To this I answer, that that Hypothesis which the industrious Mersennus has publish’d about the slower motion of the end of a Ray in a denser medium, then in a more rare and thin, seems altogether unsufficient to solve abundance of Phænomena, of which this is not the least considerable, that it is impossible from that supposition, that any colours should be generated from the refraction of the Rays; for since by that Hypothesis the undulating pulse is always carried perpendicular, or at right angles with the Ray or Line of direction, it follows, that the stroke of the pulse of light, after it has been once or twice refracted (through a Prisme, for example) must affect the eye with the same kind of stroke as if it had not been refracted at all. Nor will it be enough for a Defendant of that Hypothesis, to say, that perhaps it is because the refractions have made the Rays more weak, for if so, then two refractions in the two parallel sides of a Quadrangular Prisme would produce colours, but we have no such Phænomena produc’d.
There are several Arguments that I could bring to evince that there are in all transparent bodies such atomical pores. And that there is such a fluid body as I am arguing for, which is the medium, or Instrument, by which the pulse of Light is convey’d from the lucid body to the enlightn’d. But that it being a digression from the Observations I was recording, about the Pores of Kettering Stone, it would be too much such, if I should protract it too long; and therefore I shall proceed to the next Observation.
Observ. [XVI]. Of Charcoal, or burnt Vegetables.
Charcoal, or a Vegetable burnt black, affords an object no less pleasant than instructive, for if you take a small round Charcoal, and break it short with your fingers, you may perceive it to break with a very smooth and sleek surface, almost like the surface of black sealing Wax; this surface, if it be look’d on with an ordinary Microscope, does manifest abundance of those pores which are also visible to the eye in many kinds of Wood, rang’d round the pith, both a in kind of circular order, and a radiant one. Of these there are a multitude in the substance of the Coal, every where almost perforating and drilling it from end to end; by means of which, be the Coal never so long, you may easily blow through it; and this you may presently find, by wetting one end of it with Spittle, and blowing at the other.
But this is not all, for besides those many great and conspicuous irregular spots or pores, if a better Microscope be made use of, there will appear an infinite company of exceedingly small, and very regular pores, so thick and so orderly set, and so close to one another, that they leave very little room or space between them to be fill’d with a solid body, for the apparent interstitia or separating sides of these pores seem so thin in some places, that the texture of a Honey-comb cannot be more porous. Though this be not every where so, the intercurrent partitions in some places being very much thicker in proportion to the holes.
Most of these small pores seem’d to be pretty round, and were rang’d in rows that radiated from the pith to the bark; they all of them seem’d to be continued open pores, running the whole length of the Stick; and that they were all perforated, I try’d by breaking off a very thin sliver of the Coal cross-ways, and then with my Microscope, diligently surveying them against the light, for by that means I was able to see quite through them.
These pores were so exceeding small and thick, that in a line of them, ¹⁄₁₈ part of an Inch long, I found by numbering them no less then 150. small pores; and therefore in a line of them an Inch long, must be no less then 2700. pores, and in a circular area of an Inch diameter, must be about 5725350. of the like pores; so that a Stick of an Inch Diameter, may contain no less then seven hundred and twenty five thousand, besides 5 Millions of pores, which would, I doubt not, seem even incredible, were not every one left to believe his own eyes. Nay, having since examin’d Cocus, black and green Ebony, Lignum Vitæ, &c. I found, that all these Woods have their pores, abundantly smaller then those of soft light Wood; in so much, that those of Guajacum seem’d not above an eighth part of the bigness of the pores of Beech, but then the Interstitia were thicker; so prodigiously curious are the contrivances, pipes, or sluces by which the Succus nutritius, or Juyce of a Vegetable is convey’d from place to place.
This Observation seems to afford us the true reason of several Phænomena of Coals; as
First, why they look black; and for this we need go no further then the Scheme, for certainly, a body that has so many pores in it as this is discover’d to have, from each of which no light is reflected, must necessarily look black, especially, when the pores are somewhat bigger in proportion to the intervals then they are cut in the Scheme, black being nothing else but a privation of Light, or a want of reflection; and wheresoever this reflecting quality is deficient, there does that part look black, whether it be from a porousness of the body, as in this Instance, or in a deadning and dulling quality, such as I have observ’d in the Scoria of Lead, Tin, Silver, Copper, &c.