44 
NORTH GALLERY. 
[upper 
in this Case. It is remarkable for containing crystalline calcium 
sulphide, associated with Enstatite and Augite. 
In Case B. are displayed, on the left extremity of the Case, the 
Siderolites, while the rest of the space is occupied by the Aero-siderites. 
The former are masses of meteoric iron containing stony matter ; the 
latter consist of the metallic alloys of iron and nickel with small 
amounts of other metals, known as " meteoric iron.'' They also contain 
mechanical admixtures of compounds of these metals with phosphorus, 
and also with sulphur. Among the specimens of the former class, is 
the mass found at Breitenbach in Bohemia, in 1861. It contains Silica 
crystallised in the orthorhombic system, associated with a ferriferous 
Enstatite (Bronzite), that is in some cases well crystallised. The 
crystalline structure of the meteoric iron masses is effectively shown 
by the etching of their polished surfaces. On the north side of this 
room is seen the vast mass of meteoric iron found at Cranbourne, 
near Melbourne, in Australia, presented by Mr. Bruce, of Inverqu- 
homery, and weighing above tons. At the east end of the gallery 
is one weighing l,4001bs., presented by Sir Woodbine Parish, found 
on the Gran Chaco, South America. 
The Collection of Minerals is arranged in four principal Divisions, 
These are — 
Division I. The Native Elements. Cases 1, 2, 3, 4 (i.) 
Division II. The Compounds of Metals, with Elements of the Arsenic 
Group (the Arsenoids, viz. Bismuth, Antimony, and 
Arsenic) ; or with elements of the Sulphur Group (the 
Thionids, viz. Tellurium, Selenium, and Sulphur); or 
with elements belonging to both groups. Cases 4 (ii.) 
to 12 inclusive. 
Division III. The Compounds of Metals with elements of the Chlo- 
rine Group (the Halogen elements — Iodine, Bromine, 
Chlorine and Fluorine). Cases 13 and 14. 
Division IV. Compounds of elements with Oxygen. Cases 15 to 60. 
These Divisions are again subdivided into sections and classes, the 
latter embracing the minerals which fall under the same general 
chemical denomination ; as, for instance, the salts of the same acid or of 
a group of acids chemically and crystallographically equivalent to each 
other. Each class is further separated into distinct chemical series, 
the minerals included in any series being such as are designated by 
the same or equivalent typical formulae. Subordinated to this chemical 
system of classilication is the final distribution of the several homotypical 
species of each chemical series, into distinct crrjstaUographic series, 
arranged according to the crystalline system to which they belong ; the 
order of sequence of these systems being — Ist, the Cubic System ; 2nd, 
the Dimetric or Pyramidal System ; 3rd, the Trimetric or Ortho- 
