105 



TAB. CCCLVII. 



Steatitic Pitchstone. 



I was favoured with the present specimen from a vale neat 

 Clowance Park, in Cornwall, by Phil. Rashleigh, Esq. 

 The outer white parts are said to be Tungstate of Lime, 

 a very rare substance in Great Britain : there are also 

 some Asbestus and Ruby Copper about it. One great cu- 

 riosity attendant upon these substances is, that they natu- 

 rally contain an Alkali, which formerly used only to be pro- 

 cured from vegetables : the great discovery of the basis of 

 Potash and Soda, made by Mr. Davy, has thrown a great 

 light on these and other substances, as to their changes and 

 appearances, which we need no longer esteem positively 

 volcanic ; since the powerful agency of motion, with the at- 

 traction of these bases for oxygen, may give an effect which 

 We here see to be analogous to the power of a glass-house 

 furnace. These discoveries thus become of much more 

 consequence, as they lead towards the elucidation of what 

 we were before totally ignorant of. 



The fracture is more or less conchoidal, like Pitch. It 

 is as hard as Quartz and nearly as brittle as Glass j and, 



