occurrence, but happens either when there is an irruption 

 of water into a salt mine, which flow of water is stopped 

 before the mine is drowned out ; or, when water in greater 

 or lesser quantities finds its way down the shaft. The 

 water in these cases settles itself in the lowest portions of 

 the sole or floor of the mine, and remains there for many- 

 years. (The Sinkwerks of Ischl and neighbourhood are also 

 examples during the time the water is at rest, but as this 

 water is frequently conveyed to the chambers in the salt 

 artificially, and removed in the same manner, they belong 

 more properly to another section of my subject.) As soon 

 as the fresh water reaches the salt a process of solution 

 commences, and proceeds until the water is fully saturated — 

 that is, until it has taken up about 26 per cent of salt.* 

 The saturation point varies slightly according to the tem- 

 perature of the water, warm water dissolving slightly more 

 salt than cold. The specific gravity of brine having 2G per 

 cent of salt is 1'2. These numbers are nearly accurate, and 

 easily remembered, though roughly we may adopt the 

 Cheshire formula for saturated brine, viz. : 1 part salt, 3 

 parts water. In the process of solution the salt is dissolved 

 and the clay is left behind. The surface of the salt is very 

 irregular when the saturation is completed, the masses of 

 clay remaining standing up in ridges or isolated miniature 

 mounds more or less honeycombed. The moment saturation 

 is complete no further action upon the salt takes place, and 

 however long the same body of water remains no further 

 dissolution of salt will occur. If, however, as nearly always 

 must happen, the water slowly evaporates, the salt held in 

 solution recrystallizes upon the salt surface below water and 

 forms a most beautiful crj^stalline floor or pavement, the 

 crystals of which form perfect semi-transparent cubes, 



* In becoming saturated, if it be deep enough to extend up the pillars 

 supporting the roof, it eats them away, and renders the mine insecure4 

 This was the case with Neumann's and Blackburne's mines, in Marston, 

 and to a slight extent with Gibson's mine, in Wincham. 



