48 
NORTH GALLERY. 
[UPPER 
Div. 1. Of Sulphur, large and splendid yellow crystals are exhibited from 
Case i. Conil, near Cadiz, and fine specimens from Sicily. The glazed front 
of Case ^ contains specimens belonging to tliis division, of extra- 
ordinary size and beauty. 
Div. 11. Division II. Compounds of the Arsenoid and Thionid Elements. 
Cases 4 (ii.) 
to 10 (i.) Leaving the native elements, we enter upon minerals which are the 
products of the chemical combination of the elements with each 
other; but the transition is not an abrupt one. The alloys, or mix- 
tures of metals of one and the same group, were associated in the 
lirst division with the metallic elements that compose them. But 
where metals belonging to distinct chemical groups are combined, they 
cannot be classed with the free elements. Such are the combinations 
of Arsenic, Antimony, and Bismuth with metals of other groups, and 
they (the arsenides, antimonides, &c.) accordingly take their places tis 
the tirst section of Division II and will be found arranged in the latter 
half of Case 4. 
Next in order to these are placed, as a second section of Divisioii 
II., the compounds of metals with the " thionid elements ; " and 
accordingly the tellurides, selenides, and sulphides are displayed in 
Cases 5 to 9 inclusive. 
These are succeeded by a third section of this division, namely, by 
Minerals to form which compounds belonging to each of the former 
sections are combined together. 
These three sections may be severally represented by their promi- 
nent members, the arsenides, the sulphides, and the arseno-sulphides. 
Section i. The first of these sections comprises the cuprous arsenides, such 
Case 4 (ii.) as Domeykite, the tricuprous arsenide ; also, the antimonide of 
Silver or Dyscrasite, diargentous antimonide. Besides these there 
are included in this section several compounds of Iron, Cobalt, and 
Nickel. Nickeline, called also " Copper-Nickel," from its colour, is a 
rhombohedral mineral, the nickel arsenide. Chloanthite is the nickel 
diarsenide and Smaltine, or " tin-white Cobalt," the cobalt diar- 
senide, of which Saflflorite is a variety, containing Iron in place of a 
part of its Cobalt. These minerals are cubic in crystallisation, but 
some of the substances which constitute them are also found in 
orthorhombic forms, affording examples of dimorphism. Thus the 
nickel diarsenide, when thus occurring in crystals of the orthorhombic 
system, is the mineral Rammelsbergite (of Dana), and Leucopyrite is 
a corresponding iron diarsenide. 
In this section is also included the cobalt triarsenide, Skutterudite. 
Section ii. The second section includes the various compounds of Sulphur. 
Selenium, or Tellurium — the Thionid elements — with the metals, 
Silver, a monad element, and Copper, a metal that in one group of its 
salts plays the part of a monad element, contribute to form a small 
group in this section of the type S. Eucairite is a selenide of Silver 
and Copper, and Crookesite is a selenide of Copper and Thallium. 
