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As the Whynn Dykes, Mr. Mills obferved, are uoqucftionably bafalt, 

 he calls them all lava, and attempts to prove it by a fort of vague in- 

 duftion ; page 75 he fays Iflay Whynn Dykes referable thofe at Bal, 

 lycaftle, which take their rife in a country confepdly abounding with vol. 



canic matter. 



Now the fpecimens from the Iflay Dykes ftrongly referable Cas he 

 fays) the Derbyfliire toadftone, formed, as he afferts (page 98), by fub. 

 terraneous fire. 



Of Derbylhire- I will not prefume to fay any thing, having never 

 vifited it, but the proof of its (Irata being lava, reds upon the adralffion 

 of Mr. Whitehurft's pofition, that thefe toadftone ftrata were formed by 

 fucceffive eruptions of a volcano at the centre of the earth, which pour- 

 ing up repeated torrents of liquid lava, thefe fpread when they approach- 

 ed the furface of the Earth at different difl:ances, and formed the toad- 



{tone ftrata. 



When Mr. Mills endeavours to cflablifh his opinions by aflertions re. 

 lative to my country, I will venture to reply to him. 



The precipice frora which the Whynn Dykes iffue at Ballycaftle, by 

 his own account, confifts of alternate ftrata of freeftone and coal, not very 

 like volcanic matters : and as to his pofitive and general affertion, that 

 our bafaltic country confejedly abounds with volcanic matters, I muft re, 

 ply in his own ftile, pofitively and generally, that it does not afford a 

 fmgle particle of volcanic matter ; that I have examined this trad for a 

 longer time, and probably with more attention than any other perfon 

 ever did, or I would not prefume to hazard the affertion fo confidently. 



When your Lordfliip is fo good as to perform the promife you made 

 me, of fpending fomc time with me at the Giants Caufeway, you will be 

 able to judge for yourfelf as to the truth of thefe contradiftory af. 

 fertions. 



The advocates for igneous operations over the furface of our globe 

 are fo prejudiced, that it is foraetiraes fufficient to refute thera merely 

 to quote their own words. As Mr. Mills's paper is now before 

 me, I will give your Lordftiip an inftance: he fays page 98. " In 



fhort. 



