Section B.— CHEAIISTRY, GEOLOGY. METALLURGY, 

 MINERALOGY AND GEOGRAPHY. 



President of the Section — A. W. Rogers, j\LA., Sc.D., 



F.G.S. 



TUESDAY. XOJ^ EMBER i. 



The President delivered the following address : — 



" In examining things present, we have data from which to reason with 

 regard to what has been ; and from what has actually been, we have data 

 for concluding with regard to that which is to happen hereafter. Therefore, 

 upon the supposition that the operations of nature are equable and steady, 

 we find, in natural appearances, reasons for concluding a certain portion of 

 time to have necessarily elapsed, in the production of those events of which 

 we see the effects." 



So wrote James Hutton on an early page of his " Theory of 

 the Earth," which was published in 1785. That passage, and 

 others to the same purpose, clearly prove the speculative 

 character of the geological discussions of the time; otherwise 

 the method alluded to, which is the only one by which geology 

 can get a firm foundation, would not have required statement 

 in such a categorical form. 



Of all the sciences there is perhaps none in which speculation 

 can more readily run riot than geology, because it is so dififi- 

 cult to reconstruct in imagination all the circumstances which 

 govern any particular event recorded in the rocks. The 

 fashion, therefore, of working on uniformitarian lines that was 

 set by Hutton. and followed with such success by Lyell, was of 

 the greatest service to geology, even though it was attended by 

 the conspicuous disadvantage of suppressing enquiry into 

 things w4iich, by their nature, could not be explained by pro- 

 cesses open to observation. 



The essence of the uniformitarian theory is that only those 

 agencies which are known to be efficaceous in bringing about 

 changes in the earth's crust or on its surface can be called upon 

 to explain the meaning of the rocks. It is obvious that every 

 discovery which extends our knowledge of processes going on 

 upon the earth, in it, and outside it, if they affect the crust or 

 its surface, must come within the province of the theory. An 

 important assumption made by Hutton was that throughout 

 past times, of which we have records in the rocks, the agencies 

 at work to-day have not varied greatly from their present scale 

 of activity; it is this part of the theory that has met with most 

 opposition. 



It is my purpose on this occasion to review some of the re- 

 sults of geological work done in South Africa bearing on 

 the origin of certain very old rocks, the history of vulcanism, 

 and past climates, with the object of discovering whether they 

 necessitate any serious modifications of the uniformitarian 

 theory. 



One of the most interesting questions in geologv concerns 

 the origin of the rocks often called Archaean. They are schistose 

 and foliated rocks with a chemical composition comparable with 

 that of sedimentarv and igneous rocks, but their minute 



