B. By Means of the different Degrees of its Refrangibility; for those Rays which are leaft refrangible, are tinctured with Red, and paint that Colour on Bodies; and those which are moft refrangible, are violet Purple, and paint Bodies therewith; and the intermediate Degrees of refrangible Rays, are dyed with the intermediate Colours, in the Order as before-mentioned.

A. By what Experiment do you prove this Doctrine ?

B. By this eafy one following: In a Chamber made dark, make an oblong Hole in the Window-Shutter at F, about of an Inch in Breadth; through which will enter the Sun Beam FH, and a large Prism ABC, placed at about 20 Feet from the Hole, will refract the Rays of this Beam; after which they will again unite and become a white Beam at H, where let be applied an opake Body GHI, at the Distance of z or 3 Feet from the Prifm, in which let there be an oblong Hole made at H, or of an Inch in Breadth, through which the white Part of the Beam being tranfmitted, and made to fall on a Piece of white Paper placed after, will there paint the primitive original Colours of Light; fuppofe Red at t, Yellow at s, Green at r, Blue at q, and Violet at P. See Fig. XII.

A. Well, very good, and what is the Confequence of all this, Sir? B. Why

Of the Nature and Order of Colours. 63

B. Why then with a Piece of Wire R (or any opake Thing about of an Inch thick) you may, by intercepting the Rays at k, l, m, n, o, take away any one of the Colours at t, s, r, q, or P, whilft the other Colours remain as before.

A. What do we learn by this Experiment ?

B. First, That the Rays of Light paint natural Bodies with different Colours: Secondly, That the leaft refrangible Rays, as t, paint Red; and the moft refrangible ones, as P, paint the deepeft Violet Purple; and that other intermediate refrangible Rays paint the other intermediate Colours: Thirdly, That thofe Differences of Colour are abfolutely and really exifting in the Rays of Light, and do not arife from the different Confines of Shadow, variously modifying the Light, as has hitherto been the Opinions of Philofophers.

A. I think it feems from hence, as if you would infinuate, that Colours are not connate with Bodies, or naturally in them, but painted on them by the Rays of Light.

B. 'Tis very true: Colours only are in the Rays of Light, not in Bodies; and all Bodies are of the fame Hue in the Dark, and appear differently colour'd only by, and in the Light.

A. Strange Doctrine this! I am apt to think you'll perfwade very few that Colours

are

are not in Bodies, when they constantly fee all around them tinged with fuch an agreeable Variety.

B. If they will not be convinced by Reafon and Experience, they must remain Ignorant, and still poffefs their Prejudices and Errors.

A. But according to this Notion of Cotours, how comes it to pafs that fome Bodies are all of one Colour, fome all of another, and fome of fo many different Colours?

B. This is eafily conceived; for the Matter of fome Bodies univerfaliy reflect one Sort of Rays more copioufly than another; and according to the Refrangibility of those Rays are the Bodies colour'd: Thus Minium reflects the leaft refrangible Rays most copioufly, and thence appears Red; Violets reflect the most refrangible Rays, and thence have their Colour; and fo of their intermediate Degrees: Again, the Matter of fome. Bodies is fuch as reflects different refrangible Rays; and therefore is in various Parts of various Colours.

A. Pray, Sir, what can be the Meaning that White and Black are not reckon'd among the primary Colours of Light?

B. Becaufe White is fo far from being a pure, fimple, original Colour, that, on the contrary, 'tis a Mixture of all thofe 7 original Colours together; or a Compofition of

Colours,

Of the mufical Harmony of Colours. 65 Colours, even all the Colours in Nature: And on the other Hand, Black is properly no Colour at all, being only the Hue of those Bodies, whofe Subftance abforbeth all the Rays of Light, and therefore by reflecting none, cannot, of Confequence, be colour'd at all.

A. Then thofe Bodies which appear White, I apprehend, are fo by reflecting promifcuously all the Rays of Light which fall on them.

B. Yes, they are fo. I have one Thing more very curious on this Head of Colours to relate to you, and then, if you please, we, will make a Tranfition to another Subject.

A. Pray what is that? I long to know, being ravished with thefe Kinds of natural Curiofities.

B. It is this: Sir Ifaac Newton, by Experiments, hath found that the Colours of Light, with refpect to their Quantity, were in Proportion to the feven musical Notes, or Intervals of Sound, contained in an Octave, viz. Sol, la, fa, Sol, la, mi, fa, Sol. See Fig. XIII.

A. Blefs my Stars! a Discovery indeed! fure the happiest Man alive for Experiment! What! Mufic and Harmony in Colours!

B. Yes, he discovered it thus: He caufed a Sun Beam to be largely refracted on the F

Side

Side of a dark Chamber, which produced the Spectrum of Colours, reprefented by ABCDEF; in which he caufed an Affiftant exactly to mark the Confines of each Colour, by drawing parallel Lines betwixt each, as am, bi, ck, &c. and thus the Spaces V, I, B, G, Y, O, R, reprefents the Quantity of the refpective Colours, viz. Violet, Indigo, Blue, Green, Yellow, Orange, and Red: And upon a nice Examination, he found the parallel Sides of the Spectrum AF and CD, to be divided in the Points a, b, c, d, &c. juft in the Proportion as a mufical Chord is divided for the Concords of an Octave, viz. as the Intervals of thefe Numbers, 1. . . 4.3.3. 16. 4.

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A. This would induce one to think there were fome Kind of Relation between Mufic and Colours; fince it hence appears, that in Nature, they are adjusted in the fame. Proportion, and both defigned to delight and please Mankind, and footh the Cares of Life.

B. One Thing more I must remind you of, and that is this: Some Perfons tell us Colours are tangible Qualities, and may be distinguished by Feeling, and give an Inftance of one that could and did do it: But this is certainly impoffible to do naturally; and therefore if any one ever did do it, he must have a miraculous Gift of Feeling.

CHAP.