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made by Mr. BefTon in Limoges, 29 Roz. Tour, p. 89, for he 

 difcovered veins of granite in an argillite, though this fchift did 

 not border upon any granitic mafs, and hence he judged it of 

 modern formation. Citizen Dolomieu alfo tells us that fuch in- 

 ftances had occurred to him in his travels, but lie thinks them 

 perfedly diflindl from the granite which forms granitic mountains, 

 16 Journ. des Mines, p. 22. Neither was Sauffure a flranger to 

 fuch granitic veins, but he accounts for their origin very diiierently 

 from Sir James, § 600. 



Various attempts have^been made to fufc granitoe, in mofl of 

 which, as has already been faid, felfpar is the moft abundant ingre- 

 dient, but in almoft all, though finely pulverized, the quartz remained 

 ■unfufed and might be diftinguhhed by a lens, fee i SaufTure, 

 §. 172, 173 and 174, I Gerh. Gefch. §.51, and in the firft part 

 of his new mineral fyftem publilhed in 1797, p. 412, and 

 Hacquet in i Crell Beytrage, p. 34, 35, &c. It is plain then, 

 that in all heats with which we are acquainted the felfpar cannot, 

 butin very rare cafes ferve as a flux or a menflruum to the quartz 

 with which it is found in granites, the full proportion of quartz 

 which can be rendered fufible by its other component earths being 

 already contained in the felfpar, and in fad there is no analogy 

 betwixt water adling as a menflruum on fait, and felfpar adf ing on 

 quartz, for water and fait are fubflances perfectly heterogeneous to 

 each other, whereas felfpar and quartz are both earthy fubilances of 



which 



