are _flat_, _limber_,
_softer,_ and _less transparent_, and in twisting into a thread they joyn,
and lie so close together, as to lose their own, and destroy each others
particular reflections. There seems therefore three Particulars very
requisite to make the so drest Flax appear Silk also when spun into
threads. First, that the substance of it should be made more _clear_ and
_transparent_, Flax retaining in it a kind of opacating brown, or yellow;
and the parts of the whitest kind I have yet observ'd with the _Microscope_
appearing white, like flaw'd Horn or Glass, rather then clear, like clear
Horn or Glass. Next that, the filaments should each of them be _rounded_,
if that could be done, which yet is not so very necessary, if the first be
perform'd, and this third, which is, that each of the small filaments be
_stifned_; for though they be square, or flat, provided they be
_transparent_ and stiff, much the same appearances must necessarily follow.
Now, though I have not yet made trial, yet I doubt not, but that both these
proprieties may be also induc'd upon the Flax, and perhaps too by one and
the same Expedient, which some trials may quickly inform any ingenious
attempter of, who from the use and profit of such an Invention, may find
sufficient argument to be prompted to such Inquiries. As for the _tenacity_
of the substance of Flax, out of which the thread is made, it seems much
inferiour to that of Silk, the one being a _vegetable_, the other an
_animal_ substance. And whether it proceed from the better concoction, or
the more homogeneous constitution of _animal_ substances above those of
_vegetables_, I do not here determine; yet since I generally find, that
_vegetable_ substances do not equalize the _tenacity_ of _animal_, nor
these the _tenacity_ of some purified _mineral_ substances; I am very apt
to think, that the _tenacity_ of bodies does not proceed from the _hamous_,
or _hooked_ particles, as the _Epicureans_ and some modern _Philosophers_
have imagin'd; but from the more exact _congruity_ of the constituent
parts, which are contiguous to each other, and so bulky, as not to be
easily separated, or shatter'd, by any small pulls or concussion of heat.

* * * * *

Observ. IV. _Of fine waled Silk, or Taffety._

This[5] is the appearance of a piece of very fine Taffety-riband in the
bigger magnifying Glass, which you see exhibits it like a very convenient
substance to make B