SALT WORKS. 77 



SUBTERRANEAN SALT WORKS. 



BY PROF. CHAS. A. HAY, OF GETTYSBURG. 



That jaunt of three miles in the heart of the Durrenberg revealed 

 to us the manner in which the brine is procured from which the Austri- 

 ans manufacture their salt. Chambers are excavated in the salt rock, in- 

 to which pipes are introduced from above. Through these fresh water 

 is let into the chambers until they are filled to the ceiling. At once the 

 rock, which is composed of clay, or marl, or gypsum, intermingled with 

 and saturated by the salt, begins to crumble away from the sides and 

 roof, the salt being dissolved, and the earthy matter falling upon the floor 

 of the chamber. This process is allowed to continue until the water 

 has gained twenty-six per cent, of salt, when it is tapped ofi" by pipes 

 leading through ihe lower shafts of the mine outward to the side of the 

 mountain and down into the valley where it is evaporated. As soon as 

 these chambers have been emptied of their brine, the floor, now strewed 

 with what had fallen from the ceiling, is spread over with a layer of 

 pounded clay, and fresh water is again introduced from above. This 

 immediately attacks the surrounding rock, and removes again between 

 one and two feet from the sides and ceiling before it gains its required 

 percentage of salt. The time necessary for it to acquire this degree of 

 saltness varies in the difi'erent mines. Here, at Hallein, a few weeks suf- 

 fices, at some others months are required, and at Hall (Aust.) a whole year. 



It will at once be seen that these dissolving chambers must be con- 

 stantly rising in the mountain and spreading out horizontally. And it 

 is a singular tact that the mass of rubbish that collects upon the floor, 

 and that subsequently forms the roof of other chambers that work their 

 way up from below, becomes saturated again with salt and capable of 

 furnishing a new supply. 



Dreadful accidents sometimes occur in these mines. The water 

 from one chamber, eating its way through the rock, sometimes finds its 

 way into another in which the workmen are engaged, and great loss of 

 lii'e ensues. Sometimes the roof falls in and two chambers are thus 

 thrown into one. No one can wonder at this, for some of the chambers 

 are five and six hundred yards in ciixumference, with not a single sup- 

 port for the rocky ceiling. When they have spread to so large a size 

 they are generally deserted, or left, half full of water, to be visited by 

 the curious. The one we sailed through, and which had been so bril- 

 liantly illuminated for our gratification, was certainly larger still. The 

 statistical account of the mine gives the dimensions of this chamber as 

 fifty-five fathoms and six feet long, and twenty-eight fathoms and five 

 feet broad. 1 do not know the precise value of the Salzberg falhoin, 



