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HUTTONIAN THEORY. 



275 



fyllem, fhould now appear equally ft 



nuous in defence of the Neptunian. Though 

 Dolomieu contends for the volcanic origin of 



foine bafalt 



r 



rocks, he does not admit that all 



bafultes is volcanic, nor even all of igneous for- 

 mation. Thus he ftates, that he had examined 

 at Rome fome of the molt ancient monuments 



r 



cfart, executed in bafaJtes, brought from Upper 



Egypt, 



the ad 



d that he could difcover 



of fi 



in any of them 



trary, he found that fome of them 



niark of 



On the 

 confift- 



ed of green bafaltes, which changes its colour 



when expofed even to a mo- 



to a bronze 

 derate heat, 



can never hj 

 fire. 



d 



hich therefore, h 



endured any i];rong ad 



g 



of 



The anfwer to this argument is very plain, if 

 we admit the efFeds afcribed by Dr Hutton to 

 the corapreffion which neceflarily takes place in 

 the mineral regions. If indeed the heat in thofe 



regions refemhled exadly that of our fires 



at 



the furface, it would not be eafy to deny the 

 above conclufion, which therefore certainly 

 holds good againft the volcanic origin of the 



Egyptian bafaltes. 



But there is no i:eafon why. 



under ftrong comprefljon, the colouring matter 



S2 



of 



* 



Journal de Phyfic^ue, tome xxxvii. ^.. /90.) partie 2^ 



P*i93- 



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