20 
shaped fragments and portions consisting of waterworn pebbles, 
fragments of quartz, ferruginous sand, agate, &c. This matrix 
(gravelly alluvium) has been undoubtedly caused by the action 
of water and deposited on or between the fragments of the 
various trap rocks, and all the circumstances would tend to 
show that the country must have been submerged, and the 
matrix in which the diamonds lie must have been deposited in 
the run of the currents, lake, or body of water; or ice may have 
operated in depositing them in their present position; or again, 
it is a question to be settled whether they have originated in 
changes of the local strata; or, and still more probable, whether 
their existence has been brought about by the agency of the 
igneous rocks. The solution of this question has an importance 
higher than the settlement of a debatable matter of science. It 
is a consideration which may vastly aid the success of future 
diamond seekers. By knowing the original rock, its composi¬ 
tion is learnt, and if the diamonds have been broadcast over the 
district as a result of denudation or aqueous action, certain 
minerals will indicate the probability of their presence or 
absence in that precise locality. If for example they have been 
derived from the igneous rocks, agate or carnelian, as indica¬ 
tive of degradation of the Karoo beds, will not be essential 
accompaniments, but there will rather have to be looked for 
an assortment of minerals known to abound in metamorpbic 
rocks. Every person knows that the diamond is crystallized 
carbon, but its mode of formation is still a mystery. All that is 
known would go to show that its production is the result of the 
slow decomposition of some vegetable or bituminous material, 
an opinion which receives support from the fact that when the 
ash left by the incineration of the diamond is examined micro¬ 
scopically, it presents the remains of a vegetable structure. All 
attempts to obtain the gem by artificial means have failed, 
unless the recent statement made by Despretz is to be received. 
Tie says that he has obtained microscopic octobedra having the 
hardness of the diamond by the prolonged action of an induct¬ 
ive current on sugar charcoal, and also by the action of the 
electric current continued for six months on one of the chlorides 
of carbon. 
