[13]This Stone which is brought from Kettering in Northampton-Shire, and digg’d out of a Quarry, as I am inform’d, has a grain altogether admirable, nor have I ever seen or heard of any other stone that has the like.  It is made up of an innumerable company of small bodies, not all of the same cize or shape, but for the most part, not much differing from a Globular form, nor exceed they one another in Diameter above three or four times; they appear to the eye, like the Cobb or Ovary of a Herring, or some smaller fishes, but for the most part, the particles seem somewhat less, and not so uniform; but their variation from a perfect globular ball, seems to be only by the pressure of the contiguous bals which have a little deprest and protruded those toucht sides inward, and forc’d the other sides as much outwards beyond the limits of a Globe; just as it would happen, if a heap of exactly round Balls of soft Clay were heaped upon one another; or, as I have often seen a heap of small Globules of Quicksilver, reduc’d to that form by rubbing it much in a glaz’d Vessel, with some slimy or sluggish liquor, such as Spittle, when though the top of the upper Globules be very neer spherical, yet those that are prest upon by others, exactly imitate the forms of these lately mention’d grains.

Where these grains touch each other, they are so firmly united or settled together, that they seldom part without breaking a hole in one or th’other of them, such as a, a, a, b, c, c, &c.  Some of which fractions, as a, a, a, a, where the touch has been but light, break no more then the outward crust, or first shell of the stone, which is of a white colour, a little dash’d with a brownish Yellow, and is very thin, like the shell of an Egg:  and I have seen some of those grains perfectly resemble some kind of Eggs, both in colour and shape:  But where the union of the contiguous granules has been more firm, there the divulsion has made a greater Chasm, as at b, b, b, in so much that I have observ’d some of them quite broken in two, as at c, c, c, which has discovered to me a further resemblance they have to Eggs, they having an appearance of a white and yelk, by two differing substances that envelope and encompass each other.

That which we may call the white was pretty whitish neer the yelk, but more duskie towards the shell; some of them I could plainly perceive to be shot or radiated like a Pyrites or fire-stone; the yelk in some I saw hollow, in others fill’d with a duskie brown and porous substance like a kind of pith.

The small pores, or interstitia eeee betwixt the Globules, I plainly saw, and found by other trials to be every way pervious to air and water, for I could blow through a piece of this stone of a considerable thickness, as easily as I have blown through a Cane, which minded me of the pores which Des Cartes allow his materia subtilis between the aethereal globules.