If you take Blue _Smalt_, you shall find, that to afford the deepest Blue, which _cæteris paribus_ has the greatest particles or sands; and if you further divide, or grind those particles on a Grindstone, or _porphyry_ stone, you may by _comminuting_ the sands of it, _dilute_ the Blue into as pale a one as you please, which you cannot do by laying the colour thin; for wheresoever any single particle is, it exhibits as deep a Blue as the whole mass. Now, there are other Blues, which though never so much ground, will not be _diluted_ by grinding, because consisting of very small particles, very deeply ting’d, they cannot by grinding be actually separated into smaller particles then the operation of the fire, or some other dissolving _menstruum_, reduc’d them to already. Thus all kind of _Metalline_ colours, whether _precipitated_, _sublim’d_, _calcin’d_, or otherwise prepar’d, are hardly chang’d by grinding, as _ultra marine_ is not more _diluted_; nor is _Vermilion_ or _Red-lead_ made of a more faint colour by grinding; for the smallest particles of these which I have view’d with my greatest Magnifying-Glass, if they be well enlightned, appear very deeply ting’d with their peculiar colours; nor, though I have magnified and enlightned the particles exceedingly, could I in many of them, perceive them to be transparent, or to be whole particles, but the smallest specks that I could find among well ground _Vermilion_ and _Red-lead_, seem’d to be a Red mass, compounded of a multitude of less and less motes, which sticking together, compos’d a bulk, not one thousand thousandth part of the smallest visible sand or mote. And this I find generally in most _Metalline_ colours, that though they consist of parts so exceedingly small, yet are they very deeply ting’d, they being so ponderous, and having such a multitude of terrestrial particles throng’d into a little room; so that ’tis difficult to find any particle transparent or resembling a pretious stone, though not impossible; for I have observ’d divers such shining and resplendent colours intermixt with the particles of _Cinnaber_, both natural and artificial, before it hath been ground and broken or flaw’d into _Vermilion_: As I have also in _Orpiment_, _Red-lead_, and _Bise_, which makes me suppose, that those _metalline_ colours are by grinding, not onely broken and separated actually into smaller pieces, but that they are also flaw’d and brused, whence they, for the most part, become _opacous_, like flaw’d Crystal or Glass, &c. But for _Smalts_ and _verditures_, I have been able with a _Microscope_ to perceive their particles very many of them transparent.