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if they be agaln Intirely mixt and blendcd together, they will again compofethat Colour, which they did besore Separation. And for the lanie reafon,.Transinutations made by the Convening of divers Colours are not real; forwhen the difform Rays are again severed, they will exhibit the very lanie Co-lours which they did besore they cnter’d the Composition; as you fee Blueand Yellow Powders, when finely mix’d, appear to the naked Eyc, Green,.and yet the Colours of the component Corpufcles are. not thereby reallyTranlmuted, but only blendcd. For when viewed with a good Microscope,.they stili appear Blue and Yellow intcrsperiediy.

y. There are therefore two sorts of Colours. The one Original and Sim-ple, the other Compounded of thefe. The Original or Primary Coloursare, Red, Yellow, Green, Blue, and a Violet-Purple, together with Orange,Indico, and an indefinite variety of Intermediäre gradations.

6. The fame Colours in Specie wiih thefe Primary ones, may be also pro-duccd by Composition. For a mixture of Yellow and Blue makes Green;of Red and Y'ellow makes Orange; of Orange and Yellowish Green makesYellow. And in general, if any two Colours be mixed, which in the Seriesof thoso generated by the Prifm are not too far distant one from ancthcr,they by their mutual Alloy Compound that Colour, which in the faid Seriesappeareth in the midway between them. But thole which are situated at toogreat a distance, do not so. Orange and Indico produce not the intermediäreGreen, nor Scarlet and Green the Intermediäre Yellow.

7. But the most lurpriling, and wonderful Composition was that of VVhite-nels. There is no one sort of Rays which alone can exhibit this. ’Tis cvcrCompounded, and to its Composition, are requisite all the aforesiid PrimaryColours, mix’d in a due Proportion. I have osten with Admiration beheld,'that all the Colours of the Prifm being made to Converge, and thereby to beagain mixed, as they were in the Light besore it was Incident upon the Prifm,reproduced Light, intirely and perfectly_White, and not at all sensibly dif-fering from a direct Light of the Sun, unieß when the Glaffes, I ufed, werenot lufficiently ciear; for then they would a little incline it to their Colour:

8. Hence therefore it- comes to paß, that Whiteneß is the ufüal Colour ofLight; for Light is a confused aggregate of Rays indued with all fort ofColours» as they are promifcuousty darted from the various parts of Lu~minous Bodies. And of such a confuled aggregate, as I faid, is generattdWhiteneis, if there -be a due Proportion of the Jngredients; but if any onepredominatc, the Light must incline to that Colour; as it happens in theBlue Flame. of Brinistone-; the Yellow Flame of a Candle; and the -various.Colours of the Fixed Stars.

9. Thefe things considered, the manner how Colours are produced-by thePrifm is evident. För, of the Rays, constitüting the incident Light, sincethose which differ in Colour proportionally differ in Refrangibility, they bytheir unequal Rcfractions muff be fevered and difperfed into an Obsong Formin an orderly fucceflion, from the least Refracted Scarlet, to the most Refra-cted Violet. And for the fame Reason it is» that Objects, when looked. uponthro’ a Prifo, appear Coloiured.-, For the Difform Rays, by- their -unequal

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