C 5102 ) 
I \nvt ddcviM-li' nif Theory, the Cauies of .^11^ t^efe p^^,,,;^^,^ 
nvyflbe the farae that 1 have there a ill gn\l. A^id Ifte ho Teafon to- 
fufpeft, that the fame Phmomena fliould have other caiifes in the Q. 
pen Air. rt • o 
The fuccefs of this Experiment may be eaiily con|eeturM by the ap'. 
pearances of things in, a Church or Chappd, whofe windores are of 
coloured glafs ^ or in the Open A.r, when it is illuftrated with Clouds, 
©f various colours. 
There are yet other ways, by which I have produced whitenefs . as 
l-ycaftin^feveral Colours from two or more Prifmes upon the fame 
place - ^filefraftingaB^anof Light with two or three Prifmes fuc- 
cvefli vely , to make the diverging colours converge again 5 by Refle- 
dincf one colour to another ; and looking through a Prifnie on an 
Objea of many colours • and, ('which is equivalent to the above men; 
lion'd way of mixing colours by concave ;r^^|-^^ fili'd with eolour*a 
liquors,) I haveobferv'dthefliadows of a painted Glafs-wifidow to 
become White, where thofe of many colours have at a great diftance 
interfered. But , yet, for further fatisfadion, the y^;?/?»p?iiz/^r/^r may 
try,if he;pleafe, theeffeftsoffour or fivcoffuch W&dges filled with 
liquors of as many feveral colours, 
^di^ts all thefe, the Colours oiPfater-iMles andothcr thin pellu* 
cid Tubilances afford feveral inftances of Whitenefs produced by 
their mixture withone of whieh I fliall conclude this particular. Let 
fomeWater,in which a convenient quantity of Soap or waflrball is 
diiiblv*d, be agkatedinto Froth, and, after that froth has flood a 
while without further agitation, till you fee the bubbles, of which 
It confifts, begin to break, there will appear a great variety of colours 
all over the top of every bubble, if you. view them near at hand ^ but, 
if you view them at fo great a diftance that you cannot diftingaifli the 
colours one from another,th« Froth will appear psrfedly White, 
Thus much concerning the defign 
li, Tljrf^ikExperimentura crucis and fubftance of the Jnimadverfor's 
^ifiick . ConfideratioBs, There are y^t fome 
partkularstobetakcnnotice of, be- 
fore! conclude ^ as the denyal of the ExfeYmentum§CrHcis. On this 
1 chofe to. lay the whole ftcefs of ray.difcourfe which therefore was 
the principal thing to have been objefted againft. But : 1 tannot be 
co.nviaccd ot itsiafufficlency by.a bare denyal without affigning a 
Eeafonfor iu 1 am apt to believe, it has been mifundcrftGod ; for 
odrerwife it would have prevented the difcourfes about Rarifying 
and Splitting of rays S becaufe the deGgn of it is, to fliew, that Rays 
#f divers colours, confider'd a part, do at £17^/4/ Incidences fuffer Vn* 
^•f ^4/ llefradions, Mithout|beirig. fplir,. r^rified^ ,or any- ways di? 
