478 



With Dr. Huttm, bafalt or whynn is a lava flowing in the bowels 

 of the earth, driven upwards by fome powerful agent ; forced into 

 the fiffures and crevices of the ftrata, and fometimes iinpelled with 

 fuch violence between parallel ftrata as to feparate thenri ffom each 

 other, and to lodge between them. 



That this fubftance, out of the reach of our ambient air, and 

 afted upon by incalculable preffure, poflefles many properties totally 

 different from thofe of common erupted lava.f 



When Dr. Huiton and Mr. Piayfair pronounce fo politively, that 

 bafalt is fubterranean lava, they do not attempt to enter into any 

 proof that it ever was in fufion ; they content themfelves with de- 

 nying to it fuch properties, as are obvioufly incompatible with the 

 origin they give it. 



Stratification is one of thefe; for it is clear from their own ac- 

 count of this fubftance, that it could not be arranged in Strata ; 

 Dr. Button, therefore, makes a grand diftinclion between ftratified 

 and unjiratified bodies ; of the latter, all he enumerates are granite, 

 porphyry and bafalt, or whynn. 



As I am not acquainted with granitic countries, I can throw no 

 light upon this part of the fubject ; I fhall only obferve, that the 

 ftratification of granite, is maintained by Pallas, De Luc and Saujfure ; 

 even Mr. Piayfair himfelf feems to give it up. 



Porphyry, Mr. Piayfair tells us, (feclion 76) is a variety of whynn ; 

 the whynnfione of the old world. He forgets, however, to tell us 



how 

 - f That bafalt is often found as defcribed by Mr. Piayfair, cannot bt denied ; it alter- 

 nates with calcareous ftrata, in many places, though in our extenfive bafalt country it mixes 

 with it (and that flightly) but in one fpot, Kenhaan. Its arrangement over the world 

 fteras to be in accumulations of extenfive, parallel ftrata, covering the furface of the earth ; 

 fo, at leaft, our whole bafaltic country is covered. Of fuch arrangement, Mr. Piayfair takes 

 not the leaft notice ; it is, indeed, fata) to his fyftem, at firft glance ; for, exclufive of the 

 impofTibility of difpofing his lava in regular ftrata, yet, admitting it was done, his unerupled 

 lava, now is become erupted, and being fpread on our furface, e.xpofed to the air, and re- 

 lieved from prejfure, Hiould poffefs all the properties of common volcanic lava, derived, by 

 his account, from the fame fource ; but he labours to fiiew, that important differences d* 

 »cd ou^U to exift between them. 



