of colours in solid bodies, in such lines and figures, as they may over-power the natural or artificial inherent colours in solid bodies, and for a time make other colours, and many times the lines of light or of shadows will meet and sympathize so with inherent colours, and place their lines so exactly, as they will make those inherent colours more splendorous then in their own nature they are, so that light and shadows will add or diminish or alter colours very much. Likewise some sorts of colours will be altered to our sight, not by all, but onely by some sorts of light, as for example, blew will seem green, and green blew by candle light, when as other colours will never appear changed, but shew constantly as they are; the reason is, because the lines of candle light fall in such figures upon the inherent colours, and so make them appear according to their own figures; Wherefore it is onely the alteration of the exterior figures of light and shadows, that make colours appear otherwise, and not a change of their own natures; And hence we may rationally conclude, that several lights and shadows by their spreading and dilating lines may alter the face or out-side of colours, but not suddenly change them, unless the power of heat, and continuance of time, or any other cause, do help and assist them in that work of metamorphosing or transforming of colours; but if the lines of light be onely, as the phrase is, Skin-deep; that is, but lightly spreading and not deeply penetrating, they may soon wear out or be rubbed off; for though they hurt, yet they do not kill the natural colour, but the colour may recover and reassume its former vigour and lustre: but time and other accidental causes will not onely alter, but destroy particular colours as well as other creatures, although not all after the same manner, for some will last longer then others. And thus, _Madam_, there are three sorts of Colours, Natural, Artificial, and Accidental; but I have discoursed of this subject more at large in my Philosophical Opinions, to which I refer you, and rest, Madam, _Your faithful Friend_ _and Servant._ XLI. _MADAM,_