158 



sark in Lancashire only, but has since been observed at 

 several other places. 



Carbonate of barytes, it appears, was first discovered by 

 Dr. Withering (see Phil. Trans, for 1784, 301.), when it 

 was called aerated barytes; but Mr. Werner, wishing 

 to honour Dr. Withering for his abilities and accuracy, 

 named it Witherite. It has since very properly been called 

 carbonate of barytes. Radiating carbonate of barytes, in 

 its weight and appearance, very much resembles carbonate 

 of strontia : however, it differs from it in never being of a 

 greenish colour, and in having its radii larger, more com- 

 pact, and natter. 



The upper figure represents carbonate of barytes in dode- 

 caedral crystals, formed of two hexaedral pyramids joined 

 base to base, like quartz. 



These are the largest I have seen, and are very rare at pre- 

 sent. They are covered with a light ochraceous substance, 

 perhaps calamine. The matrix is carbonate of barytes, in part 

 decomposed, and of a chalky appearance. The figures below 

 show the geometrical plan, and in what manner one of the 

 solid angles of the base has been mistaken for part of an oc- 

 taedron, or has given the idea of two four-sided pyramids 

 joined base to base, which many have described as one of its 

 forms of crystallization. 



