and comparing with some of the Entire Crystalls purposely reserv'd, some of the Subtile Powder of the same Salt, which will Comparatively exhibit a very considerable degree of Whitishness.
13. Seventhly, And as by a Change of Position in the Parts, a Body that is not White, may be made White, so by a Slight change of the Texture of its Surface, a White Body may be Depriv'd of its Whiteness. For if, (as I have try'd in Gold-smiths Shops) you take a piece of Silver that has been freshly Boyl'd, as the Artificers call it, (which is done by, first Brushing, and then Decocting it with Salt and Tartar, and perhaps some other Ingredients) you shall find it to be of a Lovely White. But if you take a piece of Smooth Steel, and therewith Burnish a part of it, which may be presently done, you shall find that Part will Lose its Whiteness, and turn a Speculum, looking almost every where Dark, as other Looking-glasses do, which may not a little confirm our Doctrine. For by this we may guess, what it is chiefly that made the Body White before, by considering that all that was done to deprive it of that Whiteness, was only to Depress the Little Protuberances that were before on the Surface of the Silver
into one Continu'd Superficies, and thereby effect this, that now the Image of the Lucid Body, and consequently a Kind of Whiteness shall appear to your Eye, but in some place of the greater Silver Looking-glass (whence the Beams reflected at an Angle Equal to that wherewith they fall on it, may reach your Eye) whilst the Asperity remain'd Undestroy'd, the Light falling on innumerable Little Specula Obverted some one way, and some another, did from all Sensibly Distinguishable parts of the Superficies reflect confus'd Beams or Representations of Light to the Beholders Eye, from whence soever he chance to Look upon it. And among the Experiments annex'd to this Discourse, you will find One, wherein by the Change of Texture in Bodies, Whiteness is in a Trice both Generated and Destroy'd.
CHAP. II.
1. What we have Discours'd of Whiteness, may somewhat Assist us to form a Notion of Blackness, those two Qualities being Contrary enough to Illustrate each other. Yet among the Antient Philosophers I find less Assistance
to form a Notion of Blackness than of Whiteness, only Democritus in the passage above Recited out of Aristotle has given a General Hint of the Cause of this Colour, by referring the Blackness of Bodies to their Asperity. But this I call but a General Hint, because those Bodies that are Green, and Purple, and Blew, seem to be so as well as Black ones, upon the Account of their Superficial Asperity. But among the Moderns, the formerly mention'd Gassendus, perhaps invited by this Hint of Democritus, has Incidentally in another Epistle given us, though a very Short, yet a somewhat Clearer account of the Nature of Blackness in these words: Existimare par est corpora suâpte Naturâ nigra constare ex particulis, quarum Superficieculæ scabræ sint, nec facilè lucem extrorsum reflectant. I wish this Ingenious Man had enlarg'd himself upon this Subject; For indeed it seems, that as that which makes a Body White, is chiefly such a Disposition of its Parts, that it Reflects (I mean without much Interruption) more of the Light that falls on it, than Bodies of any other Colour do, so that which makes a Body Black is principally a Peculiar kind of Texture, chiefly of its Superficial Particle, whereby it does as it were Dead the Light
that falls on it, so that very little is Reflected Outwards to the Eye.
2. And this Texture may be Explicated two, and perhaps more than two several ways, whereof the first is by Supposing in the Superficies of the Black Body a Particular kind of Asperity, whereby the Superficial Particles reflect but Few of the Incident Beams Outwards, and the rest Inwards towards the Body it self. As if for Instance, we should conceive the Surface of a Black Body to be Asperated by an almost Numberless throng of Little Cylinders, Pyramids, Cones, and other such Corpuscles, which by their being Thick Set and Erected, reflect the Beams of Light from one to another Inwards, and send them too and fro so often, that at length they are Lost before they can come to Rebound out again to the Eye. And this is the first of the two mention'd ways of Explicating Blackness. The other way is by Supposing the Texture of Black Bodies to be such, that either by their Yielding to the Beams of Light, or upon some other Account, they do as it were Dead the Beams of Light, and keep them from being Reflected in any Plenty, or with any Considerable Vigour of Motion, Outwards. According to this Notion it may be said, that
the Corpuscles that make up the Beams of Light, whether they be Solary Effluviums, or Minute Particles of some Ætherial Substance, Thrusting on one another from the Lucid Body, do, falling on Black Bodies, meet with such a Texture, that such Bodies receive Into themselves, and Retain almost all the Motion communicated to them by the Corpuscles that make up the Beams of Light, and consequently Reflect but Few of them, or those but Languidly, towards the Eye, it happening here almost in like manner as to a ball, which thrown against a Stone or Floor, would Rebound a great way Upwards, but Rebounds very Little or not at all, when it is thrown against Water, or Mud, or a Loose Net, because the Parts yield, and receive into themselves the Motion, on whose Account the Ball should be Reflected Outwards. But this Last way of Explicating Blackness, I shall content my Self to have Propos'd, without either Adopting it, or absolutely Rejecting it. For the Hardness of Touchstones, Black Marble and other Bodies, that being Black are Solid, seem to make it somewhat Improbable, that such Bodies should be of so Yielding a Texture, unless we should say, that some Bodies may be more Dispos'd to Yield to the Impulses of