Of Simple Earths. 11 and this is one of the fureft charadters of this earth. By the experiments of Mr. Lavoifier, it ap- pears that the ftrongeft heat that can be applied, namely, that excited by pure air, is incapableof melting it. The flight degree of emollefcence that fome others have obferved, moft probably proceeds from fome flight mixture with fome other earth. Fixed alkalis, whether vegetable or mineral are the true folvents of filiceous earth in the dry way : i pa» rmneral alkali will fl ux two of fili ceous earth with effervefcence. Borax alfo fufcs hem, but much more flowly, and vvithout effer- _ Ml J cro< ; ofmic falt is ftill lefs effedhial. fixed alkahs att *ck filiceous earths alfo ,1 m ° Way ’ when VCf y min»tely divided, anc1 take up nearly 4 0 f thcir weight. bihceous fand is capable of ablorbing about £ Of US weight of water without letting tnv droj ZI, '; , bUt > 0n ex P°^e to the open* air, it anv of ‘ t /° f eVai,0rate much readily than ruÄ orego,nsearthsdoi ”“• * Of the charaüeriüng Power of the forevoinz Earths. the ^ et ^ or . tk tke di^inöive charafters of cm rk fr?'?" 1 ”’ oow to nreflino- dlfferent powers they polfefs cf im- raaers vvK COmmUniCatlllS tlieir rc,n ^hve cha- \ \ 1 m,Xe(1 or COI1 ^'iied with each «bet, to the compound of which they f ülm a 1* Gul*