( ^096 ) 
in foluth frincipiifjor of a texture penetrable by mineral famc$5 
iBfthly, trom the Heterogeneous matter included in Solid » 
Gerosjboth tranfparcnt, andopacous, though very rarely in 
the foripcr kind 5 fixthly,from the proofs^to be met with hi- 
low in the fecond member of the Authors Hypothcfisjwhereio 
it appear$,that feveral even of the Tranfparent Gems have mc« 
taUine or other extraneous mineral bodies mingled with them 
per mimma-jVi/hich mixture is reafonably fuppofed to have been 
made, when the mingled bodies were in a fluid form- 
Thefeconfiderations being difparch't^they arc follow*d with 
a very Inftrudivc Anfwer to a main Objeftion,raifed from the 
cxquifite uniformity of fliape,fo admired in GemS) (efpccially 
the Prifmatical one in Cryftal J and thought to demooftrate 
their being formed by a Seminal and Geometrizing Principle. 
This done^the Author proceeds to the fecondot thofe Grand 
Arguments^whereon his Hypotheiis was grounded* And this is 
built upon the wii^bt of (ome Gems, which being greater than 
that which feems to belong to them as bard and tranfparent 
Stones, . he thinks he may probably derive it from Metallin or 
Mineral mixtures. Where he (hews, how he came to know the 
traih of what he here delivers, and what ftandard he pitches 
upon whereby to make a probable cflimate of the weight of 
Gems ; which was by finding out the Ponderoufnefs of Cry* 
fiai in reference to Water. 
To this He fiibjoyni a third Arg«ment,tak<eo from hence, that 
out of divers Medicinal Stones, and even out of fome fine 
Gems,rearand corporeal Metals or other Mineral fnbftances 
snay be cxtraded : which Argument he profecutes largefy in 
the SnondSeSion i where he delivers 
A Gon}e<!lure about the Caufu of the Vittuesof Gemsjwhich 
h^Tbat the Author conceives, thatfome{'at leaft^of the re^l 
Virtues (the many fabulous ones being by him juftiy exploded;) 
of divers Gems may be derived from this$ That whilft they 
were in a fluid form for at teaft not yet hardoed^) the Petref* 
cent fubftance was mingled with fome Mineral fbfution or 
tindure, or with fome other impregnated liquor, and that 
thcfe were afterwards coR.coagdated,or united and hardned 
into one Gcm.And as divers of the Virtues of Gems may be in 
