It was nearly as hard as Flint, and resembled the Grain thereof in some Parts, would
easily cut Glass, could scarcely be scratched itself by a black hard Flint, and would a?
readily as any common Flint strike Fire against a Steel.
Its Closeness was evident when placed in some Positions ; for the Reason why
the Pores appeared darker than the rest of the Body, was then shewn, viz. because
they were filled with a darker Substance, and not because they were hollow.
Though kept some time red-hot in the Flame of a Lamp, rendered very intense
by a Blow-Pipe and a large Charcoal, it loft nothing of its Substance, but appeared as
solid as before, only somewhat darker. ‘Twas remarkable that it soon grew red-hot,
and neither consumed like Wood, nor cracked and flew like Flint.
Distilled Vinegar being dropped upon it, many such Bubbles were raised instantly, as
are observable when it corrodes Corals.
It was so brittle that one Blow of a Hammer would break off a Piece, and two or
three more reduce it to a Powder.
It felt also much colder than Wood, and much like other close Stones and Mi-
nerals.
An EXPLANATION of the EIGHTH PLATE
FIG. 1.
The Pores in Cork
THE Circular Figure we are now deseribing,
exhibits two of the thinnest Slices of
Cork that could be shaved off with a Penknife, made as sharp as possible, in or-
der to discover, by the Microscope, the Texture and Form thereof. And, upon Exami-
nation, they were found to be all cellular or porous, in the Manner of an Honey-comb,
but not so regular. The solid Substance was also very small, in Comparison of the Cavi-
ties ; for the Partition between the Cells were near as thin in Proportion to them, as the
slender Divisions in an Honey-comb are in Proportion to the Cells they separate.
The Cells of Cork are ranged like so many Rays tending from the Center or Pith of
the Tree outwards : They are not very deep, but resemble many little Boxes, made by
Numbers of Partitions dividing one long continued Pore, as is shewn by the Slice marked
B, which being a transverse Section, presents a View of the Pores opened lengthwise.
The Slice marked A, was shaved off the long Way of the Cork, and consequently
shews all the Pores cut asunder transversely ; but the solid Partitions between them ap-
peared not so thick as they are here represented.
Several of these Lines being numbered, about Threescore of the small Cells, placed
end-ways, were found, usually, in the Length of the eighteenth Part of an Inch : where-
fore the Length of an Inch must contain above a Thousand, a square Inch above a Mil-
lion, or 1,166,400 ; and a cubic Inch above twelve hundred Millions, or 1,259,712,000;
a thing almost incredible, did not our Microscope assure us of it by ocular Demonstration.
This Contexture, discoverable by the Microscope, proves the Lightness, of Cork to pro-
ceed, as it does in Wool, Spunge, Pumice-Stone, &c. from its having a very small Quan-
tity of solid Matter, extended into exceeding large Dimensions. It proves likewise, that
its Unaptness to suck in, and consequently its floating on the Surface of Water, is owing
to its whole Substance being almost filled with Air, inclosed in those innumerable little
Cells or Boxes above described, which being full already, are impenetrable to Water or
other Air. Its Springingness, its Ability of being compressed into half the Dimensions it
occupied before, and its Power of extending itself into the same Space, when suffered to
act again, may likewise be accounted for from the same Causes. It is also probable that
the Sides of, and Partitions between the Cells, may have in them an elastic Quality, as most
Kinds of Vegetable Substances have, and so help to restore themselves to their former
Position.
Common as Cork is, its Production is known but little, and therefore it may not be
unacceptable to give a short Account thereof.
In the South Parts of France, in Spain and Italy, there are several Species of what they
call the Cork-Tree. But the broad-leaved Sort, that is ever green, and affords the most
and best Cork, is a pretty tall Tree, bearing Acorns like an Oak, tho' with Leaves much
