derived by the operations of water and weather on the vast 
regions drained by the Orange and Vaal rivers, and now in 
part represented by the Draakenherg, which supplies the major 
part of the Orange system, giving to it agate gravel from their 
amygdaloid volcanic rocks. But to the North, the waters of the 
Vaal rise from mountains having a different rock construction. 
It was moreover suggested by Dr. Bubidge, that the direct 
heat and pressure of volcanic dykes passing through coal beds 
might bring about a change of hydro-carbons producing pure 
crystallized carbon or diamond, as they have changed certain 
coal-seams in S. Africa and other places into coke and graphite. 
Now it has been seen that the trap rocks of the Kopjes at 
Klip Drift are of volcanic origin, and have passed through fis¬ 
sured strata to the lower formations of the district. . These low- 
lying formations are known to be a part of the great stratified 
formation which juts out S. of the Orange river basin in the 
Colesberg, Smithfield, and other districts, and which constitutes 
a large part of the interior of the colony. This formation is 
known as the Karoo formation from the Karoo desert, and 
consists of a series of shales and sandstones rich in places with 
reptilian remains, especially that remarkable two-toothed rep¬ 
tile the Dicynodon, also with fishes of the Palseoniscan type, 
with seams of lignite and coal, remains of coniferous trees, ferns, 
and other plants, while throughout their extent the strata are 
crossed by dykes of trap rock, and often overlain or intercalated 
with igneous rock. Here, then, are found some of the ele¬ 
ments demanded by the theory of Dr. Bubidge for the forma¬ 
tion of diamonds by volcanic interference. 
The difficulties which present themselves in solving the 
question of the original site of the diamonds are innumerable. 
If the theory of their formation be true, it will be seen that 
they may with reason be referred to several rocks, but whilst 
at the same time the disarrangement of rocks in this part of the 
world has been both extreme and extensive, the fact of the 
existence of the gem with material both waterworn and not 
waterworn materially complicates the matter. But all the cir¬ 
cumstances considered, it may be concluded that the three pro¬ 
bable sources of them are (1) Outcrops of old rocks lower in the 
