ON A NATURAL SYSTEM 



by the name of Agaric. Larger mattes however 

 of calcareous powder, expofed for many years 

 to the prciTiirc of a confidcrable weight, acquire 

 at length fuch a degree of confillence, that di- 

 flinft lines can be drawn with fmall pieces of 

 them; indeed this property b found in calca- 

 reous chalk likcwife. Hitherto the greater de- 

 gree of liardncfs has been produced by cry- 

 ftallization, as we find that calcareous cryitals 

 make no mark whatever, a circumstance ouing 

 to the firm union of their particles, by which 

 the friction on a painter's canvaf> has no eilect 

 upon them, at leail fo as to be viiiblc. 



What has been thus briefly dated may be 

 fuflicient to fatisfy us, that, from the external 

 qualities of follils, no proper judgement can be 

 formed of their internal compoiition. 



OF THE SEVERAL CRITERIA OF FOSSILS. 



x I x. Oryflology. 



OKYCTOLOGY, or Mineralogy, are names giv- 

 en to that fcience, which fo arranges all the 

 known foilils, that they may be accurately di- 

 ilinguiflied from each other. 



I 



