Inquiries info Colourrd Light. Ill 



cidence at the fame time to the eve, caufe that fenfation in 

 the optic nerve. 



The (ky alfo, the lefs that clouds and reflefting vapours 

 arc mixed with it, ablorbs the light, and civcs out only this 

 blue hue, which is a refleftion deprived in part of light * : 

 the more clear the fkv, the deeper the blue: in the hiirher 

 regions of the atniofphere this blue becomes of a deep hue 

 going ofl'into dark. 



This circumftance takes place and prevails in the claro- 

 obfcuro of all figures. A true artift knows, that if he would 

 copy the real fa£i \n nature, he muft tint the going off of 

 light not with gray and black but with gradations of blues, 

 and give a faint fuifufion of green in the firft going off. 

 Zincke, the famc-us painter in enamel, underflood and copied 

 this faft : he worked an almoft infenfible green into the blues 

 of the firlt going ot!"of his lights. 



If one may then alTume the faA here grounded on the 

 experiments and obfervations of Sir Il'aac Newton, with ad- 

 dition of feme further ones on the cafe as exiting in nature, 

 that the gradations of blue are mere effefts of the privation 

 of light as it finks into ihade or darknefs ; and then, from 

 the tcftimony of the vifual fcnfes, which are the only teft in 

 the experiments above related, that the gradations of the red 

 even in the prifmatic fpace, wherein it is fuppofed to be ho- 

 mogeneous, of the orange likewife, and fo of the yellow, are 

 only gradual and luccefllve tints of the one primary ccloiir, rtif, 

 heightening, by an innumerable and infinite ferics of angles 

 of refraction, into a more and more brilliant approximation 

 of pure light, as they purify from the fufl'ufion of colour 

 which they had received in their combination with folar or 

 'terreflrial gafes and vapours; it will, on this airunijition thus 

 grounded on fafts, ftand demonftrably proved (althoueh I 

 do not venture to announce it but with every diffidence) //^^< 

 tberc are tiot feven, nor three, nor tzvo, hut only one PRI- 

 MAiiY COLOUR — a Compound bajis of all the lints of red, 

 orange, and yellow : that green, as an aitual and uncom- 

 founded primary colour, has no ex ijlence : and that the blues 

 are only hues arijing from a partial deprivation of light as 

 it goes off into darknejs. 



That all the phienomcna of colours produced by the re- 



• This circumftance, alfo. mikcs tlit ditfircnic nF the blue of tiiftiint 

 pnrtt of the landlcape as rtlic/ilcd from v.illcv.s anit Icnvet part>^, or fioin 

 the- hi;.'hcr: the- dtpriVdtion of lifiht, l>y its Ixiiii; iibl'oilicil by t!ic clL-arcr 

 air ifA tlie l:itttr c;ilc. give* a dct|)i.r blue than tli:it whicli \\, ri-Hittcd fioin 

 Ihr air hanyinj; oVir the lowci jiirtj. '1 Iiii a true aiiiA, who paints fioin 



fradlluii 



