pounding those several colours they lay on their Shels or Palads, are nothing else, but some compositum, made up of some one or more, or all of these four.
Now, whereas it may here again be objected, that neither can the Reds be made out of the Yellows, added together, or laid on in greater or less quantity, nor can the Yellows be made out of the Reds though laid never so thin; and as for the addition of White or Black, they do nothing but either whiten or darken the colours to which they are added, and not at all make them of any other kind of colour: as for instance, Vermilion, by being temper'd with White Lead, does not at all grow more Yellow, but onely there is made a whiter kind of Red. Nor does Yellow Oker, though laid never so thick, produce the colour of Vermilion, nor though it be temper'd with Black, does it at all make a Red; nay, though it be temper'd with White, it will not afford a fainter kind of Yellow, such as masticut, but onely a whiten'd Yellow; nor will the Blues be diluted or deepned after the manner I speak of, as Indico will never afford so fine a Blue as Ultramarine or Bise; nor will it, temper'd with Vermilion, ever afford a Green, though each of them be never so much temper'd with white.
To which I answer, that there is a great difference between diluting a colour and whitening of it; for diluting a colour, is to make the colour'd parts more thin, so that the ting'd light, which is made by trajecting those ting'd bodies, does not receive so deep a tincture; but whitening a colour is onely an intermixing of many clear reflections of light among the same ting'd parts; deepning also, and darkning or blacking a colour, are very different; for deepning a colour, is to make the light pass through a greater quantity of the same tinging body; and darkning or blacking a colour, is onely interposing a multitude of dark or black spots among the same ting'd parts, or placing the colour in a more faint light.
First therefore, as to the former of these operations, that is, diluting and deepning, most of the colours us'd by the Limners and Painters are incapable of, to wit, Vermilion and Red-lead, and Oker, because the ting'd parts are so exceeding small, that the most curious Grindstones we have, are not able to separate them into parts actually divided so small as the ting'd particles are; for looking on the most curiously ground Vermilion, and Oker, and Red-lead, I could perceive that even those small corpuscles of the bodies they left were compounded of many pieces, that is, they seem'd to be small pieces compounded of a multitude of lesser ting'd parts: each piece seeming almost like a piece of Red Glass, or ting'd Crystal all flaw'd; so that unless the Grindstone could actually divide them into smaller pieces then those flaw'd particles were, which compounded that ting'd mote I could see with my Microscope, it would be impossible to dilute the colour by grinding, which, because the finest we have will not reach to do in Vermilion or Oker, therefore they cannot at all, or very hardly be diluted.
Other colours indeed, whose ting'd particles are such as may be made smaller, by grinding their colour, may be diluted. Thus several of the
