Trans. + Upwards of 350,000 sterling. Trans the same with that of Padre Flores, sometimes reaches the extraordinary extent of 40 metres*; and it was worked in 1802, to the depth of 480 metrest. Since 1798, the value of the minerals of Catorce has singularly diminished; the native silver is now rarely to be seen; and the metales colorados, which are an intimate mixture of muriated silver, earthy carbonated lead, and red ocre, begin to give place to pyritous and coppery minerals. The actual produce of these mines is nearly 400,000 mares of silver annually.‡ The mines of Pachuca, Real del Monte, and Moran, are highly celebrated for their antiquity, their wealth, and their proximity to the capital. Since the beginning of the eighteenth century, the vein of la Biscaina, or Real del Monte, has alone been wrought with activity. The working of the mines of Moran was only resumed within these few years; and the mineral depository of Pachuca, one of the richest of all America, has been wholly abandoned since the terrible fire which took place in the famous mine del Encino, which alone furnished more than 30,000 marcs of silver annually§. The wooden work which supported the roof * 131 feet. Trans. 262,526 lib. Troy. Trans. of the galeries was consumed by fire, and the greatest number of the miners were suffocated before being able to reach the pit. A similar conflagration in 1787, put a stop to the working of the mines of Bolaños, which were only again begun to be cleared out in 1792. por The valley of Mexico is separated from the basin of Totonilco el Grande, by a chain of phyritic mountains, of which the highest summit* is the peak of the Jacal, elevated according to my measurement with the assistance of the barometer, 5124 metres† above the level of the sea. This porphyry serves for base to the porous amygdaloid, which surrounds the lakes of Tezcuco, Zumpango, and San Christobal. It seems to be of the same formation with that, which in the road from Mexico to Acapulco, immediately covers the granite between Sopilote and Chilpansingo, near the village of Acaguisotla, and l'Alto de los Caxones. To the north east of the district of Real del Monte, the porphyry is at first concealed under the columnar basalt of the farm of Regla, and farther on in the valley of Totonilco, under beds of secondary formation. The Alpine limestone of a greyish blue, in which is the famous cavern of Danto, called also the pierced moun * See my Nivellement Barometrique, p. 40-42 n. 290-312. † 10,248 feet. Trans. tain, or the bridge of the Mother of God*, seems to repose immediately on the porphyry of Moran. It contains near the Puerto de la Mesa, veins of galena, and we find it covered with three other formations of not so old an origin, which naming them in the order of their superposition, are the Jura limestone, near the baths of Totonilco, the slate-free-stone of Amojaque, and a gyps of secondary formation mixed with clay. The position of these secondary rocks which I carefully observed, is so much the more remarkable, as it is the same with that which has been discovered in the Old Continent, according to the excellent observations of M. M. de Buch and Freiesleben. The mountains of the district of mines of Real del Monte, contain beds of porphyry, which with respect to their relative antiquity, differ a good deal from one another. The rock which forms the roof and the wall of the argentiferous veins, is a decomposed porphyry of which the base sometimes appears clayey, and sometimes analogous to the splintery hornstone. The presence of hornblend is frequently announced, merely by greenish stains intermingled with common and vitreous felspar. At very great elevations, for example, in the beautiful forest of oak and pine of Oyamel, we * Puente de la Madre de Dios. |