The variety, 'Which is of a dark jpurjdcj
pervading the whole mafs, is loofe and
friable.
That of one flrong blue vein is much
harder, very rich, and tranfparent.
Fluor in detached cubes, in the limeftone,
appearing a littid decotfipofed»
Fluor with metalic veins.
Fluor decompofing.
Fluor o f a fine green tinge.
O f a blue colour, in a mafs oFcryftallized
cubes, with elaftic or indurated bitumen.
Fluor in Gompact limeftone with galena,
in veins and fmall particles, filling up inters
ftices*
Fluor eryftallized irl cubes, upon born-
ftone or petrofilex.
Fluor in the cavities of corallöids.
Fluor with barytes, commonly called
tyger ftone, being opake, and full of dirty
brown fpots.
Having
Having thus given ati account of the
chief varieties of fluor, I fhall deferibe the
art of workmg it.
When it is intended to be worked into a
vafe, or the like article, a piece is feledtecl
fit for the purpofe ; and if after minute examination
it be found free fiom defe<St$, it
is carved with a mallet and duffel into a-
fpherical form, and then fixed on a chock with
an exceedingly ftrong cement. The chock
is then 'ferewed on the lath, a flow motion
is produced, and water continually drops
on the Hone, to keep'the tool cold, which
is at ‘firft applied with great care. This
todl is a piece of 'the bcfl fteel, about "two
feet Tong, and half an inch -fquare: it is
reduced to a point at each end, and tempered
to fnlt the -work. As'the furface becomes
fmoother, the tool is applied more
boldly, and the motion much quickened,
till