ployed. At Chapoltepec, near Mexico, and in the mine of Rayas near Guanaxuato, some experiments have been made of the method of blowing, proposed by M. Baden; a method by which a certain volume of air must be left between the powder and the wadd. Although these experiments have proved the great advantage of the new method, the old has still continued to prevail, on account of the small degree of interest taken by the master miners in reforming the abuses, and perfecting the art of mining.

The lining with wood is very carelessly performed, though it ought the more to engage the consideration of the proprietors, as wood is becoming year after year more scarce on the table land of Mexico. The mason work employed in the pits and galleries*, and especially the walling with lime, deserves a great deal of praise. The arches are formed with great care, and in this respect the mines of Guanaxuato may stand a comparison with whatever is most perfect at Freiberg and Schemnitz. The pits and still more the galleries of New Spain, have generally the defect of being dug in too great dimensions, (artstosshöhe) and of occasioning, by that means, very exorbitant ex

Especially in the mines of Valenciana, Guanaxuato, and the Real del Monte.

pences. We find galleries at Valenciana*, executed with the view of investigating a sterile vein, of a height of eight or nine metrest. They have taken it into their heads, that this great height facilitates the renovation of the air; but the ventilation solely depends on the equilibrium and difference of temperature between two neighbouring columns of air. They believe also, equally without any foundation, that, in order to discover the nature of a very powerful vein, very large galleries of investiga tion are requisite, as if in mineral depositories of from twelve to fifteen metres in extent, it were not better to cut from time to time small cross galleries towards the wall and the roof, for the purpose of discovering whether the mass of the vein begins to grow richer. The absurd custom of cutting every gallery in such enormous dimensions, prevents the proprietors from mul-. tiplying the labours of investigation, so indispensible for the preservation of a mine, and the length of duration of the works. At Guanaxuato, the breadth of the oblique pits dug stairwise, is from ten to 12 metres §; and the perpendicular pits are generally six, eight, or ten metres broad. The enormous quantity of

minerals extracted from the mines, and the necessity for the cables attached to six or eight horse baritels to enter them, necessarily occasion the pits of Mexico to be made of greater dimensions than those in Germany; but the attempt which has been made at Bolaños to separate by a beam, the cables of the baritels has sufficiently proved that the breadth of the pits may be diminished without any danger of the ropes entangling in their oscillating motion. It would in general be very useful to make use of casks, or rectangular parallelopipeds, instead of leathern bags suspended to the cables for the extraction of the minerals. Several pairs of these casks rubbing with their wheels against the conducting beams, might ascend and descend in the same pit.

The greatest fault observable in the mines of New Spain, and which renders the working of them extremely expensive, is the want of communication between the different works. They resemble ill constructed buildings, when to pass from one adjoining room to another, we must go round the whole house. This mine of Valenciana is very justly admired on account of its wealth, the magnificence of its walling, and the facility with which it is entered by spacious and commodious stairs; but yet it exhibits only a union of small works too irregular to merit the appellation of gradual works (ouvrages a gradins) they are true

sacks, with only one opening at the top, and without any lateral communication. I mention this mine, not because it is more faulty than the others in the distribution of its labours, but because it ought naturally to be believed better organized. As subterraneous geometry has been entirely neglected in Mexico, till the establishment of the school of mines, there is no plan in existence of the works already executed. Two works in that labyrinth of cross galleries, and interior pits may happen to be very near one another, without its being possible to perceive it. Hence the impossibility of introducing in the actual state of the most part of the mines of Mexico, the wheeling by means of barrows or dogs, and an economical disposition of the places of assemblage. A miner brought up in the mines of Freiberg, and accustomed to see so many ingenious means of conveyance practised, can hardly conceive that, in the Spanish colonies, where the poverty of the minerals is united to a great abundance of them, all the metal which is taken from the vein, should be carried on the backs of men. The Indian tenateros who may be considered as the beasts of burden of the mines of Mexico, remain loaded with a weight of from 225 to 350 pounds* for a space of six hours. In the galleries of Valenciana

* From 242 to 377lb. avoird. Trans.

and Rayas, they are exposed as we have already observed in speaking of the health of the miners * to a temperature of from 22° to 25° + ; and during this time they ascend and descend several thousands of steps in pits of an inclination of 45°. These tenateros carry the minerals in bags (costales) made of the thread of the pité. To prevent their shoulders from being hurt, (for the miners are generally naked to the middle) they place a woollen covering (frisada) under this bag. We meet in the mines with files of fifty or sixty of these porters, among whom there are men above sixty, and boys of ten or twelve years of age. In ascending the stairs they throw the body forwards, and rest on a staff which is generally not more than three decimetres in length‡. They walk in a zigzag direction, because they have found from long experience (as they affirm) that their respiration is less impeded, when they traverse obliquely the current of air which enters the pits from without.

We cannot sufficiently admire the muscular strength of the Indian and Mestizoe tenateros

* Vol. I. p. 125. At Paris the porters called Forts de la Halle, are generally loaded with bags of flour, which weigh 325 pounds (350 lb. avoird. Trans.) To be received in their corporation, a man must carry for 25 minutes, a weight of 850 pounds, (916lb. avoird. Trans.)