( ^9o ) 



Catajo, IS In no refpecl dliFerent from this, 

 except that the quartzofe grains are not 

 accompanied with green fpots. It yields 

 in the furnace the fame volcanic produdt. 



At Monte Niiovo we find feveral mafles 

 of a lava which deferves our notice, from 

 its being reduced to fuch a ftate that it is 

 pulverable by the mere prefllire of the fin- 

 ger. It has an argillaceous bafe, and con- 

 tains an abundance of feltipars v/hich have 

 preferved their prifmatic figure, but are ne- 

 verthelefs pulverable. It is rare, in volca- 

 nic places, to find feltfpars fo much injured, 

 even where they have been adted on by 

 fulphureous acids ; of which there are here 

 no traces; and therefore this decompofition 

 feems to be derivable from the humid ele- 

 ments, and other caufes in the atmofphere. 

 On breaking this lava we difcover fome 

 minute octagonal and hexagonal prifms, 

 obliquely truncated, lefs foft than the bafe 

 to which they are attached. They do not 

 in the leaft appertain to the genus of either 



fhoerls 



