of the silver is generally found to have taken place. The water is then drawn off, and the residue (called polvillos) submitted to the ordinary process in the Patio, not more than one-half of the silver being extracted in the Cazo. The same process is sometimes carried on upon a larger scale, the Cazo being made to resemble an arrastre in shape, with a fire beneath, while the contents are kept in constant motion by two large blocks of wood, attached (like the blocks of granite in the arrastre) to a revolving cross beam, worked by a mule. This system is termed "Beneficio del fondon," a caballo, and is infinitely more productive than that of the simple Cazo; as, from the weight of the blocks, there is no deposit, and the action of the mercury upon the ores is much promoted. If the boiling be continued sixteen hours in lieu of eight, there seldom remains anything for the patio; but as the process is attended with more expence, it is seldom resorted to.
We remained at Catorce five whole days, being constantly induced to defer our departure by the number of objects that unexpectedly claimed our attention. During this interval I visited all the mines described in the preceding pages, nor can I sufficiently express my obligations to their proprietors for the readiness with which they answered my innumerable inquiries, and supplied me with every information that it was in their power to convey. They all seemed most anxious that the resources of their district should be made known to Europe, for
