Vol. 54.] WITWATEESEAND AND OTHER DISTRICTS IN S. TRANSVAAL. 99 



Hill Series, and the latter dipping in towards the granite. The ex- 

 planation of this inverted sequence is to be sought in the existence 

 of a series of parallel strike-faults along which each successive 

 older series has been thrust up and over the younger beds. The 

 beds are highly tilted, and the outcrop of each series forms a distinct 

 range of hills. The fault-planes are masked by vast outpourings 

 of igneous rock, which probably followed closely on the dynamic 

 disturbances. 



In conclusion, I have only to add that in writing this paper I 

 have endeavoured to give an accurate account of facts as they 

 appeared to me, and have purposely avoided going into theoretical 

 or controversial matters. Consequently, among other things, the 

 interesting question as to the mode of origin of these formations, 

 whether by oceanic, lacustrine, or fluviatHe action, I have pre- 

 ferred to leave for others to settle. 



EXPLANATION OF PLATE VI. 



Geological Map of the Southern Transvaal, on the scale of about 11^ miles to the 

 inch ^ ; general section across the Witwatersrand from the Magaliesberg 

 through Johannesburg and the Nigel Mine ; and section from the 

 Gatsrand across the Yaal Eiver to Parys. 



Discussion. 



The President congratulated the Author on his important com- 

 munication, and asked whether there was any fossil evidence to show 

 the age of the beds under those of Permo-Carboniferous age. The 

 unconformities were important, and might indicate that there were 

 rocks in the area older than those of Palaeozoic age. Would it not 

 be better to avoid using the term ' Primary ' for crystalline rocks 

 suggested to be of ' Archaean ' age ? 



Mr. C. Dawson pointed out the great lithological resemblance of 

 the specimens on the table from the Hospital Hill Series to some 

 of the fiuviatile rocks of the English Wealden group ; particularly 

 to the lower beds of the Hastings Sands and Ashburnham group. 

 The Cape Series, of course, was a much older formation and 

 had suffered change, but the rocks of the Hospital Hill Series 

 appeared to have suffered least. He thought that palaeontological 

 evidence of the age of the Cape Series should be specially sought 

 for in the Hospital Hill Beds. 



Prof. Le Neve Poster said that he considered that all persons 

 interested in gold-mining were much indebted to the Author for his 

 very valuable contribution to our knowledge of the geology of a 

 great gold-bearing region. He desired information upon two 

 points : (i) whether the conglomerate beds on the southern side 

 of the synclinal are as rich in gold as those which have been so 

 largely worked on the northern side ; and (ii) what surface-iudica- 



^ [This map is published in colours, on the scale of 4| miles to the inch, by 

 Mr. E. Stanford, Cockspur St., S.W.] 



h2 



