26 



manufacture goes on that this trust in the sandstone m ay- 

 pro ve safe, but as it is not solid sandstone, but, according 

 to the section given by Mr. Bell, sandstone with layers of 

 marl at intervals, it is not well to put too great trust in it. 

 The longer the pumping continues — if any large quantity 

 of salt is abstracted — the more dangerous and destructive 

 will the subsidence be when it does occur. 



Although this method of mining by water let down a 

 pipe is comparatively modern, yet the action of water on 

 salt beds has been taken advantage of in Austria in the 

 Salzkammergut for obtaining the salt. I give an epitome 

 of what Dr. Schleiden says in his work, Das Salz. Referring 

 to Aussee, he says " the peculiar nature of this salt mountain 

 demands a special method of working it. It is not advan- 

 tageous to search for and hew out the scattered small 

 masses of rock salt, therefore they get the salt by so-called 

 Sinkwerks (or artificial salt lakes in salt mines). They 

 make large chambers in the mountain and allow them to fill 

 with natural water or convey it to them artificially. It 

 remains until it is saturated. The bottom of the chamber 

 is not thoroughly dissolved because the saturated brine 

 which rests upon it can take up no more salt. The side walls 

 are attacked by the water, and this attack is encouraged, and 

 the salt is rapidly dissolved in the roof as soon as the water 

 touches it, but this is not usually allowed or else the roof 

 would soon fall into the pit. The brine thus formed in 

 these ' sinkwerks ' is led by pipes to the salt works," 



A similar method is employed at Diirrenberg, in Saxony, 

 where the rock salt is much mixed with clay; but very 

 elaborate precautions are taken to prevent mischief arising 

 from this method of mining rock salt by fresh water. 



At North wich it has not been found necessary to put 



