of maize, 656 loads of chile (capsicum), 1770 barrels of brandy, 1682 beeves, 14,949 sheep, and 8869 hogs.

The most important mines of this intendancy, considering them only in the relation of their present wealth, are,

La veta Biscaina de Real del Monte, near Pachuca; Zimapan, El Doctor, and Tehulilotepec, near Tasco.

Diputaciones de Mineria, or Districts:

11. Pachuca.

12. El Doctor.

13. Zimapan.

14. Tasco.

15. Zacualpan.

16. Sultepec.

17. Temascaltepec.

Reales, or places surrounded by Mines: Pachuca; Real del Monte; Moran; Atolonilco el Chico; Atolonilco el Grande; Zimapan; Lomo del Toro; Las Cañas; San Joseph del Oro; Verdozas; Capula; Santa Rosa; El Potosi ; Las Plomosas; El Doctor; Las Alpujarras; El Pinal or los Amotes; Huascazoluya; San Miguel del Rio Blanco; Las Aguas; Maconi; San Christobal; Cardonal; Xacala; Jutchitlan el Grande; San Joseph del Obraje Viejo; Cerro Blanco; Cerro del Sotolar; San Francisco Xichu;

PACHUCA, REAL DEL MONTE, MORAN. 271

Jesus Maria de la Targea; Coronilla or la Purissima Concepcion de Tetela del Rio; Tepantitlan ; San Vicente; Tasco; Tehuilotepec; Coscallan; Haucingo, Huautla; Sochipala; Tetlilco; San Esteban; Real del Limon; San Geronimo; Temas Caltepec; Real de Ariba; La Albarrada; Yxtapa; Ocotepec; Chalchitepeque; Zacualpan; Tecicapan; Chontalpa; Santa Cruz de Azulaques; Saltepec; Juluapa; Papaloapa; Los Ocotes; Capulatengo; Alcozauca; Totomixtlahuaca.

;

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 18th century, the vein of La Biscaina, or Real del Monte has alone been wrought with activity. The working of the mines of Moran was resumed only within these few years; and the mineral depository of Pachuca, one of the richest in all America, has been wholly abandoned since the terrible fires which took place in the famous mine del Encino, which alone furnished more than 19,689lbs. troy weight of silver annually. The wooden work which supported the roof of the galleries was consumed by fire, and the greater number of the miners were suffocated before being able to reach the shafts. 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.

The valley of Mexico is separated from the

basin of Totonilco el Grande, by a chain of porphyritic mountains, of which the highest summit is the peak of the Jacal, elevated according to my measurement with the assistance of the barometer, 10,248 feet 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 further 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 mountain, 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 Jura limestone, near the baths of Totonilco, the slaty limestone of Amojaque, and a gypsum of secondary formation mixed with clay. The position of these secondary rocks which

*Puente de la Madre de Dios.

GEOLOGICAL STRUCTURE.

273

I carefully observed, is so much the more remarkable, as it is the same with that which has been discovered on the Old Continent, according to the excellent observations of MM. 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 splintery hornstone. The presence of hornblende is frequently announced, merely by greenish stains intermingled with common and vitreous feldspar. At very great elevations, for example in the beautiful forest of oak and pine of Oyamel, we find porphyries with a base of pearl-stone, containing obsidian in layers and nodules.

What relation exists between these last beds, which several distinguished mineralogists consider as volcanic productions, and the porphyries of Pachuca, Real del Monte, and Moran, in which nature has deposited enormous masses of sulphuret of silver and argentiferous pyrites? This problem, which is one of the most difficult in geology, will only be resolved when a great number of zealous and intelligent travellers shall have gone over the Mexican Cordilleras, and carefully studied the immense variety of porphyries which are destitute

of quartz, and which abound both in hornblende and vitreous feldspar.

The district of mines of Real del Monte does not display-as at Freiberg in Saxony, Derbyshire in England, or as in the mountains of Zimapan and Tasco in New Spain-a great number of rich veins of small size, on a small tract of ground. It rather resembles the mountains of the Hartz, and Schemnitz, in Europe, or those of Guanaxuato and Potosi, in America, of which the riches are contained in a few mineral depositions of very considerable dimensions. The four veins of Biscaina, Rosario, Cabrera, and Encino, run through the districts of Real del Monte, from Moran and Pachuca, at extraordinary distances, without changing their direction, and almost without coming in contact with other veins which traverse or derange them.

་

The veta de la Biscaina, of less considerable dimensions, but perhaps still richer than the vein of Guanaxuato, was successfully wrought from the sixteenth to the beginning of the eighteenth century. In 1726 and 1727, the two mines of Biscaina and Xacal still produced together 333,969 ounces of silver. The great quantity of water which filtrated through the crevices of the porphyritic rock, joined to the imperfection of the means of drawing it off, compelled the miners to abandon the works when they were yet only 65 fathoms in depth. A very enterprising individual, Don Joseph