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n»nt be made in a Roctn well Darkcned, as k ought • becatrie tfaCobured Liglu is much weakened by the Reflection, and io apt to bedilutedusy the mixing os any other fcattering Light. But yet there is an Experi-ment or two farmerly mentioned, by which 1 have produced Whke out oftwoColours alone, and that variousty ; as out of Orange and a füll Blue, andout os Red and Pale Bine, and out os Yellow and Violet, as also out of o-ther pairs of intermediate Colours. The most convenient Experiment forpcrforming this, was that ot Casting the Colours os one Priim upon thofe ofanother, aster a due mannen But what N. can deduce from hence, I lee not.For the two Co'ours were Compounded of all others, and so the rcsoltingWhite, (to lj>eak properly,) was Compounded os them all, and only Decom-pounded of thole two. For Instance, the Orange was compounded of Red,Orange, Yellow, and some Green.; and the Blue, of Violet, füll Bine,light Blue, and föme Green, with ali their Intermediate Degrees; and con-lequently the Orange and Blue together made an Aggregate of all Colours taconstitute the YVhite. Thus if one mix Red, Orange, and Yellow Powdersto malte an Orange ; and Green, Blue, and Violet Colours to malte a Blue;and lastly, the two Mixtnres to malte a Grey; that Grey, though Decompound-ed of no more than two Mixturcs, is yet Compounded of all the lix Powders,as truly as if the Powders had been all mix’d at once.

This is so plain, that 1 conceive there can be no further Scruple ; elpecialiyto them who know how to examine, whether a Colour be Simple or Com-pounded, and of what Colours it is Compounded ; which having explainedin another place, I need not now repeat. If therefore N. would concludeany thiug, he must Ihew how White may be produced out of two Uncom-pounded Colours; which when he hath done, I will further teli him, why hecan conclude nothing from that. But I believe there catmot be found anExperiment of that kind ; becaufe, as I remember, I once tryed, by gradualSuccession, the Mixture of ali Pairs of Uncompounded Colours; and thoughsome oPthem were Paler, and nearer to White, than others, yet none couldbe truly call'd White. But it being some Years linee this tryal was made, 1remember not well the Circumstances, and therefore recommend it to othersto be tryed again.

sAReptyfyMe»- t. Seeing that hir. Kewton maintains his Opinion with so much concem, In ' 9? ' noC t0 ^^P ute - ® ut w * iat nieans ik, 1 pray, that he iaith, Tlxmgh I fkouid^ jleew l.dm, that tfre btfsite could bc produced of only tvpo Vnccmpoundcd Colours ,

yet 1 could Conclude nothingfrom that ? And yet hc hath athrmcd, that to com*pole the White, all Primitive Colours are Necessary.

UnfrertifyMr. 4- m y feying, that when Monsieur N. hath stiewn how VVhite may be pro-.. Newton, n.jfi. pounded out of two Unccmpounded Colours, I will teli him, wby he can Conclude nerf. öoSt. thing frmn that; my Meaningwas, That such a White, (were there any such)would have disterent properties from the White which I had respect to, whenI ddcribed my T 'heory, that is, from the White of the Sun’s immediate Light,of the ordinary Objects of our Senfes, and of all White Phaenomena that havehltherto faln under my Obfervation. And those different Properties wouldevince it to be of a different constitution: Insomuch, tiiat such » Production