( 219 ) 



whether that Jire ivas vclcmiic or 7iot^—^ 

 Pojfibility of being equally deceived by pro- 

 dun'ions truly volcanic but erratic — Proof 

 of this from a clrcumfance which hap- 

 pened to the author — Little credit to be 

 given to accounts intended to prove the ex- 

 Ifience of ancient volcanos — NeceJJity that 

 fuch accounts fhould be lithologlcally dc^ 

 tailed — In ivhat manner our judgments 

 relative to lavas may be frequently mif- 

 iaken — Volcanic rocks may have the inoft 

 fpe clous appearances of lavas ^ though they 

 never formed currents — When other proofs 

 are vnafitlng^ cellulofity the mofl certain in- 

 dication (hat volcanic rocks have flowed in 

 a fiream — This cellulofty found In many 

 Eugatiean lavas — Singularity of the felt- 

 fpars of a lava near Rua^ which have^ 

 almoft ally a portion cf that lava for their 

 central nucleus — Lavas of GalzlgJiano^ 

 Plgozfzo, Monte Nuovp^ Monfellce^ a?id 

 Arqua — -Singular lava of Monte Nuovo 

 coinalnhig fcltfpars become earth ; and an- 

 other at Monfellce contaijihig pumices — 

 Lavas cf Catajoy one of isohlch forms co- 

 lumnar 



