ON A NATURAL SYSTEM 



5 xci. Four Genera ofFofft/s mixed mechanically. 



ANSWERING this clcfcripiion, we have four 

 genera only, which arc denominated according 

 to the clafs of the molt predominant ingredient 

 in their compoiitiun. 



} xcn. Flrjl Genus. 



THE firft genus in which the fulinc charac- 

 tcr prevails occurs fometinies in the neighbour- 

 hood of volcanoes. In gyp I inn alto other foflils 

 intimately mixed arc occafiorially found. The 

 fubflunces likcwifc contained in natural waters 

 may perhaps be referred to this genus. They 

 are indeed held by water in folutioii, but their 

 union is generally merely mechanical, of which 

 the fixed principles arc collected in the reildua, 

 after .the evaporation of the liquor. 



} x c n I . Second Genus. 



To the fecond genus we uflign allthofe foflils 

 in which the earthy principle abounds. Such 

 are thofe placed by Cronfledt in his full appen- 

 dix under the name of J}t\a. Under this ge- 

 nus may be arranged fcveral matrices of metals 

 as well as of inflammable Jubilances; for lithan- 



* . thrax, 



