As soon as the miners had sunk the shaft to the depth of the sole or floor of the mine and had made an opening large enough for their purpose, they proceeded to blast off enough rock to form a chamber about 5 ft. high. This formed, they advanced by blasting off the rock-salt from the face of the seam. The salt was loaded into waggons, which ran along small railways to the mouth of the shaft. The men engaged in blasting the rock and squaring the walls and pillars (for these were left quite square and well hewn) were called _miners_; those who loaded the trucks and conveyed them to the shaft were _ferriers_. They were a fine set of men, and their occupation, compared with coal-mining, was a very healthy one. The mines were of an equable temperature, and were sufficiently warm for the men to dispense with their shirts. Being lofty, the air was pure, except when excessive blasting was undertaken. The greatest number of men employed in one pair of shafts was about eighty, and the quantity of blasting powder used by that number in the course of a day averaged 1 cwt. Safety fuses were seldom used, the charge being fired by a straw filled with fine powder, which was lighted from a candle. Many of the mines were of considerable size, and some of them increased at the rate of about an acre annually. The quantity of rock-salt mined was small compared with coal. No mine in the district yielded above 40,000 tons per annum. Rock-salt is more free from danger than most kinds of mining; no explosions occur, for there are no deleterious gases, and accidents are rare. In a general way the rock-salt strata are remarkably free from carbonic acid gas, and in only one instance in Northwich, and twice at Meadow Bank, Winsford, does fire-damp appear to have been met with, and then only at pipe veins and in very small quantity. There are no falls of earth, as in coal mines, for the rock-salt is extremely tenacious, and the miners never undermine it but blast it, which is a much safer operation. The two great dangers to which rock-salt mining is exposed, though they rarely result in loss to human life, are the falling in of the mine bodily, or of the shafts and neighbouring earths, and the breaking in of brine either at the head of the top-rock shaft or from old mines, long disused, and full of brine.