The whiteness also of froth, is for the most part to be ascribed to the reflection of the light from the surface of the air within the Bubbles, and very little to the reflection from the surface of the Water it self: for this last reflection does not return a quarter so many Rays, as that which is made from the surface of the air, as I have certainly found by a multitude of Observations and Experiments.

The whiteness of Linnen, Paper, Silk, &c. proceeds much from the same reason, as the Microscope will easily discover; for the Paper is made up of an abundance of pellucid bodies, which afford a very plentifull reflection from within, that is, from the concave surface of the air contiguous to its component particles; wherefore by the affusion of Water, Oyl, Tallow, Turpentine, &c. all those reflections are made more faint, and the beams of light are suffer’d to traject & run through the Paper more freely.

Hence further we may learn the reason of the whiteness of many bodies, and by what means they may be in part made pellucid: As white Marble for instance, for this body is composed of a pellucid body exceedingly flaw’d, that is, there are abundance of thin, and very fine cracks or chinks amongst the multitude of particles of the body, that contain in them small parcels of air, which do so re-percuss and drive back the penetrating beams, that they cannot enter very deep within that body; which the Microscope does plainly inform us to be made up of a Congeries of pellucid particles. And I further found it somewhat more evidently by some attempts I made towards the making transparent Marble, for by heating the Stone a little, and soaking it in Oyl, Turpentine, Oyl of Turpentine, &c., I found that I was able to see much deeper into the body of Marble than before; and one trial, which was not with an unctuous substance, succeeded better than the rest, of which, when I have a better opportunity, I shall make further trial.

This also gives us a probable reason of the so much admired Phænomena, of the Oculus Mundi, an Oval stone, which commonly looks like white Alabaster, but being laid a certain time in Water, it grows pellucid, and transparent, and being suffer’d to lie again dry, it by degrees loses that transparency, and becomes white as before. For the Stone being of a hollow spongie nature, has in the first and last of these appearances, all those pores fill’d with the obtunding and reflecting air; whereas in the second, all those pores are fill’d with a medium that has much the same refraction with the particles of the Stone, and therefore those two being contiguous, make, as ’twere, one continued medium, of which more is said in the 15. Observation.

There are a multitude of other Phænomena, that are produc’d from this same Principle, which as it has not been taken notice of by any yet that I know, so I think, upon more diligent observation, will it not be found the least considerable. But I have here onely time to hint Hypotheses, and not to prosecute them so fully as I could wish; many of them having a vast extent in the production of a multitude of Phænomena, which have been by others, either not attempted to be explain’d, or else attributed to some other cause than what I have assign’d, and perhaps than the right; and therefore I shall leave this to the prosecution of such as have more leisure: onely before I leave it, I must not pretermit to hint, that by this Principle, multitudes of the Phænomena of the air, as about Mists, Clouds, Meteors, Haloes, &c. are most plainly and (perhaps) truly explicable; multitudes also of the Phænomena in colour’d bodies, as liquors, &c. are deducible from it.

And from this I shall proceed to a second considerable Phænomenon which these Diamants exhibit, and that is the regularity of their Figure, which is a propriety not less general than the former, It comprising within its extent, all kinds of Metals, all kinds of Minerals, most Precious stones, all kinds of Salts, multitudes of Earths, and almost all kinds of fluid bodies. And this is another propiety, which, though a little superficially taken notice of by some, has not, that I know, been so much as attempted to be explicated by any.

This propriety of bodies, as I think it the most worthy, and next in order to be consider’d after the contemplation of the Globular Figure, so have I long had a desire as wel as a determination to have prosecuted it if I had had an opportunity, having long since propos’d to my self the method of my enquiry therein, it containing all the allurements that I think any enquiry is capable of: For, first I take it to proceed from the most simple principle that any kind of form can come from, next the Globular, which was therefore the first I set upon, and what I have therein perform’d, I leave the Judicious Reader to determine. For as that form proceeded from a propiety of fluid bodies, which I have call’d Congruity, or Incongruity; so I think, had I time and opportunity, I could make probable, that all these regular Figures that are so conspicuously various and curious, and do so adorn and beautifie such multitudes of bodies, as I have above hinted, arise onely from three or four several positions or postures of Globular particles, and those the most plain, obvious, and necessary conjunctions of such figur’d particles that are possible, so that supposing such and such plain and obvious causes concurring the coagulating particles must necessarily compose a body of such a determinate regular Figure, and no other, and this with as much necessity and obviousness as a fluid body encompast with a Heterogeneous fluid must be protruded into a Spherule or Globe. And this I have ad oculum demonstrated with a company of bullets, and some few other very simple bodies; so that there was not any regular Figure, which I have hitherto met withall, of any of those bodies that I have above named, that I could not with the composition of bullets or globules, and one or two other bodies, imitate, even almost by shaking them together. And thus for instance may we find that the Globular bullets will of themselves, if put on an inclining plain, so that they may run together, naturally run into a triangular order, composing all the variety of figures that can be imagin’d to be made out of æquilateral triangles; and such will you find, upon trial, all the Surfaces of Alum to be compos’d of: For three bullets lying on a plain, as close to one another as they can compose an [Schem. 7.]
Fig. A. &c. æquilatero-triangular form, as in A in the 7. Scheme. If a fourth be joyn’d to them on either side as closely as it can, they four compose the most regular Rhombus consisting of two æquilateral triangles, as B. If a fifth be joyn’d to them on either side in as close a position as it can, which is the propriety of the Texture, it makes a Trapezium, or four-sided Figure, two of whose angles are 120. and two 60. degrees, as C. If a sixth be added, as before, either it makes an æquilateral triangle, as D, or a Rhomboeid, as E, or an Hexangular Figure, as F, which is compos’d of two primary Rhombs. If a seventh be added, it makes either an æquilatero-hexagonal Figure, as G, or some kind of six-sided Figure, as H, or I. And though there be never so many placed together, they may be rang’d into some of these lately mentioned Figures, all the angles of which will be either 60. degrees, or 120. as the figure K. which is an æquiangular hexagonal Figure is compounded of 12. Globules, or may be of 25, or 27, or 36, or 42, &c. and by these kinds of texture, or position of globular bodies, may you find out all the variety of regular shapes, into which the smooth surfaces of Alum are form’d, as upon examination any one may easily find; nor does it hold only in superficies, but in solidity also, for it’s obvious that a fourth Globule laid upon the third in this texture, composes a regular Tetrahedron, which is a very usual Figure of the Crystals of Alum. And (to hasten) there is no one Figure into which Alum is observ’d to be crystallized, but may by this texture of Globules be imitated, and by no other.

I could instance also in the Figure of Sea-salt, and Sal-gem, that it is compos’d of a texture of Globules, placed in a cubical form, as L, and that all the Figures of those Salts may be imitated by this texture of Globules and by no other whatsoever. And that the forms of Vitriol and of Salt-Peter, as also of Crystal, Hore-frost, &c. are compounded of these two textures, but modulated by certain proprieties: But I have not here time to insist upon, as I have not neither to shew by what means Globules come to be thus context, and what those Globules are, and many other particulars requisite to a full and intelligible explication of this propriety of bodies. Nor have I hitherto found indeed an opportunity of prosecuting the inquiry so farr as I design’d; nor do I know when I may, it requiring abundance of time, and a great deal of assistance to go through with what I design’d; the model of which was this:

First, to get as exact and full a collection as I could, of all the differing kinds of Geometrical figur’d bodies, some three or four several bodies of each kind.

Secondly, with them to get as exact a History as possibly I could learn of their places of Generation or finding, and to enquire after as many circumstances that tended to the Illustrating of this Enquiry, as possibly I could observe.