1000000031

on.

",,1,,",

ll~ ;o~"'

",..rt

<>f

l'ht.

,'¡h..,

Tmg

fOlDe

otber colour "ppearcd

Wh~D 1h~

plate

WJS

vicwed

d irctUy ;

th~t

is, Goce hit

tbi.

dilatation o,f

the

rings

th:u rhe ft f eral parts of (be

ates

change thetr colours ;

it follows, tb...oy part of a

plll.te

of water eneomparred

witb air eb':Iges eolour lefs upon being viewed obliquely,

tilan a.y

Fut

pla!e of air eneomparred witb glaf•.

11Th", Ihe mediu", 'Which encoml'affa a colollred Iran!–

p;uenl I"ale jI ¡:iven, Ihe eo{our¡ change lefl ul"

on alurillg the

jituali"...,

the ej e,

the

¡ .,/J .

jlan«

more d,,¡fe

0"1

of 'Whic¡' Ihal piafe

j¡

made.

The m.tter out of whieh a bubble of wate r i. made

not fo denfe as that out of whieh a bubble of glafs i.

nude, and glaf. i. not fo denfe as the feoria or glarry

fkin thro wn out by metals wheo tbey are heated .

Now,

any of thefe. pl'H' enber of water, or

gl.fs

, or metal–

I,ne fubfi anee, wben ,hey He eoeomp.rred w,ith lhe fame

r.l!diunl air, wlll change thetr .cplour a

liule

upon being

vie'._ed obliquely; but the plate Qf W2fer ehange. the

mofi, the p,late of glaf. lef. than that, aod the fe9rio of

met.1s leafi of all .

Oflh.

O¡.AItEN .... TRANSPARBNCY, andCO'LOURS

NATURAL Boo, .s.

7h.

opa~<n'fl

of hodia

j¡

. wing fo fhe man) r'.fit Rionr

and refranionr 'Whil:h Ihe rap of lighf f •.Ifer 'Wilhin

hofe bQdia.

fmallen

por..

of almofi all

oatur~1

bodie. are traof–

pareot, as

",i11

re.day be grant.d by thofe wbo have

been ufed tO look through microfeope,_ A pieeeor leaf.

gold i. tranfparent if it i. hcld up ag.infi the hole of

wiodow.{huner

a dark room;

and any

other

fubfiance.

however opake it m.y

f~em

io the open air, will appear

tranfp.rent by the

f.me

meon., when it 'i. made of a.fuf–

-licient thionef.. Even metal. beeome tranfp.rent, if

they are dirrolved in a proper meollruum, a. gold in aqua

~egi.,

or filver in oqua forti. ; and by being thu. di/folved,

are redueed to very fniall particle. . But finee even io o·

pake bodies every Gngte particle

tranfmit~

tight, or i, tranf–

parent, the whole would like\Vife traofmit light, uolef,

the ray', wheo they are to p.f. through all the particlos

which male up ,he whole, were fo turoed oUt of the way

b y innumerable refraaioos and reOeaion" as to be Ilop .

ped and fupprerred in their parrage. That this i. the rea–

fon why bodie. tha! eonfill of tranfparent partiel•• (hould

opake. i. evident; finte opakc;. bodie" when they are

re:duced

a fuffi cient thinnefs, become tranfparent : for

thea there will be but fe w partiel.. Iying beyood one a–

Do>her for lhe light to pafs through; and., lhe rays will

fufter fewer refraaion. and rofleaion., foone of them may

i:et through a thin plate, .hough

. 11

th~m

would be

fupprell'ed in a thieker maf. of the fame fubn.n ee.

The m.dium. 'Wifh which fhe pora of p,;aAe hodiu

Are

jilltd.

nof of Ihe fA"" d.n.fil) 'Wifh fhe 'A rficlu

hof. ¡odiu.

Boo,

E S

eonfifi of tranfparent particle., and their

'Pakenefs i•.owing to the.

m~ny

ren.aions

an~ refra~ion,

...hieh the Ioght fuften wllh,n them . Now,'¡ the 'nter–

fliee. betweeo tbe partiele. of any body \Vere 611ed witb

rne¿¡¡~m

uf .he fame deofity

"ith ,he

plrtÍd

es,

,1,e lie",

w?"td neither

refraéled oor re1leéled as it paH'ed

01 the particks 1.0[0 tbe lntedlices and

OUt

of lhe inter ..

niees jotO me pares, bUl

wouLd

par,

lbrough the

body.

and the body would be traafpareot. ConfequentJy, iDao

opake body, wbere the tight is fupprell'ed by tbe refrac .

tiaos and reBeétioos which it

fu ffers,

rhe particJes

!hit

compofe the body. 2nd the medium tbat lill. the poreo

or interfiie"s between tite particle., tDufi be of diff<rent

denlitie~

H enee we may fre the reafon why

~aper,

wheo it hu

ueeo

dipped

in water or oil, is more tnnCparent thao

when it is dry . For when ,the paper i. tboroughly \Vet–

ted with water or oil, the pores of it are filled with o

medium that i. oeorl,. of the fame denfity with i.. par–

ticles .

,be eontrary, though oil of rurpentioe anei

water are both of them traOfparenl when they are fepa–

rOl

;

yet if they are fhaken together fo as to mil{ but;na.

perfeétly, the mixture becomes much lefa tranfparenc ..

beeaufe the par" of

e~" h

fluid are feparated from one

nOlher, aod thoCe of the other Ouid, "hieh are of a di!.

ferent denGty, get in between them_

r he par f,

hodier, and Ihtir inferjlien, mujl nof •• ¡eJi

Ihan

A cerfain definif. Hgn<fl fo render Ihe", opai'.

and colouru/.

mofi opake bodie. become traofpareD! when their

partiele. are fubtilly di.ided ;

mefals, fueh 2' gold or

lilver, whieh are opake in luge marres, beeome tranfpa.

rent wheD tbe former is dilfolved

aqua regia, aod the

latter in aqua foni.. Aod we obferved, that at lbe top

of a

bubble of water, where t):¡e water

eXlremely thin,

there is a blaek

CpOt,

whieh reflea. fearee any light ot

all; though the water is iencompaíTed with air, whicb is

medium of • difterent deoGty_ CooCequently, if the dia–

meter of the paniele. of whieh .ny natural fubllaAte

confifis was no greater than Ihe thicknefs of the bubblo,

where it refieas no light, but tronfmi.. aJl. fueh a body

would be tranfparent. notwithOanding

tbe

¡oterllice.

tha! are between in particl.. \Vere filled with a medium

tbe denGty of whieh i. different from theirs.

like manner, we obferved, ,hat when a thin plate

air Iies between two pieee. of

gl.fs

BAC,DAE. (No

40.)

there is a dark fpot, which reneas no light, and tranfmita

aJl, not only at the point A where the gtarres toueh one

aoother, but

~Ifo

round' that poin. tO fome difiaoee where

the glaffes are very oear to one anotber. From hence

may eonelude, lha! though the particle. of any natural

fubfianee' were a. denfe as glafs, and the medium whieh

Glls

their ioterfiices was as.rare as air; yet if thefe ¡oter..

fiices were

bigger than the ¡nterval between the two

glarre. BAC, DAE, at that place whe.. alllight is tnof.

milled, fueh a body would be tranCparen!.

The tranfpareney of water feem. to be owing to the

ca.ufe.

here

mentioned, to the fmallnefs of in parts, or

i..

pore., or of both . For we are fure that the pores

of water are filled with air, bee.ufe tbe air may be dfiwn

out (rom the water in an air.pump; and confequently,

a. the pore. are

~lIed

with a medium of a different den ·

lity from the parts, the mixture ought to be opake, like

(uch a mixture of water and oil of turpentine as was

mentioned

abov~'

Btu the fmallnefs eitber of tbe

p.m,