PREFACE; *. XI I lie thif J clafs comprehends the combuftible fub- Rances, with the exception of the metals. It is fub- divided into two orders. i. Simple combuftibles. 2 - Compound combuflibles. I he fourth clafs includes all the different metallic minerals. It is fubdivided into three orders, i. Con tains metals not oxydable by heat. 2. Thofe which are reducible and oxydable by heat. 3. Metals which are oxydable, but not reducible by heat. 1 hefe four claffes are follotved by three appendices In the firft appendix is contained all doubtful or un- afcertained minerals. The fecond includes all the cbmpound rocks. It is fubdivided into three orders: the firR contains primitive rocks; the fecond, the fe- condary and tertiary rocks ; the third, aggregates formed by the agglutination of fragments- I he third appendix is dedicated to volcanic pro- 10ns. It is fubdivided into fix claffes. i. Con tains lavas. 2. Tbermamides. 3. Produfts of fub- hmation. 4. Altered lavas. 5. Volcanic tufas, and Suoftances which have been formed in lava after their eruption, and cooling. ^ In tab fyffem the arrangement of fimple minerals a mod ffridly chemical; but the arrangemefit and ^ cnption of the rocks and lavas is founded on cer- tll ‘ciful ideas refpecting their formation, and is I- ^ tT1 f I ^ exec i ll tcd; but an examination of this part \ ^ > f £l,n ^ e ^ on g s properly to geognofie. te pecics of fimple minerals is determined from ne c t racer, which is ftyled the integral mollecule. auy defines the mineral fpecies to be “ Une ed it 2 “ lection