When a mine is very productive, it is said to be in ‘boya;’ and when such periods of affluence take place in several of the mines at once, the population of Pasco sometimes increases to double or treble the usual number. The Peruvian miners are no less dishonest than their fellow-workmen in Mexico, and equally cunning in robbing their employers. On the other hand their patience and perseverance are unrivalled. Satisfied with the coarsest food, and with a still more miserable hut, they undergo an amount of bodily toil which no European could endure. Their only solace is the chewing of Coca, the mysterious plant to which they ascribe such wonderfully stimulating powers, and which has at length begun to awaken the curiosity of European chemists and naturalists.[46] When a ‘boya’ raises their earnings to a considerable sum, they spend it in drunkenness, and never think of returning to their work until their last farthing or their last credit is exhausted. The mineros, or proprietors of the mines, are almost equally uncivilised. Passionately devoted to gambling and mining speculations, they are commonly deeply in debt to the capitalists of Lima, who advance them money at the rate of 100 and 120 per cent.; and when a ‘boya’ favours them, this sudden increase of wealth is merely the prelude of new embarrassment. Footnote 46: The seventeenth chapter of ‘The Tropical World’ is devoted to the Erythroxylon Coca. According to law, all the produce of the silver mines should be sent to the Callana or Government smelting-house; but in order to avoid the heavy duties levied by the State, vast quantities are smuggled to the coast. The annual produce registered at the Callana amounts to about 300,000 marks, but perhaps as much again is exported in a clandestine manner. Besides the mines of Pasco, Peru possesses many others of considerable value, situated chiefly in the provinces of Pataz, Huamanchuco, Caxamarca, and Gualgayoc. The famous Cerro de San Fernando de Gualgayoc, fourteen leagues from the town of Caxamarca, is an isolated mountain traversed by numberless veins of silver. Its summit is sharply serrated by a multitude of tower-like or pyramidal pinnacles, and its steep sides are not only pierced by several hundred galleries for the extraction of the ores, but also by many natural openings or caverns, through which the dark blue sky is visible to the spectator standing at the foot of the mountain. The singularity of aspect is increased by the numberless huts, sticking like nests to the slopes of the fortress-like mountain wherever a ledge allowed them to be constructed. During the first thirty years after the discovery of the mines from 1771 to 1802, they yielded considerably more than thirty-two millions of dollars, and are still very productive.