236 THEORY of the EARTH. 



but, by aqueous folution, this particular combination is again 

 refolved, and forms an acido-metallic, that is, a vitriolic fub- 

 ftance, after the phlogifton (which refufes aqueous folution) has 

 been feparated from the compofition, by means of the joint 

 operation of vital air. 



THE variety of thefe fulphureo-metallic fubftances, in point 

 of compofition, is almoft indefinite ; but, unlefs they were all 

 foluble in water, this could not have happened by the action of 

 that folvent. If we mail allow any one of thofe bodies to have 

 been formed by the fluidity of heat, they muft all have been 

 formed in the fame manner j for there is fuch a chain of con- 

 nection among thofe bodies in the mineral regions, that they 

 muft all have been compofed, either, on the one hand, by 

 aqueous folution, or, on the other, by means of heat and fu- 

 fion. 



HERE, for example, are cryftallized together in one mafs, 

 firft, Pyrites, containing fulphur, iron, copper ; 'idly, Blend^ 

 a compofition of iron, fulphur, and calamine j 3^, Galena, 

 confiding of lead and fulphur ; ^tbly, Marmor metallicum, being 

 the terra ponderofa, faturated with the vitriolic acid j a fub- 

 flance infoluble in water ; 5//y, Fluor, a faturation of calcare- 

 ous earth, with a peculiar acid, called the acid of fpar, alfo in- 

 foluble in water j bthly, Calcareous fpar, of different kinds, be- 

 ing calcareous earth faturated with fixed air, and fomething 

 befides, which forms a variety in this fubftance ; laftly^ Siliceous 

 fub/lance, or Quartz cryjlals. All thefe bodies, each poflefling 

 its proper fhape, are mixed in fuch a manner as it would be end- 

 lefs to defcribe, but which may be expreffed in general by fay- 

 ing, that they are mutually contained in, and contain each 

 other. 



UNLESS, therefore, every one of thefe different fub fiances 

 may be diffolved in water, and cryftallized from it, it is in 

 vain to look for the explanation of thefe appearances in the ope- 

 rations of nature, by the means of aqueous folution. 



ON 



