( '§7 )

s. Thenext Experimenti made in uncompoundedColours (asMr. Kewtonterms them, Pros. s. L- i;.) as follows. Having cast two Coloured Imagesupon the Wall, so as the Scarlet Colour of the one did fall in a Streight;

Linc (Parallel to the Horizon) with the Violet of the other : I then lookedupon both through another Prisin, and found them still appear in a StrcightLine Parallel to the Horizon, as they had formerly done to the Naked Eye.

Now According to Mr. Newtons Assertion of Difterent Refrangibility in Dif-ferent Rays, I conceive the Violet Rays fhould liifter a greater Refractionin the Prilhi at the Eye, thun the Scarlet ones; and confequently both Co-lon rs fhould not appear in a Streight Line Parallel to the Horizon.

6 . Another Experiment I made, in order to forne further Dilcovery of thatlürprizing Phaenomenon of the Coloured Image, which occafioned Air. Nor-tons Ingenious Theory of Light and Colonrs, as also his excellent invcntion ofthe ReHecting Tclefcope and A lictos cope. Having then somctimes luspectcdthat not only the Dircct Sun-Beams, butalso other Extraneous Light, mightpollibly influence the Coloured SpcBrum, I hoped to difcovcr the Truth ofthis suspicion by means of the Sun-fpots, made to appear in the ColouredImage, by placing a Telefcope behind the Prisin. But my Endeavours pro-ving Ineffectual herein, by Reason of some Intervening difhculties, I thoughcat Lcngth of a more feafiblc Mcthod in order to the dcsigned Dilcovery, asin the following Experiment.

I fastned a very White Paper-Circle (about an Inch in Diameter) upon my ?,>. 77, -Window-fhuts; and beholding it thro’ my Pristn, I found a Coloured ImagePainted thercby upon my Retina, anfwerable in almost all rcfpects to the for-mer of the Sun-beams upon the Wall, elpecially when the Paper-Cirde was in-differently well illuminated. This Image indced- appearcd contrary to theformer, as to the Situation of Colours, that is, the Scarlet appearing a bove,the Violet below, tho’ but faint. But this I was not surprilcd at, having ob-lerv’d upon dissecting the Eye, that Objects are Painted on the Retina astera contrary Posture to what they appear to fight. Having.thus rendered theColoured Image much more tractable than formerly it was, I conceived goodhopes of some further Dilcovery in the point mentioned.

I11 purfuance then of my former suipicion, having fixed my Prisin in asteady Posture, I caused the Paper C, to be applied dole 11 p the Paper-Circle/ib d: whereupon the former Violet d, and the Scarlet Colour of C, vanishedinto Whitenefs. Next I removed the mentioned Circle from the Shuts, and ■placed it in the open Window, supportcd only by the edge d : whereupon, tomy astonifhment, ali the former Colours exchanged Posturcs in the Retina,the Scarlet now appearing below, the Violet above ; the Intermcdiate Co-lours fcarce dilcernable. And here, on the by, sttsvcry Rcmarkable, that du-ring this Obfervation, I xlearly perceived both Bluc and Scarlet Light to beTransparent, I bemg able to dileern leveral Objects thro' both, namely Stee-ples opposite so my Window. Whence it follows, that thele Colours do ingreat part arife from the Neighbouring Light. Lustly, I placed the Paper-Circle anew, so as the one half b, was fastned to the Ihuts, the other Se-rrae ircle a, being exposed to the open Air. Whereupon the Semicircle it, be-

came