Calcareous Genus. 27 



Agaric Mineral, Guhr. 



This fanciful name denotes only a loofe 

 Calcareous Earth found in the clefts or cavi- 

 ties of rocks, moftly white, but fometimes 

 red or yellow, from a mixture of clay or 

 ochre. 



Chalk, Craie, fyaie de Champagne^ blanc 

 d Efpagne of the French. 



This fubftance is too well known to need 

 any defcription, the pureft is iv&tte, yet it 

 contains a little filiceous Earth, and about 

 two per cent, of argill. Mr. Rinmaris Hiftory 

 of Iron, 201, mentions a blue chalk found 

 in the ' neighbourhood of Upfal, which con- 

 tains iron. Mr. Beaume fays that the pureft 

 calcareous Earths he has met with contain 

 fome fmall proportion of iron, which depofits 

 from fokitions long made, i Beaume 255. 

 however I have frequently ufed chalk, in 

 whofe folution neither galls nor Pruffian alkali 

 could difcover any. Dry chalk contains 

 more aerial acid than any other of the cal- 

 careous clafs ; generally about forty per cent, 

 jts fpecific gravity is from 2,4, to 2,65. 



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