On the EffeEls of Terra Ponderoja. 609 



nion from that gentleman, both with regard to the 

 fufficiency, certainty and utility of thefe characters i 

 and I hope foon to fee the grounds of their diflent 

 clearly dated and fufficiently eftablifhed. 



However before fuch defcriptions can be carried 

 to that degree of perfedtion, to which the acute 

 obfervations and accurate diftinftions of a Werner^ 

 have raifed them amongft the Germans, it will be 

 neceflary both to adopt new words into our lan- 

 guage, and to fix more precifely and mineralogi- 

 cally the meaning of thofe we have already. 



On the Effects -produced by different Combina- 

 tions of the Terra Ponderofa given to Animals ; 

 hy Mr. James Watt, jun. 



READ NOVEMBER I3, I789. 



AT the Time of writing the foregoing Paper, 

 I confulted Dr. Leigh's Natural Hijiory of 

 Lancafhirey ChefhirCy ^c. in hopes of meeting with 

 fomething illuftrative of the Antiquity of the 

 Mine of Anglezark, and, though deceived in my 

 cxpedations in that refped, I was much ftruck 

 with a curious paffage, which feemed to point 

 out fome remarkable properties of the Aerated 

 Barytes unnoticed by later Writers. It is as 

 follows. 

 Vol. III. R r « There 



