92 
THE PRINCIPAL FLOOR. 
British territory or not. A large collection of copper- ores and 
other minerals from Namaqualand occupies the upper part of 
the Case. But the visitor will probably turn from these to the 
series of specimens illustrating the extraordinary occurrence of 
polcl in the Transvaal. Many of the important mines of the 
Witwatersrand are here represented, and several specimens show 
distinctly the character of the stratified deposits in which the 
gold occurs. The famous “ banket ” is a conglomerate of quartz 
pebbles, united by a siliceous cement, containing more or less 
gold. Large specimens of free gold are not common, but some 
masses of exceptional character are here exhibited. 
In the lower part of the Case are specimens of the beautiful 
fibrous material known, when cut and polished, as “ South 
African Cat’s* eye.” This is a mineral representing fibrous 
crocidolite , but consisting in its present form essentially of 
quartz with oxide of iron. The bottom shelves are occupied 
with a series of specimens illustrating the occurrence of 
diamonds in the famous fields of Kimberley. The diamonds 
occur in an altered serpentinous matrix occupying pipes, believed 
to represent volcanic vents which have burst through the shales 
.and sheets of eruptive rock in the Karoo formation (p. 1 02). 
THE METALLURGICAL COLLECTIONS. 
In the recesses on each side of the room, at the southern or 
Jermyn Street end, the visitor will find six flat cases which are 
devoted exclusively to the illustration of metallurgical operations. 
These cases are placed, as far as convenient, in front of the wall- 
cases containing the corresponding ores whose metallurgical 
treatment is here illustrated ; the series of iron-smelting pro- 
ducts, for example, being arranged immediately in front of the 
British iron ores. The processes illustrated in these Cases, 
although for the most part British, are by no means exclusively 
so; specimens from foreign works being, in many instances, 
placed by the side of our own productions for purposes of 
comparison and illustration. 
Copper-Sm elting. 
Table Case 40. — The ore when raised from the mine may be 
mixed with other metallic minerals or with earthy substances, 
and it has, therefore, as a first operation, to be freed as much as 
possible from these by a process of dressing. In the boxes in 
this Case are shown the ores in their various stages of preparation 
until they pass into the hands of the smelter. 
The process of copper-smelting, as conducted about the year 
1840, at Messrs. Vivian’s works at Swansea, in South Wales, is 
here fully illustrated. The dressed ore having been calcined in 
a reverberatory furnace was fused to the condition of coarse 
metal, which after calcination, was melted with certain 
