[The northwest country, or Upper Mississippi Valley, is among the most remarkable in the world for the variety and abundance of its mineral deposits, and especially for those which are of most extensive use in the arts. The sulphuret of lead occupies about one degree of latitude, extending north from a point on the Mississippi, about eight miles below Galena, and lying on both sides, varying in width, till it covers as great an extent from east to west. On the east side of the river the lead-ore is found principally in a clay matrix, at a depth of sometimes only five or six feet from the surface; on the west side of the river it runs at the depth of one hundred feet or more, overlaid with magnesian limestone. To the south-west of the lead deposit is a very abundant bed of iron, about forty miles long by twenty-five broad. The copper region extends north from the lead deposits to Lake Superior; it embraces about three hundred square miles. To the south of the lead region is a vast bed of bituminous coal of good quality, at no great distance below the surface. In the mineral district there are about four thousand persons employed in digging lead-ore. The value of the lead annually produced is estimated at $1,500,000. A considerable quantity, in form of pig-lead, is exported to China.] Quicksilver—a metal so important in separating silver from its ores, and in other arts as well as in medicine—occurs either liquid in the native state, or combined with sulphur in that of cinnabar. It is found in the mines of Idria and some other places in the Austrian empire, in the Palatinate on the left bank of the Rhine, and in Spain. The richest quicksilver mines of Europe, at the present day, are those of Almaden, where the quicksilver is found in the state of sulphuret chiefly. These mines were worked 700 years before the Christian era, and as many as 1200 tons of the metal are extracted annually. It occurs in China, Japan, and Ceylon, at San Onofro in Mexico; and in Peru, at Guancavelica, the mines of which, now almost deserted, produced, up to the beginning of the present century, the enormous quantity of 54,000 tons of quicksilver. The discovery of quicksilver mines in California has been announced.