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HUTTONIAN THEORY. 



325 



furrows on the furface of the cryftal, very re- 

 gularly difpofed, and parallel to one another, 

 being without doubt impreffions from the thin 

 plates of the feltfpar, which furrcunded the 

 cryftal, and llightly indented it. They very 

 much refemble fome impreffions, remarked by 

 Pr Hutton in the granite of Portfoy, and afcri- 

 bed by him alfo to a fimilar caufe. He has re- 

 prefented thefe in his Theory of the Earth, 

 vol. i. plate 2. fig. 4. The adion and read:ion 

 of two cryftallizing bodies, hardly admits of a 

 ftronger and more unequivocal expreffion, than 

 in thefe tw^o inftances. 



Where the granite was little decompofed, 

 the quartz was not eafily difengaged from the 

 mafs it was imbedded in, and often broke in pie- 

 ces before it could be extricated. The cryflalli- 

 zation of the quartz, therefore, would not hav^ 



H 



been difcovered, but for the decompofition of 

 the feltfpar; and it is probable, that fimilar 

 cryfl;allizations exift in many granites where 

 they are not perceived. 



291. Some mineralogifl:s are inclined to think, 



that the regular cryfi:alli7-ation of quartz is to be 

 found only in what they call fecondary granites, 

 or in thofe that are of a formation fubfequent to 

 the great mafi^es which confl:itute the granite. 



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mountains. It is indeed true, that in the in- 



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fl:ances 



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