O F F O S S I L S. 153 



5 LXXXVIII. Pyrites and Molybdena do not con-* 

 Jlit ute peculiar Genera* 



I HAVE referred pyrites, or fulphuratcd iron to 

 the genus of iron. In like manner, molybdena, 

 \\hi-.h is nothing elfe than a metallic calx mi- 

 ncrali/cd by fulphur, provided its genus were 

 known, ought to be aflribcd to the clais of me- 

 tals. /\s to the foflil confidcrcd by Cronftedt as 

 fixed plilogidon, and which he calls brandertz t 

 its compntition lias not as yet been fufliciently 

 invciligated. 



LXXXIX. Properly f pea king, there is but one Ge- 

 nus ofpbhgijlic Subjlances. 



IN the flridncls of language, all the genera 

 of this clafs might be reduced to one, as the 

 fame principle of inflammability prevails in each 

 of them. 



xc. Firjl Appendix. 



iNthefirft appendix to the clafies, arc treated 

 thole foiftls of various and mechanical combina- 

 tion, and which for the mod part is obvious to 

 the fight. 



