C. M. Wetherill on the Crystalline Nature of Glass. 21 
3. A large mass of blackish green glass, with prismatic erys- 
tals singly and in aggregations, also fibrous crystals in globular 
tu The color of the crystals is dirty yellow, passing into 
green; their luster pearly. They had a rhomboidal section, 
and were a line in length by one-eighth of a line in thickness, 
4. A bluish green English glass, containing tufts of needles 
uniting to globules of one and a half lines in diameter. 
. A glass flux, of red and green color, containing a large 
quantity of small four-sided prisms, solitary, and in tufts. The 
prisms were transparent, and of the same color as the glass, so 
that they could only be distinguished by the different degree of 
their refraction and that of the matrix. 
6. A vitreous iron slag, of bottle-green color, containing per- 
fect cubes of whitish tinge and pearly luster; also feathery 
crystals. 
_ 1. Another specimen of iron ore slag, similar to the last; but 
in which the sa are larger, of nearly the color of the glass, 
more equally diffused through the mass. . 
Tn a similar slag the cubes were of olive-green color, and in an- 
other specimen the cubes were s and accompanied by feath- 
and apparently homogeneous, yielded crystals b; ful 
Stehing. Ordi : window a 7 similar csyatala which 
Were of the form of : . ee 
