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iJDay as by the humid — This exemplijied in 

 the generation of hafaltes — An ahufe of 

 analogy to conclude from it one common 

 origin of bafaltes — When examined de- 

 tached^ they frequently hear no peculiar 

 chara&er of their origin, ivhich mufl be 

 determined from local circumfaiices — jE";/- 

 quiry ivhether bafaltiform lavas have be- 

 come fuch by a fudden coridenfation ivithin 

 the fea — Proofs which fhew, fi^fl-i tk^^ 

 maity bafaltiform lavas have affumed this 

 fymmetrical co?fguratio7t on coagulation in 

 the waters cf the fea ; fecondly, that in 

 others it has taken place only by congelation 

 in the air ; thirdly, that very numerous 

 lavas have proved refraElory to this fgure, 

 both within the fea and in the air — The 

 property of affuming a prifmatic figure ap- 

 pears, in many lavas, not to depend on their 

 being of a particular fpecies, nor on their 

 compacinefs and foUdity, but on extrinfic 

 atid adventitious circumfances — Thefe cir^ 

 currfances indicated, ivith an explanation 

 in 'what manner, according to their pre- 

 fence or abfence, lavas frequently offume a 



prfmatic 



