Isaac Newton to Henry Oldenburg

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                                far from contradicting, that it would rather illustrate & confirm my Theory; because 
by y<sup>e<\sup> difference of that from other whites it would appear that other whites are not 
compounded of only two colours like that. And therefore if <s>Mr Hugens <\s> Monsr N. would 
prove any thing, it is requisite that he do not only produce out of <s>white <\s> two 
primitive colours a white w<sup>ch<\sup> to y<sup>e<\sup> naked eye shall appear like other whites, but 
also shall agree with them in all other properties.
But to let you understand wherein such a white would differ from other 
whites & why from thence it would follow that other whites are otherwise com-
pounded, I shall lay down this position 
<u>That a compounded colour can be resolved into no more simple colours 
than those of w<sup>ch<\sup> it is compounded.<\u>
This seems to be self evident, & I have also tryed it severall ways, & particularly 
by this W<sup>ch<\sup> follows. Let U+03B1 represent an oblong piece 
of white paper about 1/2 or 1/4 of an inch broad & illuminated in a dark room with a mixture 
of two colours <s>[illegible] compounded <\s> cast upon it from two Prisms,
suppose a deep blew & scarlet, w<sup>ch<\sup> <s>are<\s> must severally be as uncom-
pounded as they can conveniently be made. Then at a 
convenient distance, suppose of six or eight yards, view 
it through a clear triangular glass or crystall Prism 
held parallel to y<sup>e<\sup> paper & you shall see the two colours parted from one another colour between them.

in the fashion of two images of y<sup>e<\sup> paper as they are represented at U+03B2 & U+03B3 where suppose 
U+03B2 the scarlet & U+03B3 y<sup>e<\sup> blew, without green or any other colour between them.
Now from the afforesaid Position I deduce these two conclusions: 1 That if there were 
found out a way to compound white of two simple colours only, that white would be again 
resolvable into no more than two. 2<sup>dly<\sup> That if other whites (as that of the suns light &c)
be resolvable into more then two simple colours (as I find by experiment that they are) then
they must be compounded of more than two.
To make this plainer, suppose that A represents a white body illuminated by a direct 
beam of the sun transmitted through a small hole into a dark room, & U+03B1 such another 
body illuminated by a mixture of two simple colours w<sup>ch<\sup> if possible may make it also 
appear of a white colour exactly like A. Then at a convenient distance view these 
two whites through a Prism & A will be changed into a series of all colours, Red, Yellow 
Green Blew Purple with their intermediate degrees succeeding in order from B to C. But
U+03B1, according to the afforesaid experiment, will only yield those two colours of wch ‘twas 
compounded, & these not conterminate like y<sup>e<\sup> colours at BC but separate from one another 
as at U+03B2 & U+03B3, by means of the different refrangibility of y<sup>e<\sup> rays to w<sup>ch<\sup> they belong. And 
then by comparing these two whites, they would appear to be of a different constitution 
& A to consist of more colours than U+03B1, so that what <s>Mr Hugens<\s> Mons<sup>r<\sup> N. contends for, would 
rather advance my Theory by the access of a new kind of white then conclude 
against it. But I see no hopes of compounding such a white.
As for <s>Mr Hugens<\s> Mons<sup>r<\sup> N. his expression that I maintain my doctrine w<sup>th<\sup> some concern, I confess 
it was a little ungratefull to me to meet w<sup>th<\sup> obiections w<sup>ch<\sup> had been answered before 
without having the least reason given me why those answers were insufficient. The 
answers w<sup>ch<\sup> I speak of are in y<sup>e<\sup> Transactions from pag 5093 to pag 5102. And 
particularly in pag 5095, to show that there are other simple colours besides blew &
yellow, I instance in a simple or homogeneal green such as cannot be made by mixing 
blew & yellow or any other colours. And there also I show why, supposing that all
colours might be produced out of two, yet it would not follow that those two are the 
only originall colours. The reasons I desire you would compare with what hath 
                            
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Manuscript details

Author
Isaac Newton
Reference
EL/N1/47
Series
EL
Date
1673
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Isaac Newton to Henry Oldenburg, 1673. From The Royal Society, EL/N1/47

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