Micrographia, by Robert Hooke

Observ. xi. Of Figures observ'd in small Sand.

Sand generally seems to be nothing else but exceeding small Pebbles, or at least some very small parcels of a bigger stone; the whiter kind seems through the Microscope to consist of small transparent pieces of some pellucid body, each of them looking much like a piece of Alum, or Salt Gem; and this kind of Sand is angled for the most part irregularly, without any certain shape, and the granules of it are for the most part flaw'd, through amongst many of them it is not difficult to find some that are perfectly pellucid, like a piece of clear Crystal, and divers likewise most curiously shap'd, much after the manner of the bigger StiriƦ of Crystal, or like the small Diamants I observ'd in certain Flints, of which I shall by and by relate; which last particular seems to argue, that this kind of Sand is not made by the comminution of greater transparent Crystaline bodies, but by the concretion or coagulation of Water, or some other fluid body.

There are other kinds of courser Sands, which are browner, and have their particles much bigger; these, view'd with a Microscope, seem much courser and more opacous substances, and most of them are of some irregularly rounded Figures; and though they seem not so opacous as to the naked eye, yet they seem very foul and cloudy, but neither do these want curiously transparent, no more than they do regularly figur'd and well colour'd particles, as I have often found.

There are multitudes of other kinds of Sands, which in many particulars, plainly enough discoverable by the Microscope, differ both from these last mention'd kinds of Sands, and from one another: there seeming to be as great variety of Sands, as there is of Stones. And as amongst Stones some are call'd precious from their excellency, so also are there Sands which deserve the same Epithite for their beauty; for viewing a small parcel of East-India Sand (which was given me by my highly honoured friend, Mr. Daniel Colwall) and, since that, another parcel, much of the same kind, I found several of them, both very transparent like precious Stones, and regularly figur'd like Crystal, Cornish Diamants, some Rubies, &c. and also ting'd with very lively and deep colours, like Rubys, Saphyrs, Emeralds, &c. These kinds of granuls I have often found also in English Sand. And 'tis easie to make such a counterfeit Sand with deeply ting'd Glass, Enamels and Painters colours.

It were endless to describe the multitudes of Figures I have met with in these kind of minute bodies, such as Spherical, Oval, Pyramidal, Conical, Prismatical, of each of which kinds I have taken notice.

But amongst many others, I met with none more observable than this Schem. 5.
Fig. X.
pretty Shell (described in the Figure X. of the fifth Scheme) which, though as it was light on by chance, deserv'd to have been omitted (I being unable to direct any one to find the like) yet for its rarity was it not inconsiderable, especially upon the account of the information it may afford us. For by it we have a very good instance of the curiosity of Nature in another kind of Animals which are remov'd, by reason of their minuteness, beyond the reach of our eyes, so that as there are several sorts of Insects, as Mites, and others, so small as not yet to have had any names; (some of which I shall afterwards describe) and small Fishes, as Leeches in Vineger; and smal vegetables, as Moss, and Rose-Leave-plants; and small Mushroms, as mould: so are there, it seems, small Shel-fish likewise, Nature shewing her curiosity in every Tribe of Animals, Vegetables, and Minerals.

I was trying several small and single Magnifying Glasses, and casually viewing a parcel of white Sand, when I perceiv'd one of the grains exactly shap'd and wreath'd like a Shell, but endeavouring to distinguish it with my naked eye, it was so very small, that I was fain again to make use of the Glass to find it; then, whilest I thus look'd on it, with a Pin I separated all the rest of the granules of Sand, and found it afterwards to appear to the naked eye an exceeding small white spot, no bigger than the point of a Pin. Afterwards I view'd it every way with a better Microscope and found it on both sides, and edge-ways, to resemble the Shell of a small Water-Snail with a flat spiral Shell: it had twelve wreathings, a, b, c, d, e, &c. all very proportionably growing one less than another toward the middle or center of the Shell, where there was a very small round white spot. I could not certainly discover whether the Shell were hollow or not, but it seem'd fill'd with somewhat, and 'tis probable that it might be petrify'd as other larger Shels often are, such as are mention'd in the seventeenth Observation.

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