406 Dr. Traill on the Salt Mines of Curdona, 



The channelled surface is evidently produced by the action of the 

 winter rains, which have given the whole a striking resemblance to 

 the surface of a mass of ice, which had been partially thawed and 

 again frozen. 



The general colour of the exposed surface is greyish white, with 

 here and there a tinge of pale reddish brown, from the colouring 

 matter of the superincumbent bed of clay. Towards the extremities 

 of the mass of salt, extremely thin layers of a pure and plastic clay 

 are insinuated between layers of salt, so as to give it the waved 

 delineations which often occur in some species of calcsinter. The 

 general mass of salt is however of the greatest purity ; and in order 

 to be converted Into snow white culinary salt requires no other 

 process but grinding. The greyish hue of the external surface is 

 owing to the rain penetrating a portion of the salt, and by diminish- 

 ing its opacity, depriving It of the whiteness which the fresh fracture 

 generally presents. At the period of my visit the surface of this 

 immense mass was perfectly dry, and in some places, where water 

 had most recently flowed, was covered with a snow white efflorescences 

 This circumstance, as well as the sharpness of the edges above- 

 mentioned, shew the little hygrometric water in the atmosphere of 

 that country, and the general purity of the salt from earthy muriates. 



The fracture of the salt is highly crystalline, and usually exhibits 

 large granular distinct concretions, which give it sometimes the 

 appearance of a breccia, or of containing imbedded crystals. 



A perennial brine spring flows at the foot of the great precipice, 

 and affords a strong proof of the little effect of water on this very 

 compact salt. The aperture through which the stream has issued 

 for many years, is not wider externally than two feet, and suddenly 

 contracts to a few inches ; while the channel worn in a solid floor 

 of salt, through which the stream has long flowed, is not a foot in 



