48o 



occur, and more frequently by the ftrata themfclves baffeting en the fidtJ 

 and fummits of the mountains. 



In the whole of our extenfive bafalt country, I have met with but 

 one fpot in which this fubftance is not regularly ftratified, namely Car- 

 rickarede, where for about 200 or 300 yards, the bafalt precipice feems one 

 folid mafs. 



There is a circumftance attending bafalt, which much increafes my 

 allonifliment at hearing it clalTed among unftratified fubftances, that is, 

 it feems to be the only fpecies of rock whofe arrangement in ftrata 

 difcovers itfelf to the eye at all dillances. The contrafl: between our 

 bafalt and fchistus mountains is every where moft flriking, and the dif- 

 ference chiefly arifes from the ftratified arrangement of the bafalt. 



I think it pofTible a fkilful naturalift, who had given his attention to 

 this point, would, in failing along a newly difcovered coaft, be able to 

 pronounce on the materials of the mountains as he pafled them, merely 

 by their diftant outlines ; my experience has been too limited to permit 

 me to proceed farther with this topic, I only fuggeft it to naturalifts, 

 who may have opportunities to make fuch obfervations. 



The reader will probably be furprifed to find Mr. Playfair pcrfeftly 

 acquainted with this natural arrangement of bafalt, and ready to make his 

 ufe of it, in his controverfy with the •uoJcaniJls, who claim his tvhynjione 

 as their eruptive lava ; and that ftratification is one of the charafterif- 

 tlc mafks, by which he diftinguiflies his unenipted lava from their erupted. 



He fays, (feftion 236) " There are other marks that diftinguifli the lavas 

 " which we fuppofe to have flowed in the mineral regions, from thofe 

 " which aftnally flowed upon the furface — the phyfical geography of whyn- 

 " ftone countries, unlike in many refpefls to that of volcanic countries ; the 

 " fliape of whyn-ftone hills; their large flat terraces rifing above one ano- 

 " ther ; their perpendicular faces." 



I fee now that the natural arrangement of bafalt, in Mr. riayfair\ coun- 

 try and mine, is precifely the fame ; for what are large, fat terraces, rifing 



one 



