f 4096 ) 
infohiU ^rimipiif^ ^m%tuto pencttabJe by mineral fbmesj 
iithly, trom the Heterogeneous matter iddudcd in Solid 
Gemsjboth tranfparcut, and opacous, though very rarely in 
the former kind v ^^xtWysfrom the proofs^to be met with be- 
low in the fecond member of the Authors Hypothefis^whereia 
it appearsjthat feveral even of the Tranfparent Gems have me-^ 
taUineor other extraneous mineral bodies mingled with them 
^frwi/«>w^; which mixture isreafonably fuppofed to have been 
made^when the mingled badies were in a jSuid form* 
ThefeconfideratioQS being difpatch't^they are follow'd with 
a very Inftrudive Anfwer to a main ObjeitioPjraifed from the 
cxquifice uniformity of fliape/o admired in Gems, (efpccially 
the Prifmatical one in Cryftal,^ and thought to demonftratc 
their being formed by a Seminal and Gcometrizing Principle, 
This donCjthe Author proceeds to the /econd of thofe Grand 
J^crgumentSjwhereon his Hypothefis was groundcd^And this is 
built upon the rveight of fome Gems^ which being greater than 
that which feems to belong to them as hani and tranfparenc 
Stones, he thinks he may probably derive it from Metallin or 
-Mioeral mixture he fliew5,how he came to know tht 
truth of what he here delivers, and what ftandard he pitch'c 
tipon whereby to make a probable eftimate af the weight of 
Gems; which was by finding out the Pondcroulbefs of Cry. 
%1 in reference to Wat 
To this he fubjoyn* a third Argument^taken from hence, that 
®uc of divers Medicinal Stones^ and even out of fome fine 
Cems^real andicorporeal Metals or other Mineral fobflanccs 
may be cxtrac9:ed : which Argumeniheprofecutes largely in 
the Second S eShn - where he delivers ' 
AGonjeAure about the €aufeso£ thtVirtuesof Gemsjwhicli 
tf ^Thal the Author conceives, that fome fat Icaft ; of the reii^ 
Virtues (the many fattdoui ones being by him jufily exploded) 
of divers Gem* may be derived from this That whilft they 
.^ere in a fluidform^(or at feaft not yet hardned,) the Petref. 
cent fiibflante was mingled with feme Mineral iblution^r 
tindiure,: or. with fome other hnpregnated liquori an^that 
thefe^ere ^er wards cos-coagulatedyor aoi ted ?a«d hardned 
^nlOvOfl^iGemg^ed^ar^ of Gemrmay be ia^ 
