( 212 ) 



and I have obferved that many amorphous 

 lavas on the fhores of feveral of the Eolian 

 iflands are more compact than the prifmatic 

 lavas of Felicuda. 



What then can be the intrinfic circum- 

 ftance of the lava vv^hlch determines it thus 

 to cleave in the prifmatic form ? I confefs 

 I am ignorant : and who can fay that we 

 do not feek it in vain within the lava, 

 ilnce it may be extrinlic and adventitious ? 

 Such, certainly, appears to be the opinion 

 of M. de Luc ; and, more exprefsly, that 

 of M. Dolomieu, who, to explain the 

 phenomenon of volcanic prifms, has re- 

 courfe to a fudden congelation, and inflan- 

 taneous contraction of lavas. 



The fadls which we have adduced re- 

 lative to lavas, both prifmatic and not 

 prifmatic, it has been feen, do not always 

 accord with thofe related by the French 

 naturalift. But even on this fuppofition, 

 which is inconteftable, may we not retain 

 the fame principle of explanation, which, 



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