C SI02 ) 
^ have defcrib'd in my Theory, the Caufes of all thefe Phd^omefia 
mull be the fame that 1 have there ailign'd. And I fee no rcafon to 
farped,^ that the fame Phenomena fliould have other caufes in the O- 
pen Air. 
The fuccefs of this Experiment may be eafily conjedurM by the ap- 
pearances of things in a Church or Chappei, whofe u indores are of 
c'olour'd glafs , or in the Open Ax, when it is illuRrated with Clouds 
of various colours. 
There are yet other ways, by v^hich I have produced Whitenefs as 
calling feveral Colours from two or more Prifmes upon the fame 
place i hy Refracting a B a n of Light with two or three Prifmes fuc- 
c,effively, to make the diverging colours converge again j hy Refle- 
ding one colour to another ; and by looking through a Prifme on an 
Objed of many colours and, ("which is equivalent to the above raen- 
tion'd way of mixing colours by concave ^(?^^^/ fillM with colourM 
liquors,) I have obferv'd the fliadows of a painted Glafs-wiodow to 
become White, where thofe of many colours have at a great diftance 
interfered. But ;yct, for further fatisfadion, the AnimAherfor may- 
try, if he pleafe, the effeds of four or five of fuch Wedges filled with 
liquors of as many feveral colours. 
Befides all thefe, the Colours of PVater-hnhbles and other thin pellu- 
cid fubftances afford feveral inftances of Whitenefs produced by 
their mixture vjithone of which I fhall conclude this particular. Let 
fome Water, in which a convenient quantity of Soap or wafli.ball is 
diffolv-'d, be agitated into Froth, and, after that froth has ftood a 
while without further agitation, tiH you fee the bubbles, of which' 
it confifts, begin to break, there will appear a great variety of colours 
all over the top of ev^ry bubble, if you view them near at hand • but ' 
if you view them at fo great a difta nee that you cannot diftinguilh the 
colours one from another,the Froth will appear perfedly White. 
Thus much concerning the defjgn 
\u T^rf/jti^eExperimentum crucis and fubftance of the Jnimadverfor's 
isfneh^ ConfidcratioHs. There are yet fome 
particulars to be taken notice of, be- 
fore I conclude ^ as the denyal of the Experimentum Cruets, . On this 
I chofc to lay the whole ftrefs of my difcourfe ; which therefore was 
the principal thing to have been objcdied againft. But 1 cannot be 
convinced ot its infufEciency by a bare denyal without affigning a 
Reafon for iu I am apt to believe, it has been mifundcrflood ; for 
' other wife it would have prevented the difcourfes about Rarifying 
and Splitting of rays h becaufe the deGgn of it is, to fliew, that Rays 
of divers colours, confider'd a part, do at Incidences fufFer 
Refraftions, without|being fplit, rarified, pr any ways dig 
kted. 
In 
