Surprise has frequently been expressed that in a salt country in which brine has been manufactured for over twenty centuries, the existence of the rock-salt deposits should only have been discovered in the last two hundred and fifty years, but it must be borne in mind that not only was the brine the best custodian of the secret of its own source, but that, when the problem of the supply had been solved, the danger of tapping and controlling it had still to be overcome. When the supply of brine in many of the springs was cut into, it proved so copious that the sinkers had to flee for their lives and to ascend the shaft among the brine. The fact that the depth at which the brine would be encountered was unknown, explained the inability to provide a safeguard against the sudden inrush of brine, but subsequent observation showed that when the workmen met with the “flag,” or bed of hard marlstone that existed above the top of the rock-salt in many districts, the brine might be expected to be found at high pressure. It was then the practice to case the shaft sides down to the flag to prevent the entrance of surface water, and either to blow through the flag with powder or pierce it with boring rods. At a later period, the shaft was sunk to the approximate point of encounter with the brine, and cased with iron cylinders, the bottom cylinder being furnished with an iron bottom pierced with two pipe holes. A column of pipes was erected in the cylinder, and a set of boring rods was let down each pipe, so that when the flag was bored through, the brine rose until it attained its level in the pipes, while by means of a tap attached to each pipe it was possible to stop the entry of the brine and to empty the shaft. In the brine-shafts employed in the case of the old rock-salt mines, in which the brine was met with at a much higher pressure than in the rock-head brine-shafts, the tapping operation was attended with extraordinary difficulties. The brine in the old workings rose to a height corresponding with that attained by the brine found at the rock-head, and as it had to be tapped through a pillar near the bottom of the old workings, the pressure was proportionately higher. When the holeing was first effected into the brine in the old bottom-bed workings, the rush of the incoming brine was so strong that it passed through the two 5 in. bore holes and rose up a 4½ ft. shaft to a height of 67 yds. in eight minutes. The shaft for tapping this supply of brine was sunk in a pillar of rock-salt, and a drift, fitted with two 5 in. bore-holes, was worked through the intervening face and into the brine. When these bore-holes were knocked through, the brine entered with the report of a cannon, and the engineer and his assistant, leaving their tools behind them, leapt into the bucket and were hastily drawn up the shaft, closely pursued by the rising brine.