^^ 



292 



ILLUSTRATIONS OF THE 



«T 



Now, what caufe can have determined the co 

 lumn of water, which refted on the bafe at prefent 

 occupied by this roclc, to depofite nothing but 

 the materials of whinftone, while the water on 

 the fouth, weft, and north, was depofiting the 

 materials of arenaceous and marly 'ftrata ? 

 Wherefore, within this fmall fpace, was the pre- 

 cipitate every where chemical^ to ufe the lan- 

 guage of Werner, while clofe to it, on either 

 fide, it was entirely mechanical? Why is there 

 in this cafe, no gradation ? and why is a mere 

 mathematical line the boundary between re- 

 gions where fuch different: laws have prevailed? 

 Whence alfo, we may afk, has the bafaltic de- 

 pofite been abruptly terminated toward the 

 weft, fo as to produce the fteep face which has 

 juft been mentioned ? The operation of currents, 

 or of any motion that can take place in a fluid 

 will furnifti no explanation whatever of thefe 

 phenomena ; yet they are phenomena far from 

 being peculiar to a fingle hill ; they are among 

 the moft general and charaderiftic appearances 

 in the natural hiftory of whinftone mountains ; 

 and a geological theory which does not account 

 for them, is hardly entitled to any confidera- 

 tion. 



256. The bafaltic rock, juft defcribed, is alfo 



coveredj at leaft partly, with ftrata perfedly fimi- 



lar 



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J V ' 



