Opticks 1717 - Up

224 ]
,&it ~farther , ‘t this difco&mity of pa~~f&
is the principal Caufe of the opacity of Bodies,
Will appear’by cdtYtIdering; that opake tSubitauY
c&s ‘become ;trat-Xparent by filling their Poks.
y&h any Subltmcc of e+al 0s tilmoit CquaJ deW
fit j with their parts: ‘I?ILIS T”aper dipped in
-WY ‘atey or Oil,’ the’Ckz&~s Mzdi Stone iteep’d’
ifi Water, I$uei~ Cloth oiled or varniih’~ , and:
aild ~,nlnliy other SubfEances foaked in ii~h Liquors
as will iiltintntely pClVi7dC their little
Bores, become by’ that means more t.ranfparene
than otherwife ; fo9 on the contrary, the molt
tranfparcnt Sr::bl?:nl~ces n~ay by evacuating their’
,Pores , aor fepamcing their parts, L)e rend&d
fuficientl ‘( opalse, as Salts or wet Paper, Or the
~0ctiZz~~ d zmd$Stonc ~by being dried, iF-Lorn by
being fcraped, Glafs by being reduced to POWder,
or otherwife flapred, ‘P’urpentine bv being
ftiked ‘about with Water till they ~~ix’i~n~~er~
feitly , and Water by’ being form’d into many
frnall Bubbles, either alone in the form of Froth,
or by flxllting it togethe;. with il of ‘Turpentine,
or Oil Olive, o’r uUh folne 0th conrenieiit
Liquor, with which it will not perfc&y
incorporate, Atid to’ the incrcafe of ‘the opacity
of thefeBodies it conduces fomething, that
by the z3d Obfervation the Rcflexiot~s of very
thin tranf’nrent, Subftances are colliiderably
ffronger than thofe made by the fa~nc Subltan~
ces of a @eater thickaefs, ’
PROP.