350 Professor Haussmami on Metallurgy Crystallography . 
on account of the smallness of the crystals. The crystals are 
transparent, of a vitreous lustre, very brittle, and cut glass. 
Before the blowpipe they form a white, bubbling, and opaque 
glass. From these characters we may draw the conjecture, that 
this scoria is almost wholly of an earthy nature, 
5. Arsenious Acid. 
Arsenious Acid belongs to a class of crystalline metallur- 
gical formations, produced by sublimation in many metallur- 
gical processes, where arseniferous minerals are melted. Tor- 
bern Bergman, in a work formerly quoted, in regard to the 
formation of crystals, mentions crystals of what is denominated 
White Arsenic, which is prepared artificially by a dry process. 
Born also takes notice of it ; he observes, that, on the surface of 
sulphur melted at Schmolnitz in Upper Hungary, arsenic was 
spontaneously produced of a white, clear, pellucid appearance, 
in solitary crystals of a pyramidal and octaedral form. Our 
countryman Beckman, states, in a new edition of the Crystallo- 
graphy of Romeus Insulanus, that this same crystalline sub- 
stance is produced in masses at the founderies of Goslar, of 
which I have given a more copious description in the journals 
of Moll. 
Most excellent specimens of crystals of white arsenic occur 
in many of the founderies in the Hartz. 
1. In masses,, where arseniferous minerals are roasted at the 
founderies of Goslar. 
2. In masses,, where plumbiferous and argentiferous ores 
are roasted at the founderies of Andreasberg. 
The crystals are formed either perfectly, or more or less im- 
perfectly. The perfect crystals are, 
1. Regular octahedron. 
% Wedge-formed octahedron. 
The crystals having a less perfect formation, are octahedrons, 
in the planes of which there are trilateral cavities, with ladder- 
formed sides. These cavities are analogous to those already 
described, as occurring in artificial galena ; and are sometimes 
so large, as to exhibit the appearance of a whole mass, composed 
of eight excavated tetraedrons, and the sides of which are fre- 
quently unequal ; nor does it rarely happen, that a solitary ex- 
cavated tetraedron occurs either with perfect planes, or one or other 
