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lecond Prifm. And, by the way, what is seid of theil' Colours may be ap-plyed to their Refrangibility.

The aforesoid Wheel may be also here made uso os; and, if its Gyrarion be nei-ther too quick nor too flow, the Succession of the Colours may be disoern’d thro’the Prifm, whilst to the naked eye of a By-stander they exhibit Whitenels.

There is fömething still remaining to be seid of this Experiment. Butthis, I conceive, is enough to enforce it, and so to decide the Controvcrhe:However I shall now procced to shew some other ways of producing White-nefsby Mixtures, linee I perftvade my seif, tliat this Ast'ertion above the reitappears Paradoxical, and is with molt disticulty admitted. And becaule’ the Animadversor defires an instance of it in Bodies of divers Colours, I lhallbcgin with that. But in ordcr thereto it must be confider’d, that stich Co-loured bodies Restect but some part of the Light incident on thcm ; as isevident by the i zth I J > ojtcjhion ■. And therefore the Light Restected from an Ag-gregate of them will be much weakned by the lofs ot many Rays. V\'hencea perfect and intenso Whitenels is not tobe expected, but rather a Colour be-tween thoso of Light and Shadow, ov such a Gray or Dirty Colour as may bemade by mixing White and Black together.

And that such a Colour will resolt, may be collected from the Colour otDust found in every corner of an houso, which hath been oblerved to consistof many Colourcd particlcs. There may be also produced the like Dirty Co-lour, by mixing soveral Paintcrs Colours together. And the fäme may be ef-fected by painting a Top (such as Boys play with) ol Divers Colours. Forwhen it is made to circulate by whipping it, it will appear of soch a DirtyColour

Now, the Compounding of thesc Colours is proper to my purposo, bc-causo they dister not from Whitenels in the Species of Colour, but only ina De-gree of Luminoufnefs: Wh ich (did not the Animadversor concede it) Imight thus evince. A Beam of the Sun’s Light being tranfmitted into a dark-ned room, if you illuminate a sheet of White Paper by that Light, Restectedfrom a Bodyof any Colour, the Paper will always appear of the Colour ofthat Body, by whosc Restected Light it is illuminated. It -it be a Red Body,the Paper will be Red ; if a Green Body, it will be Grcen • and so of theother Colours. The Reason is, that the Fibres or Threads, of which the Pa-per confists, are all Transparent and Specular j and soch Substances are known .to Restect Colours without changing them. To know therefore, to whatSpecies of Colour a Grcy bclongs, place any Grey Body - (sopposo a Mixtureot Painters Colours) in the fäid Light, and the Paper being illuminated by its 1Restection fliall appear White. And the some thing will happen, if it be il-luminated by Restection from a Black Substance.

These therefore are all of one Species; but yet they scem distinguistfd not on-,ly by Degrees of Luminoufnefs, but also by some pther Inequalities, whcrebythey become more harfh or pleafänt. And the distinction fcems to be, thatGreys, and perhaps Blacks, are made by an uneven Defect of Light, confistingas it were of many little veins or streams, which dister either in Luminoufnefs, 'or in the unequal distribution of diverfly Coloured Rays ; fuchas ougly to be,VoLl. X caused