Seite 27 [27]
OCR
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 coloured 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
