ITALY. LETTER XVII. 2j7 



fimilar to the changed lavas in the So/fatara near 

 Pozzuolo. Elixiviated, it would, in all probabi- 

 lity, yield the fame alum. The red argillaceous 

 flone feems to be produced by lava, more affected 

 by the fulphureous acid, and by a difiblution of 

 the iron particles into a colcothar or crocus martis. 

 A great quantity of fulphur fweats, or evaporates, 

 from the diffolved white lava or this lava-clay. 



Somewhat further to the left, is a hot boiling 

 fpring, which depoles a glutinous fediment hard- 

 ening in the air ; and both the pool, and this 

 fpring, are called / Pantandli di Viterbo^ a popular 

 denomination, the origin of which I could not 

 make out. 



C. Fmm Monte Fiafcone to Acqua -pendent e. r. 

 Grey, hard and compact lava, with black and 

 green tranfparent flierl pebbles, fimilar to dark- 

 green cryfolites. Some topaz-coloured. 2. Grey 

 compact lava, with white oblong columnar fherl 

 or ftangen-fpath. 3. Detached (lones ferrumi- 

 iiated of black and green fherl with mica. 4. 

 Grey-yellow tufo hills alternating, 5. With red, 

 white, and grey fprinkled lava, containing black 

 and greenifh fherl-pcbbles ; a fingular fpecies of 

 lava. The red fpots are tile-coloured, friable, 

 unaffected by acids, either argillaceous or indu- 

 rated puzzolana. The grey afhes (4) alternate 

 like wife 6. with grey, hard, and compact lava, 



7. with 



