''NoW3tftwo*(?m« Objects may to eye appear of 
the fame colour, and yet one of them through a prifme feem 
and variegated with sc the edges, aod 
the oiher d^Jlin^l and entirely Gre^ii ^ or, jf there may^ be two 
Beams of Light, which falHng on a white wall do to the na- 
Hed eye exhibit the fame colour, and yet one of them, 
when tranfmitted through % Prifme^ be uniformly and r^^a. 
larly refraded^and retain its colour unchanged, and the other 
. be irregularly refraded and to divaricate into a multitude of 
othercolours jlfuppofejthefetwo^w^a/willinboth cafes be 
granted of a different Origin and conftitution. And if by 
mixing colours^ <2l green cannot be ccmpounded with thepro= 
pQYiiQS of the Vnchangeable Greeo, I think, I may call thann 
X)n'Compemded colour^ Qfpcc'M its rays are alike refran- 
giblejand uniform in all refpects. 
j The fame rule is to be obferv'd in examining, whether l{e^^ 
Orenge^ TelloTP^BleiVy or any other colour be compounded or 
not. And, by the wayjfinceall White objeds through the 
Prifine appear confus'd and terminated with colours, ^Fto^w^// 
muft, according to this diftindlionj be ever compounded, and 
that the moft of all colours, becaufe it is the moft confus'd and 
changed by Refraiflions* 
From hence I may take occafion to communicate a way for 
thelmprovement of M^Vr^/ir^^f J by Refradion. The wayij, 
by illuminating the Objed in a darkned room with Light of 
any convenient colour not too much compounded: for by that 
means the Microfcope will with diftindnefs bear a deeper 
Charge and larger Aperture, efpecially if its conftrudion be 
fuch, as I may hereafter defcribe ^ for, the advantage in Or- 
dinary Microfcopes will not be fo fenfible. 
^, . . ^ There remains now the third 
lo. That Whitenejs f6 a mixture of ^ ^ i i >i i • !_ • 
iUcohms, Qusere to be confider d, which 1$, 
Whether^^Ji^^fa^/f be an Uniform 
Colour, or a diflimilar Mixture of all colours ? The Experiraeot 
which I brought to decide it^ the Jmmadverf&r thinks may be 
otherwife explainM, and fo concludes nothing. But he fflig^t 
eafily have fatisfiedhimfelf by trying, what would be the re* 
fult of a Mixture of all colours. And that very Experiment 
might have fatisfied him, if he Iiad plealedto examine it by 
' ' ' the 
