The descent to the mines is by a shaft--a perpendicular opening of six, eight, or ten feet square; this opening is used for the general purposes of ventilation, drainage, lifting the mineral, as well as the miners. It varies in dimensions according to the extent of the excavations. In some of the English mines the part of the bed of rock-salt excavated amounts to several acres; but in some parts of Europe the workings are even more extensive. The Wilton mine, one of the largest in England, is worked 330 feet below the surface, and from it, and one or two adjacent mines, upward of 60,000 tons of salt are annually obtained, two-thirds of which are immediately exported, and the rest is dissolved in water, and afterward reduced to a crystaline state by evaporating the solution. It is not yet two hundred years since the Cheshire mines were discovered. In the year 1670, before men were guided by science in their investigations, an attempt was made to find coal in the district. The sinking was unsuccessful relative to the one mineral, but the disappointment and loss were amply met by the discovery of the other. From that time till the present, the rock-salt has been dug, and, as we have seen, most extensively used in England, while the surplus supply has become an article of exportation. Previous to this discovery the consumption was chiefly supplied from the brine-pits of Worcestershire. There is a remarkable deposit of salt in the valley of Cardona, in the Pyrenees. Two thick masses of rock-salt, says Ansted, apparently united at their bases, make their appearance on one of the slopes of the hill of Cardona. One of the beds, or rather masses, has been worked, and measures about 130 yards by 250; but its depth has not been determined. It consists of salt in a laminated condition, and with confused crystalization. That part which is exposed is composed of eight beds, nearly horizontal, having a total thickness of fifteen feet; but the beds are separated from one another by red and variegated marls and gypsum. The second mass, not worked, appears to be unstratified, but in other respects resembles the former; and this portion, where it has been exposed to the action of the weather, is steeply scarped, and bristles with needle-like points, so that its appearance has been compared to that of a glacier. There is also an extensive salt-mine at Wieliczka, in Poland, and the manner of working it was accurately described some years since. The manner of descending into the mine was by means of a large cord wound round a wheel and worked by a horse. The visitor, seated on a small piece of wood placed in the loop of the cord, and grasping the cord with both hands, was let down two hundred feet, the depth of the first galleries, through a shaft about eight feet square, sunk through beds of sand, alternating with limestone, gypsum, variegated marls, and calcareous schists. Below the stage, the descent was by wooden staircases, nine or ten feet wide.