.1 



484 



in our filiclous bafalt, and in a lefler degree In the coarfe bafalt con- 

 tiguous to it. 



I have, it is true, found one or two detached pieces lamellated, 

 (they had been long expofed,) but nothing fimilar ever occurred 

 in the original ftrata, nor have I met with a Cngle particle of 

 fchiftus in the whole extenfive bafaltic area : Schiftus too is gene- 

 rally refractory, while the filicious bafalt is eafily fufed and vitri- 

 fied, and in its conchoidal frafture it more refembles bafalt than 

 fchiftus. 



The flrongeft argument feems to be deduced from its grain, 

 which may be traced in different fpecimens (in any of the col- 

 ledions I have given to Dr. Hope or our own Mufaea) pafiing 

 from the likenefs of jafper or filex, by infenfible fhades, until its 

 grain approaches to, and then becomes coarfer and more granular, 

 than the Giant's Caufeway bafak. 



I hope Sir Jamts Hall will be induced to analyfe this ftone ; if 

 he then fliall pronounce it not to be bafalt, I venture to predift 

 it will be among the Jilicms, and not the fchiftofe tribe he will 

 clafs it. 



Whatever may be finally decided as to its clafs, its arrangement 

 with that of the contiguous bafalt at Portrufli and its iflands, 

 are fatal to a favourite poiition ftrenuoufly infifled on by the Plu- 

 tonifts, to wit, " That their fufed unerupted bafalt has been forced 

 " up from the fubterranean regions, and violently injeded between 

 " ftrata of other materials, by which their alternations with thefe 

 " ftrata are formed." 



Thus Mr. Whitehead accounts for the alternate ftrata of limeftone 

 and toadftone {bafalt) of which part of Derbyfiire is formed, to 

 the greateft depths human induftry can penetrate ; he even flatters 

 himfelf fo far as to think, he had difcovered the funnel by which 

 the fluid lava had paffed up from the centre of the earth. 



In 



