1886.] Diamond-Mines of South Africa. 63 



whicli surrounds these fragments now, was in a fused state. Wher- 

 ever lava or trap at such a high temperature has filled out cracks or 

 holes in other rocks we find the adjoining rock altered, mostly fused 

 by the enormous heat acting on it. But the minerals of Kimberley 

 Mine show nothing of this kind. And then, how is it to be explained 

 that some fossil remains, as coal-bearing shales and shells have 

 l)een found imbedded in the blue ? To prevent any misapprehension, 

 I beg to state, that I do not mean to say that these fossils had been 

 originally deposited in the blue. They came most probably out of the 

 surrounding shales or from the surrounding country, but they have 

 been mixed with the blue stuff when it was fluid or soft, and they are 

 well preserved, as I have myself seen. Neither the wood nor the 

 shells would have resisted such a high temperature as the melted mass 



These important objections have led to another theory, which 

 considers the mineral to be an aqueous product, it having been 

 upheaved in a muddy state. As this mud- volcano theory appears to 

 be the prevailing opinion among mining men, I think it necessary to 

 examine a little closer the principal points of it, which have been put 

 forth by Mr. Chaper as follows: — 



1. The mineral, now called the ''blue," has been ejected as an 



aqueous mud. 



2. This mud possessed a low temperature. 



3. It was very thin and fluid, having mixed up with it all the gar- 



nets, pebbles, fragments of rocks, &c. 



4. The stuff which fills out now the interstices between these 



pebbles is a kind of serpentine, which was dissolved in the 

 water. 



5. The whole mass was not ejected at a single eruption, but at 



several intervals and in thin layers. 



6. The hillock which formerly covered the spot, where now Kimber- 



ley Mine is, was the cone of ejection of this mud- volcano. 



Points number one and two are supported by the occurrence of 

 unaltered fossils and fragments of rocks without any sign of fusion. 



The contention under 3, that the mud has been of a very great 

 fluidity, is proved by the fact of its having entered into very thin 

 crevices of some fragments of slate, found imbedded in it and origina- 

 ting evidently from the rocks which form the walls of the mine. 



To the fourth point I must object, as the serpentinic matter could 

 not have been dissolved in water. It was simply mixed with it, 

 forming a thin mud. 



For the support of the fifth point, Mr. Chaper mentions certain 

 lines in the blue, which apparently separate different layers, but 

 I do^not think that this conclusion is sufficiently proved. 



The assertion under number six I cannot admit at all. But before 

 showing that the formation of the hillock has taken place in a very 

 different way, I may mention another fact, which has remained 

 unexplained to the present day, namely the occurrence of small pebbles, 

 larger stones and huge boulders in the blue, the surfaces of which are 

 smooth, as if they had been for a long time in moving water before 

 they came to their present place. These pebbles are a puzzle to Mr. 

 Chaper as well as to other geologists. I find nowhere an attempt to 

 ;account for their presence in the mineral. I may therefore be allowed 

 to venture the following hypothesis thereon. 



VOL. IV. Q 



