149 



sure, dilate the prismatic hues, so that one or two sets may 

 take place of the 5 sets represented. 



We received this specimen from Durham, by favour of 

 Messrs. Harriman and Oliver, some few years since — but 

 did not know how valuable it was until lately — having now 

 discovered that it contains many small drops of water or 

 some other liquid in little hollows, which as far as we know 

 have never been discovered in any other substance except 

 quartz, or rock crystal. 



The lower one is another fragment with a curious pearly 

 appearance, and has somewhat the appearance of sulphate 

 of lime or gyps, but may be readily discovered by the 

 weight. 



TAB. LXXIL 



Tabui<ar sulphate of barytes is the most common 

 variety. The finest specimens generally come from the 

 neighbourhood of Cumberland. 



The tabular crystals are sometimes transparent, and 

 often more or less stained with ochre ; they mostly stand 



