Another of these drops I began to grind away at the smaller end, but had
not worn away on the stone above a quarter of an inch before the whole drop
flew with a brisk crack into sand or small dust; nor would it have held so
long, had there not been a little flaw in the piece that I ground away, as
I afterwards found.

Several others of these drops I covered over with a thin but very tuff skin
of _Icthyocolla_, which being very tough and very transparent, was the most
convenient substance for these tryals that I could imagine, having dipt, I
say, several of these drops in this transparent Glue whilst hot, and
suffering them to hang by a string tied about the end of them till they
were cold, and the skin pretty tough; then wrapping all the body of the
drop (leaving out only the very tip) in fine supple Kids-leather very
closely, I nipped off the small top, and found, as I expected, that
notwithstanding this skin of Glue, and the close wrapping up in Leather,
upon the breaking of the top, the drop gave a crack like the rest, and gave
my hand a pretty brisk impulse: but yet the skin and leather was so strong
as to keep the parts from flying out of their former posture; and, the skin
being transparent, I found that the drop retained exactly its former figure
and polish, but was grown perfectly opacous and all over flaw'd, all those
flaws lying in the manner of rings, from the bottom or blunt end, to the
very top or small point. And by several examinations with a _Microscope_,
of several thus broken, I found the flaws, both within the body of the
drop, and on the outward surface, to lye much in this order.

Let AB in the Figure X of the fourth Scheme represent the drop cased over
with _Icthyocolla_ or _Isinglass_, (by being ordered as is before
prescribed) crazed or flawed into pieces, but by the skin or case kept in
its former figure, and each of its flawed parts preserved exactly in its
due posture; the outward appearance of it somewhat plainly to the naked