102 
THE PRINCIPAL FLOOR. 
Each case, or separate compartment of the Horseshoe Case, 
will be briefly described, commencing at the south-east corner of 
the series. 
Case A. — Diamond. 
From the high refracting power of the diamond. Sir Isaac 
Newton conjectured that this beautiful gem might be an unctuous- 
body, and therefore combustible. Heated in oxygen gas, the 
diamond may readily be burned, producing only carbon dioxide, 
and leaving a small quantity of ash, whilst in the electric arc it 
has been converted into a coke-like mass, thus proving it to be 
only a peculiar form of carbon. 
Diamonds are found naturally crystallised, the forms always 
being related to the cube and the faces being often rounded, as seen 
in many of the crystals exhibited. Diamonds were discovered at 
a very early period in the East Indies, and most of the large his- 
torical diamonds were obtained from India, especially from the so- 
called Golconda mines. Early in the last century diamonds 
were discovered in Brazil, where they occur chiefly in a deposit 
called cascalho, consisting principally of fragments of quartz 
and ferruginous sand : a sample of this cascalho is shown. Both 
India and Brazil have, however, been overshadowed by the dis- 
covery of diamonds in unparalled abundance in South Africa. 
The first diamond was found in the Colesberg district in 1867„ 
and was sold for 5001 . ; a model of this stone is exhibited. 
Large numbers of diggers were soon attracted to the fields, and 
their labours rewarded by the discovery of vast numbers of 
diamonds, including many of unusual size. 
The “ river- diggings,” established at first in the gravels of the 
Yaal River, were soon abandoned for the “ dry diggings,” where 
diamonds were found embedded in an altered volcanic rock. 
The mines known as Kimberley. De Beers, Du Toits Pan, and 
Bultfontein, all close together, were discovered in rapid succession, 
and an interval of nearly 20 years elapsed before another dis- 
covery — that of the Premier mine — was made there. The 
diamonds occurred at first in “ yellow ground,” which when 
followed downward, passed into “ blue earth ” ; this is a volcanic 
product, apparently an olivine-diabase, much serpentinised, and in 
parts breociated, filling pipes which pass through shales, associated 
with eruptive rocks. All these mines are in Griqualand West, 
which forms part of Cape Colony ; but diamonds also occur 
elsewhere in South Africa, notably at Jagersf ontein, in the 
Orange Free State, a locality which yielded in 1893 a huge 
diamond, called The Excelsior, said to weigh nearly 970 carats. 
Many of the largest known diamonds which have acquired 
historic interest are represented by models, among which those 
of the celebrated Koh-i-noor claim especial attention. On the 
annexation of the Punjaub by the British Government, in 1840 3 
the civil authorities took possession of the Lahore treasury. 
