Glaſs told me, that where as the Red Pigment was but Superficial, the Yellow penetrated to the very midſt of the Plate. But for further Satisfaction, not having the Opportunity to Foliate thoſe Plates, and ſo turn them into Looking-glaſſes, we Foliated a Plate of Muſcovy Glaſs, and then laying on it a little Tranſparent Varniſh of a Gold Colour, we expos'd it to the Sun-beams, ſo as to caſt them upon a Body fit to receive them, on which the Reflected Light, appearing, as we expected, Yellow, manifeſted that Rebounding from the Specular part of the Selenitis, it was Ting'd in its return with the Colour of the Tranſparent Varniſh through which it paſs'd.
EXPERIMENT XIV.
After what we have ſaid of the Compoſition of Colours, it will now be ſeaſonable to annex ſome Experiments that we made in favour of thoſe Colours, that are taught in the Schools not to be Real, but only Apparent and Phantaſtical; For we found by Tryals, that theſe Colours might be Compounded, both with True and Stable Colours, and with one another, as well as unqueſtionably Genuine and Laſting Colours, and that the Colours
reſulting from ſuch Compoſitions, would reſpectively deſerve the ſame Denominations.
For firſt, having by the Trajection of the Sun-beams through a Glaſs-priſm thrown an Iris on the Floor, I found that by placing a Blew Glaſs at a convenient diſtance betwixt the Priſm and the Iris, that part of the Iris that was before Yellow, might be made to appear Green, though not of a Graſs Green, but of one more Dilute and Yellowiſh. And it ſeems not improbable, that the narrow Greeniſh Liſt (if I may ſo call it) that is wont to be ſeen between the Yellow and Blew parts of the Iris, is made by the Confuſion of thoſe two Bordering Colours.
Next, I found, that though the want of a ſufficient Livelineſs in either of the Compounding Colours, or a light Error in the manner of making the following Tryals, was enough to render ſome of them Unſucceſsfull, yet when all neceſſary Circumſtances were duely obſerv'd, the Event was anſwerable to our Expectation and Deſire.
And (as I formerly Noted) that Red and Blew compound a Purple, ſo I could produce this laſt nam'd Colour, by caſting at ſome Diſtance from the Glaſs the Blew
part of the Priſmatical Iris (as I think it may be call'd for Diſtinction ſake) upon a Lively Red, (for elſe the Experiment ſucceeds not ſo well.) And I remember, that ſometimes when I try'd this upon a piece of Red Cloath, that part of the Iris which would have been Blew, (as I try'd by covering that part of the Cloath with a piece of White Paper) and Compounded with the Red, wherewith the Cloath was Imbued before, appear'd of a fair Purple, did, when I came to View it near at hand, look very Odly, as if there were ſome ſtrange Reflection or Refraction or both made in the Hairs of which that Cloath was compoſed.
Calling likewiſe the Priſmatical Iris upon a very Vivid Blew, I found that part of it, which would elſe have been the Yellow, appear Green. (Another ſomewhat differing Tryal, and yet fit to confirm this, you will find in the fifteenth Experiment.)
But it may ſeem ſomewhat more ſtrange, that though the Priſmatical Iris being made by the Refraction of Light through a Body that has no Colour at all, muſt according to the Doctrine of the Schools conſiſt of as purely Emphatical Colours, as may be, yet even theſe may be Compounded with one another, as well as Real Colours in