( 2" ) 



"i5to polyhedrous pieces ; but when the 

 water pafTed through chalk, or calcareous 

 marie, the greater part of the pieces were 

 amorphous. When we however obferve lavas 

 with requifite attention, this conformation 

 in them feems to be efFed:ed differently. 



It has already been faid, that feveral of 

 the prifmatic lavas of Felicuda have for 

 their bafe fhoerl in mafs ; but it is true 

 that other congenerous lavas of the fame 

 ifland, which form as it were walls per- 

 pendicular to the fea, are fmooth over their 

 whole fuperficies. A firailar fmoothnefs 

 is obfervable in fome of thofe of Mount 

 Etna, on the fliore between Meffina and 

 Catania, w^hich have for their bafe the 

 horn-ftone ; though others extremely re- 

 fembling them, between Jaci Reale and 

 Catania, are formed in prifms. 



Compa£lnefs and folidity are, like wife, 

 not a neceffary condition in lavas, to this 

 appropriate cryftallization. This has al- 

 ready been remarked by M. Doloraieu ; 

 P 2 and 



