435 



From an attentive confideration of Mr. DolomUa's catalogue of the 

 volcanic produflions of Etna, (republiflied by Mr. St. Fond) and the 

 accurate and minute account it gives of the flrata of the country ("cur- 

 rents of lava Mr. Doloinieu generally calls them) I have long been 

 induced to think, that Sicily, in its original conftruftion, flrongly refera- 

 bled the bafaltic part of my own country, being, like it, compofed 

 of bafalt ftrata, often prifraatic and columnar, fometimes alternating 

 with calcareous llrata, and with others compofed of marine depofitions 

 and exuvise ; that in this ftate Etna erupted, and frequently covered 

 with its lavas and fcoria the preexifting bafaltic and marine ftrata. 



Converfing once on this fubject with my friend, Profeffor Pictet of 

 Geneva, he requefted me to put my fentimcnts on paper, that he 

 might communicate them to his friend Mr. Dolomieu: I did fo, and 

 aware that I was expofmg myfelf to a charge of prefumption, for dif- 

 cuffing the conflruftion and productions of a country I had never 

 feen, I limited myfelf rigidly to the fafts ftated, and admilTzons made 

 by Mr, Dolomieu himfelf; but, before my obfervations could reach 

 him, he was no more. Profeffor Pictet has fince publillied them, in his 

 Bibliotheque Britannique, No. 144. 



My conjecture, that many of the flrata of Sicily, though called by 

 M. Dolomieu currents of lava, were not actually fuch, has fince been 

 confirmed by obfervations made on the fpot by Sir James Hall, Bart. 

 a ilcilful naturalift, and able chemift, who firlt difcovered the mode of 

 fufing bafalt without vitrifying it, therefore little likely to be milta- 

 ken upon a bafaltic fubject. 



Sir James tells us in the tranfactions of the Royal Society of Edinburgh 

 " for the year 1799, " It is generally fuppofed, that fome lava.s of Etna con- 

 " tain calcareous fpar and zeolite ; but, this I conceive to be a miftake. It is 

 " true, as I have feen, that many rocks of Etna contain thefe fub- 

 " fiances in abundance ; but, in my opinion, thefe rocks are no !a- 

 " vas, but have flowed fubterraneoufly like our whins, and arc the 



Vol. XL ( 3 I ) fame 



