During the boyas, the miners are paid by a small share in the daily produce of their labours. They sometimes succeed in improving their shares by stealing the ore, but this is very difficult, so narrowly are they searched when they leave the mine. One man told Dr Tschudi how he had managed to appropriate the richest piece of ore he ever saw. He tied it on his back, and pretended to be so desperately ill, that the corporal allowed him to leave the mine. Wrapped in his poncho, he was carried past the inspectors by two confederates, and the treasure was put in safety. Formerly when a mine yielded polvorilla, a black ore in the form of powder, but of great richness, the miners stripped themselves naked, wetted their whole body, and then rolled in this silver dust, which stuck to them. Released from the mine they washed off the crust, and sold it for several dollars. This device, however, was detected, and, for several years past, the departing miners are compelled to strip for inspection. Like the extraction of the ore, the purification of the silver from the dross is conducted in the rudest and most primitive manner. The consequence is an immense consumption of quicksilver. On each mark of silver, worth in Lima eight and a-half dollars, or about thirty shillings, it is estimated that half a pound of quicksilver is expended. The quicksilver comes chiefly from Spain--very little from Idria--in iron jars containing seventy-five pounds weight. The price of one of these jars varies from sixty to one hundred dollars, but is sometimes as high as one hundred and forty dollars. Both the amalgamation and separation of the metals are so badly managed, as to occasion a terrible amount of mercurial disease amongst the Indians employed in the process. From the refining-houses the silver is, or ought to be, sent to Callana, the government melting-house, there to be cast into bars of a hundred pounds weight, each of which is stamped and charged with imposts to the amount of about forty-four dollars. But a vast deal of the metal is smuggled to the coast and shipped for Europe without ever visiting the Callana. Hence it is scarcely possible to estimate the quantity annually produced. The amount registered is from two to three hundred thousand marks--rarely over the latter sum. Residence in the Cerro de Pasco is highly disagreeable. The climate is execrable; cold and stormy, with heavy rains and violent falls of snow. Nothing less than the _auri sacra fames_ could have induced such a congregation of human beings, from all nations and corners of the globe, in so inhospitable a latitude. The new-comer with difficulty accustoms himself to the severity of the weather, and to the perpetual hammering going on under his feet, and at night under his very bed, for the mines are worked without cessation. Luckily earthquakes are rare in that region. A heavy shock would bury the whole town in the bosom of the earth.