1857.] RUBIDGE — NAMAaU ALAND. 237 



such facts and suggestions as an extensive journey among these de- 

 posits, and those of a different class (in the northern district) which 

 I shall presently describe, has presented to me, — premising that in 

 this part of the country, as far as my observation goes, it is only in 

 the axes of disturbance that deposits of metal have taken place. A 

 spot of granite, about the size of my hand, surrounded by silicate of 

 copper in quartz, on the road to Kok Fontein, is the only exception 

 I am acquainted with ; and even here the change of country may be 

 said to have commenced, though one metallic axis at least does occur 

 beyond it. 



That the deposit of metals is in some way connected with the 

 passage of water through the rocks is shown by several facts. 1st. At 

 Van-der-Stell Mine, which is a shaft sunk by a Governor of the Cape 

 (of that name) in 1680, a deposit of dendriform silica coloured with 

 silicate of copper lines the inner wall of the shaft (see specimen 97). 

 2ndly. My friend Dr. Atherstone found the jaw of a Dasje {Hyrax 

 Capensis) stained green with silicate of copper ; and at Spectakel 

 Mine a frog was found, in a dried state, coloured by the same mineral. 

 The waters of this country are generally brack, containing chloride 

 of sodium in considerable quantities (all the felspar is soda-felspar). 

 Then the decomposition of the felspar, its colouring by oxides and 

 silicates, and its conversion into clay, are, I think, evidently the 

 results of water-action. As to the question, which of the mineral 

 constituents of the rocks first gives way, I hope the specimens here- 

 with sent for illustration will put geologists at home in as good a 

 position for judgment as myself. The water seems to me sometimes 

 to penetrate between the layers of mica, conveying with it the copper ; 

 and, from the position so taken up, to have attacked the felspar in 

 some cases ; but in others the felspar seems to have undergone con- 

 siderable change while the mica is intact. Again, the quartz appears 

 to be the first to suffer in some instances, and to be the last in 

 others. 



Relative elevation of mines. — The different degrees of elevation 

 of the several deposits of ore do not appear to me to exert any 

 marked influence on them. At Springbok the mine is about 3000 

 feet above the sea, and, perhaps, 600 above the adjacent plain ; at 

 Concordia the elevation is about the same, but the " run" is on a 

 plain, and in a hill of slight elevation. At Henkries it is on a plain, 

 and these are all productive places. 



At Rietberg the run is near the summit of a mountain 4500 feet 

 high ; at Spectakel the elevation is, I think, 800 feet above the sea- 

 level, at the foot of a high hill. 



Other agencies besides vjater. — What effect terrestrial thermo- 

 electricity and its consequent magnetic phaenomena may have on 

 these deposits, I know not. These metalliferous rocks generally 

 run nearly in an east and west direction, that is with the strike 

 of the country ; but Spectakel is, I believe, a N.W. "run," though 

 there is some obscurity about it. I should not wonder if it 

 turns out, like Nababeeb, to be a meeting of two axes. I found 

 the walls of two of the cuttings on the Concordia property affect 



