732 MR. E. H. RASTALL ON THE GEOLOGY OF [N"oV. I9II, 



In conclusion, I have much pleasure in expressing my indebted- 

 ness to those gentlemen whose kind co-operation did so much 

 to render this work possible : to Dr. Melle, of Robertson, and 

 Mr. J. O'Connor, of Ashton, I owe a debt of gratitude for hospi- 

 tality and help in the field ; but above all, my thanks are due to 

 Dr. A. W. Rogers, on whose suggestion the work was undertaken, 

 and without whose help and encouragement it could not have been 

 carried out. To these and other friends who have aided me by 

 advice and criticism, I tender my most hearty thanks. 



EXPLANATION OF PLATE LI. 



Geological map of the neighbourhood of Worcester (Cape Colony), on the 

 scale of 1*8 miles to the inch, or about 1 : 115,000. 



Discussion. 



Mr. G. W. Lamplugh said that, for him, the chief interest of the 

 paper lay in the statements regarding the relation of the Enon 

 Conglomerate to the Worcester Fault. He paid a flying visit 

 to the Worcester district six years ago under the guidance of his 

 friend Dr. A. W. Rogers, and he then gathered, without, however, 

 himself seeing the evidence, that the Enon Conglomerate was 

 known to rest directly upon the Malmesbury rocks north of the 

 fault and to contain pebbles from these rocks. This implied that 

 the fault was believed in the main to be pre-Enon, though it was 

 recognized that there were minor movements along it at a later date. 

 Important conclusions as to the geological history of South Africa 

 generally had been based on this supposed relationship, which 

 was now challenged. If the Author was able to prove that 

 the previous investigators were wrong in their observations, he 

 had done good work in South Africa ; but, unless his evidence was 

 perfectly clear, he must be prepared for sharp criticism, as the 

 matter was of far-reaching consequence. 



Dr. J. W. Evans thought that the Worcester-Swellendam Fault 

 might be an ' isostatic ' fault, determined by the gradual rise of the 

 high ground on the north-east and depression of the sea-floor on 

 the south-west, as the former was worn down by subaerial agencies 

 and the resulting material accumulated on the latter. It often 

 happened that a certain amount of basement-conglomerate occurred 

 on the upthrow side of such a fault, and that might be the case 

 near Worcester, even if the movement continued after the depo- 

 sition of the Enon Conglomerate. With reference to the conflict 

 of evidence as to the occurrence of Malmesbury rocks in the 

 conglomerate, he suggested that, even on the supposition that the 

 greater portion of the conglomerate was deposited before these 

 rocks were laid bare, some of it might date from a later period 

 when they were exposed at the surface. 



The Author, in reply to the points raised by Mr. Lamplugh, 

 pointed out that post-Cretaceous faulting did not necessarily imply 



