Hock Salt at Cardona in Spain. 55 



The almost total absence of vegetation on the mountain 

 facilitates the study of its composition and structure ; it will 

 not be useless to add, that M. Cordier visited this place in 

 the best season for observation, that is, at the beginning of 

 winter. 



These first data being laid down, we shall enumerate the 

 rocks composing the mountain : they may be arranged in six 

 principal divisions, viz. 



1. Rock of perfectly pure muriate of soda, very large 

 grained, semi-transparent, and colourless. The grains are 

 quite clear; some are found so large, that, by mechanical 

 division, cubes of two decimetres ^nearlySin.] may be 

 formed. 



2. Pure muriate of soda, the mass sraalt grained, more or 

 less translucent. Its principal colours are greyish white, 

 pearl grey, reddish white, flesh red, wine lee red, and brown- 

 ish red. 



3. Impure muriate of soda, mass granular, which would 

 enter into the preceding division, were it not mixed more or 

 less abundantly with either grey or blueish clay, or with 

 very small white or reddish crystals of common gypsum. 

 This last mixture gives a porphyritic structure to the mass. 



4. Grey or bluish clay ; it is sometimes pure and slightly 

 schistose, at others porphyritic from the mixture of a great 

 quantity of small common gypsum crystals, that are some- 

 times grey and opaque, at others colourless and transparent. 



5. Common gypsum, the mass small grained; it is opaque; 

 its white colour often approaches grey or yellowish : clay- 

 disseminated in small quantities is occasionally found in it. 

 Some small rare grains of grey lamellar carbonate of lime 

 also occur. 



C. Common gypsum, mixed with anhydrous gypsum ; the 

 mass is granular passing into compact ; this kind in other 

 respects resembles the preceding. 



Tliese diflFerent materials occur in very unequal propor- 

 tions. The small grained pure muriate of soda (No. 2) may 

 be estimated alone to form seven-tenths of the mountain. 

 The impure muriate of soda and clay each constitute about 



