288 DESCRIPTION OF THE MUSEUM. 



common salt., so useful in domestic economy. 

 The crystals are generally of a cubic form, as we 

 may observe in several specimens on the upper 

 shelves of the fifteenth case. Next to them is a 

 beautiful indigo blue crystal from Ischel,in Upper 

 Austria. The suite of varieties is continued in 

 the sixteenth case. Below the stage is the red 

 salt of Car dona, in Catalonia ; still lower is a 

 beautiful specimen of limpid muriate of soda, 

 from the celebrated mine of Wieliczka in Po- 

 land, one of the most important saltmines 

 known. It produces 120,000 cwt. of salt an- 

 nually, is 900 feet deep, and extends nearly six 

 miles in every direction. 



A considerable quantity of muriate of soda is 

 held in solution in sea water and certain lakes ; 

 being extracted by evaporation, it is then called 

 marine salt ; and it differs only from rocksalt, 

 because the latter is crystallized by nature. 



The muriate of soda, by dissolving, yields mu- 

 riatic acid, so usefully emplbyed in dying and 

 bleaching. 



The borate of soda, which comes next, is the 

 substance commonly called borax, or tinkal, and 

 comes from the East Indies ; it is purified before 

 it is used in the arts, and serves for soldering 

 metals and gilding jewellery. 



The carbonate of soda \yas formerly known 



