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TRANSACTIONS. 199 
the small mine, St. Augustine’s, near the Central. Though this 
may be the result of a lateral thrust, it seems more simply ex- 
plained as the result of volcanic action. Hence if we suppose the 
above reasoning correct, the period of formation of the craters is 
fixed as the epoch of the deposition of the Kimberley shales by 
the occurrence of this dolerite contemporancously with the shales. 
The next point of interest is to know whether the diamondi- 
ferous blue earth occurs really zz st or has been washed in from 
above. I am strongly inclined to the latter view, and for the 
following reasons : 
1. The blue earth has no distinctively igneous appearance 
whatever. 
2. Though in the case of St. Augustine’s Mine the part of the 
blue near the edge of the pit is hardened, there is generally no 
sign of the blue having been ejected from below, and it certainly 
does not alter the rocks with which it is in contact. Usually 
speaking, those parts of the blue earth which are in contact with 
the surrounding strata are marked by a soft jumbled or “soapy” 
condition. 
3. Mr G. R. Lee, of Kimberley, shewed me a piece of lignite 
found in the blue earth, and he also told me that he had found 
limestone shells apparently unaltered in the blue earth. 
It appears therefore very probable that the blue earth has 
simply been brought in from above. There are even many reasons 
which tend to shew that the whole of the craters were subaqueous. 
The Kimberley shales have all the appeaiance of a deposit formed 
in deep and quiet water. One must also remember that they form 
the starting point of the fresh water beds of the Caroo formation 
and the Stormberg Beds (sandstones and coalmeasures), all of 
which are distinguished by a remarkable horizontality of the strata, 
and which attain a thickness of 2000 feet on an average. A glance 
at the map of South Africa shews a gigantic mountain chain 
within 80-120 miles of the coast and rising to an average height 
of 7000 feet above the sea. This range (the Drakensberg) includes 
such mountains as the Font aux’ Sourees, 10,000 feet ; the Giant’s 
Castle, 9657 feet; and Cathkin Peak, 10,357 feet. Now Kim- 
berley is only 4200 feet above the sea. The basin of the Vaal 
River in fact is bounded by the Drakensberg, then by a continuous 
series of mountain ranges, under different names (Stormbergen, 
Bamboesbergen, Kikvorschbergen, Nieuwveld, Roggeveld, Guaap, 
&c.), which run all round the southern corner of the continent at 
