The amalgamating process being at length ended, the mass is washed in large vats, through which streams of water are made to pass, so as to drive away the lighter particles of the mud and to leave the heavy amalgam at the bottom of the tub. After being strained through the strong canvas bottom of a leathern bag, in order to separate the superfluous mercury, the amalgam is finally heated in large retorts, when the quicksilver is volatilised and the pure silver remains behind. As a considerable quantity of mercury is thus lost, this metal has always had a great influence on the working of the Mexican mines. When, in times of war, the importation of quicksilver from Europe was stopped, thus causing a considerable increase in its price, the ores accumulated in the magazines, as their poverty made it impossible to meet the additional expense; and then it not unfrequently happened that proprietors, possessing ores to the amount of several millions of dollars, were unable to pay their current expenses. In the last century, the Mexican mines annually required sixteen thousand hundredweight of mercury, which was furnished chiefly by the mines of Almaden, Huancavelica, and Idria. The sale of mercury to the various mining proprietors was a Government monopoly. The quantity of silver produced by the Mexican mines in 110 years, ending with the first year of the present century, amounted to about ninety-eight millions of pounds troy, and the total value of the gold and silver produced from 1689 to 1803 to about 285 millions of pounds sterling. The production was most abundant in the years 1805, 1806, and 1809, when it reached the sum of twenty-six and twenty-seven millions of dollars. It then fell enormously during the revolutionary wars; but the English mining mania of 1824 having furnished the necessary capital for the re- opening of a large number of mines, it again gradually rose, and even reached during some years the rate of its most flourishing period. But it never amounted to one-third of the value which is now annually extracted from our coal mines; and while the latter open new and unbounded sources of wealth by the activity they communicate to numberless branches of industry, Mexico—a prey to bigotry, ignorance, anarchy, and sloth—remains, in spite of her silver mines, as poor and as barbarous as ever.