Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/157

Rh small parcel of matter is able to tinge and diffuse it self over a very great quantity of the fluid dissolvent; or somewhat after that manner, as smoak, and such like minute bodies, or steams, are observ'd to tinge a very great quantity of air; onely this last similitude is deficient in one propriety, and that is a perpetuity or continuance in that state of commixture with the air, but the former does more neerly approach to the nature and manner of the air's being dissolv'd by this fluid or Æther. And this Similitude will further hold in these proprieties; that as those tinctures may be increased by certain bodies, so may they be precipitated by others, as I shall afterwards shew it to be very probable, that the like accidents happen even to the Air it self.

Further, as these solutions and tinctures do alter the nature of these fluid bodies, as to their aptness to propagate a motion or impulse through them, even so does the particles of the Air, Water, and other fluid bodies, and of Glass, Crystal, &c. which are commixt with this bulk of the Æther alter the motion of the propagated pulse of light; that is, where these more bulkie particles are more plentifull, and consequently a lesser quantity of the Æther between them to be mov'd, there the motion must necessarily be the swifter, though not so robust, which will produce those effects, which I have (I hope) with some probability, ascribed to it in the digression about Colours, at the end of the Observations on Muscovy-glass.

Now, that other Stones, and those which have the closest and hardest textures, and seem (as far as we are able to discover with our eyes, though help'd with the best Microscopes) freest from pores, are yet notwithstanding replenish'd with them, an Instance or two will, I suppose, make more probable.

A very solid and unflaw'd piece of cleer white Marble, if it be well polish'd and glaz'd, has so curiously smooth a surface, that the best and most polish'd surface of any wrought-glass, seems not to the naked eye, nor through a Microscope, to be more smooth, and less porous. And yet, that this hard close body is replenish'd with abundance of pores, I think these following Experiments will sufficiently prove.

The first is, That if you take such a piece, and for a pretty while boyl it in Turpentine and Oyl of Turpentine, you shall find that the stone will be all imbu'd with it; and whereas before it look'd more white, but more opacous, now it will look more greasie, but be much more transparent, and if you let it lie but a little while, and then break off a part of it, you shall find the unctuous body to have penetrated it to such a determinate depth every way within the surface. This may be yet easier try'd with a piece of the same Marble, a little warm'd in the fire, and then a little Pitch or Tarr melted on the top of it; for these black bodies, by their insinuating themselves into the invisible pores of the stone, ting it with so black a hue, that there can be no further doubt of the truth of this assertion, that it abounds with small imperceptible pores.

Now, that other bodies will also sink into the pores of Marble, besides unctuous, I have try'd, and found, that a very Blue tincture made in Rh