very conspicuous neer the knee, as in the cleft K K, when the Beard was dry; upon the discovery of which, I began to think, that it was upon the swelling of this porous pith upon the access of moisture or water that the Beard, being made longer in the midst, was streightned, and by the shrinking or subsiding of the parts of that Spongie substance together, when the water or moisture was exhal'd or dried, the pith or middle parts growing shorter, the whole became twisted.
But this I cannot be positive in, for upon cutting the wreath'd part in many places transversly, I was not so well satisfy'd with the shape and manner of the pores of the pith; for looking on these transverse Sections with a very good Microscope, I found that the ends of those transverse Sections appear'd much of the manner of the third Figure of the 15. scheme A B C F E, and the middle or pith C C, seem'd very full of pores indeed, but all of them seem'd to run the long-ways.
This Figure plainly enough shews in what manner those clefts, K and L divided the wreath'd Cylinder into two unequal parts, and also of what kind of substance the whole body consists; for by cutting the same Beard in many places, with transverse Sections, I found much the same appearance with this express'd; so that those pores seem to run, as in most other such Cany bodies, the whole length of it.
The clefts of this body K K, and L L, seem'd (as is also express'd in the Figure) to wind very oddly in the inner part of the wreath, and in some parts of them, they seem'd stuffed, as it were, with that Spongie substance, which I just now described.
This so oddly constituted Vegetable substance, is first (that I have met with) taken notice of by Baptista Porta, in his Natural Magick, as a thing known to children and Juglers, and it has been call'd by some of those last named persons, the better to cover their cheat, the Legg of an Arabian Spider, or the Legg of an inchanted Egyptian fly, and has been used by them to make a small Index, Cross, or the like, to move round upon the wetting of it with a drop of Water, and muttering certain words.
But the use that has been made of it, for the discovery of the various constitutions of the Air, as to driness and moistness, is incomparably beyond any other, for this it does to admiration: The manner of contriving it so, as to perform this great effect, is onely thus:
Provide a good large Box of Ivory, about four Inches over, and of what depth you shall judge convenient (according to your intention of making use of one, two, three, or more of these small Beards, ordered in the manner which I shall by and by describe) let all the sides of this Box be turned of Basket-work (which here in London is easily enough procur'd) full of holes, in the manner almost of a Lettice, the bigger, or more the holes are, the better, that so the Air may have the more free passage to the inclosed Beard, and may the more easily pass through the Instrument; it will be better yet, though not altogether so handsom, if insteed of the Basket-work on the sides of the Box, the bottom and top of the Box be join'd together onely with three or four small Pillars, after the manner repre-
