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hiilory, have conllantly experienced two 

 effects in their congelation. Thofe which 

 have cooled in the air, have divided, in 

 confequcnce of the contradion they have fuf- 

 fered by the lofs of their caloric (heat , into 

 irregular mafles ; while aK the others, which 

 have precipitated into the fea, have, on their 

 fudden congelation, contracted in a regular 

 form, and divided into prifmatic columns, 

 which form they have only taken in the 

 parts in contact with the water of the fea. Of 

 this he met with evident proofs along the 

 fhore which extends from Catania to Caftello 

 di Jaci ; and the famous lava of 1669, though 

 unapt to the prifmatic form, from being 

 fpungy and little in qMr-ntity, yet in fome parts 

 exhibits a kind of rude imperfed; prifms. 



Among the objeds to which I was at- 

 tentive in my volcanic travels through the 

 two Sicilies, the prifmatic lavas were cer- 

 tainly not the lad. While making the cir- 

 cuit or the Eolian iflands, of Etna and of 

 Ifchia, 1 conftantly obferved carefully the 

 CQnformatlcn of the flony currents which 



fall 



