Oldal 27 [27]
MINERALOGICAL REMARKS 297
pounds weight, but they all proved fufible. "This is probably the
* Verre volcanique en grains noirs, réunis par une Lave compaéle grife,”
of Mr. Born’s Catalogue Raifonné, page 449, and the loofe grains,
his Verre volcanique noir, en grains ifolés,” page 450.
Mr, Klaproth has been fo obliging as to analyfe this foffil for me
(I mean the pearly Matrix). He found it to {well up only moderately,
when heated, and lefs. than the other varieties of the fame foffil ; and
that a piece of it, in a clay crucible, after remaining in a wind furnace
for two hours, was not melted, and continued of the fame fhape; but
the colour was changed to a reddifh brown, and it had loft 44 per cent.
of its weight. Another piece of the fame, expofed.in.a clay crucible, to
the heat of a porcelain furnace, melted into a. whitifh grey glafs
with an even and polifhed furface : in the fra@ure, however, it was
full of fine froth-bubbles, fcattered with white, black, and oker colour¬
ed grains imperfectly vitrified, about the fize of millet feed ; from
whence the glafs had a variegated and fpotted appearance. Analyfed
in the wet way, it gave, E
Siliceous Earth 714
f
| Fe. Aivillae i
Weighed in the red hot flate, 4 en à 18%
KL. Calx of Iron I
927
The volatile parts loft in the fire _- 4
97
Lofs - 3
100
The
25