New Publications. l6g 



or rarefiflion while it was diffused within them. The known 

 external caufes of the entire decompofition of ftony matters 

 are reprefented to be only water, carbon, and carbonic acid 

 gas, which enter into new combinations with the faline mat- 

 ters, the fulphur, the ferruginous oxyds, the manganefe, the 

 lime, and other conllituent parts of the ftones with which 

 they come into conta6l. 



Mountains are the fubjefts of the fixth of thefe Eflays. 

 The author defcribes the primiifve mountains as containing 

 within them no animal nor vegetable remains; as compofing 

 all the loftieft extremities of the earth ; as never covering nor 

 leaning upon thofe which are caWed Jt'condarj", as exilUng 

 fomctimes in ftrata, but oftener in huge rocks ; asvarioufly 

 compufcd, of granite and granitic compounds, gneifs, fchif- 

 tofe mica, filiceous fchilUis, bafanite, jafper, pitchftone, 

 hornblende, hornblende (late, indurated lithomarga, argil- 

 lite, trap, ferpcntine and potftone, porphyry, hornflate, 

 fchiftofe porphyry, fanddone, rubble-ftonc, farcilite, gra- 

 nular limeilone, marlite, gypfum, fluor, topaz-rock. Of 

 each of thefe forts of (lone he gives, in part, the mineralor 

 gical geography. The fecomhny mountains are next de- 

 fcribed by him, in the fame eflay, as being either marige- 

 rious or alluvial ; as containing in their flrufture var;ous re- 

 mains of animals and vegetables, terreftrial and aquatic ; as 

 always incumbent on primary n.cks, or inverting them; as 

 ftratified or columnar, unigenous or polyger.oiis ; as vari- 

 oufly compofed of limeftone, fwineftone, o^iform linieltone, 

 porous limeftone, marlites, and calcareous fancUtones, chalk, 

 g\-pfum, argillite, indurated clay, flialc, bituminous fliale, 

 Indurated lithoma'*ga. (late, argillaceous fandftone, porphyrv, 

 trap, and bafalt ; hornblende, argillaceous and calcareous 

 breccias, hornftonc, jafper, filiceous breccias and fi;iceous 

 fandftone. By an ample in.luftion of facls it is proved, ihat 

 all thefe different forts of ftone have been found in circum- 

 ftanccs in which thev could not be but of fccondary formar 

 tion. This is the fnbdaiKc of that which fccms to fiirni, 

 properly, the fixth Effay, though the author has not lo dif-r 

 tlnguiflied it. 



In the fcvcnth ElTay hp defcribes vqlcaiiic mountains as 

 Vql. VII. Z being 



