276 TRAVELS THROUGH 



produced by the conne&fon of the pyritical ful~ 

 phureous aeid with the calcareous earth. But, a 

 great quantity of talc-glimmer, and even many 

 pieces of Gabbro offering in this clay, whicii 

 befides is uncommonly fat and talcous to the touch, 

 there is no doubt of its containing a good deal of 

 talcous Gabbro or Serpentine-earth. Has not 

 therefore this clay a fhare in the compofition 

 of Gabbro or Serpentine ? Their natural affi- 

 nity of external qualities, and their now-defcribed 

 birth-place and fituation, together with the expe- 

 riments of Doctor Stange *, leem to countenance 

 this opinion and the generality of Mineralogifts, 

 who hitherto have ranked the Serpentine among 

 the argillaceous ftones. However, I am very well 

 acquainted with the experiments of the juftly cele- 

 brated Director Marggraf at Berlin -f- j according 

 to which the Gabbro or Serpentine contains a par- 

 ticular alkaline earth, the very fame which is vifi- 



* This gentleman is at prefent Profeflbr of Chemiftry at 

 W.urzburg, -and has publifhed his Experiments in a Differta- 

 tion printed at Franckford on the Oder. 



f See his Demonftration of the alkaline parts of common 

 fait being an alkaline fait. Tom. I. of his Chemical Works. 

 Analyfis of the evaporated brine and its earth. Ib. Tom. IT. 

 Experimental Demonftration of the Serpentine- ftones not 

 being of an argillaceous kind. Ib. Tom. II. Account of the 

 effefts of vitriolic acids on feveral fpecies of (tones and earths. 

 Ib. Tom. II. 



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