ITALY. LE T T E R XI. l$ 



pulation of making alum at the Solfatara. The 

 lead-pans laft for a hundred years and more. 



There is in fome parts of Solfatara fome 

 native green iron-vitriol, but in no confiderable 

 quantity. If they expofed to the acid fleams of 

 Solfatara iron-filings, or the iron-fand, which is 

 Ib common on the more from Naples to Pozzuolo^ 

 they would probably produce larger quantities of 

 iron-vitriol, and at a cheaper rate. By a fimilar 

 operation they might produce copper-vitriol by 

 copper-filings. 



Selenite is found on the inclofing walls of Solfa- 

 tara^ either in undetermined lumps or formed like 

 ftalactites. Being often grown in feather-like 

 fibres, ignorant Mineralogifts call it alumen flu- 

 mofum. 



In former times they gathered the fulphur-flow- 

 ers or lumps from the furface of the clay-heaps 

 accumulated near the (teaming fiflures, and dif- 

 tilled them in earthen retorts, which they had fent 

 from Rome ; but, the operations being too expen- 

 five, they have dropt it. 



Small cryftals of red arfemc, native fulpbur^ and 

 alum, do likewife fublimate on the furface of thefe 

 clay-heaps or the inclofing walls, either in fmall 

 lumps or lamelles, and many different fmall cryf- 

 talline forms. 



There 



