As the high table-land is altogether unproductive, provisions and other necessaries are brought from the valleys on the backs of mules. That is the only practicable mode of carriage; although it is a curious fact that, during the War of Independence, cavalry and artillery were transported to these heights, and two battles were fought close to Pasco. At the latter of these Bolivar had ten thousand troops besides artillery in the field, and Canterac, the royalist general, opposed him with an equal number. They must certainly have had a taste for fighting under difficulties if they dragged themselves, their guns, and horses up these mountains for no other purpose. An English firm at Callao, which has considerable mining property on the Ceno de Pasco, has recently procured from England a quantity of improved machinery for the extraction of the silver from its ore. The old method is still commonly practised, that is to say, the ore is amalgamated with quicksilver by treading together quicksilver and ore beneath the feet of mules and horses; this proceeding causes a considerable loss of quicksilver--ruins the feet of the animals, and does not properly fulfill its purpose. The quicksilver--nearly all of which it brought from Europe--is afterward evaporated by the application of heat. Coal is found on the Puna. The whole annual produce of the mines of Ceno Pasco once reached the amount of eight millions of dollars, or one million, six hundred and fifty thousand pounds; but the returns now do not probably reach half that sum. There is in the city a government establishment, at which all the silver is marked before being sent to Lima. It is usually melted into large oblong flat bars, some of which weigh from sixty to eighty pounds. These are conveyed to the capital on mules, commonly with no protection except that of the mule-drivers, although the Sierra may be swarming with the bandit montoneros. These gentlemen do not consider it convenient to intercept the silver on its downward passage, they preferring to wait for the coin that is returned in payment. With this upward freight a strong escort is always sent, and when it is attacked, a fierce battle ensues, that often ends in favor of the robbers.