50 PRESIDEXTIAL AJ)]mESS SECTIOX B. 



faulting', or the iutrusion of ig'ueous rock subsequent to tlie 

 deposition of the ore, which may result in all kinds of 

 disturbances and displacements. These constitute a very 

 important branch of the study of ore deposits, and are one 

 of the most frequent occasions for g-eological assistance to 

 be called in by those responsible for the conduct of mining 

 operations. In all cases of discontinuity, whether due to 

 faults or intrusions, or merely the result of the circumstances 

 imder which the ore was originally deposited, the important 

 point to decide is whether there is a chance of jiicking up 

 the ore-body again or not. The mining geologist must find 

 out whether the displacement is large or small ni amount and 

 indicate its direction, or, if there is no displacement to account 

 for the pinching out of the lode, he must give an opinion 

 as to whether the association of the pay-ore with particidar 

 geological features is such as to warrant the expectation of 

 encountering fresh shoots along the strike or in depth. There 

 are even cases where perfectly distinct ore-bodies may be 

 presumed to recur regularly in conjunction Avith special 

 structures — a well-known example of this is provided by the 

 " saddle reefs " of Bendigo, in Australia. 



I have no desire to labour these points on the present 

 occasion, nor do I propose to deal with such strictly geological 

 problems in connection with mining as the location of con- 

 cealed coal seams or oil pools. It will be sufficient to point 

 out that the kind of work rec[uired in the investigation of 

 the mineral resources of a country is far more closely allied 

 with that necessary to lead to success in drilling for oil than 

 is generally realised, although in South Africa it is more 

 obvious than in many other countries. Por instance,, the 

 definite location of the Rand " Main Reef " series in the 

 most remote district would clearlv justify the expenditure 

 of capital to open it up on some scale. The mere identification 

 of a particular rock as similar in every respect to another 

 already known as an ore-carrier is, in fact, a most useful 

 piece of information, and should lead to close examination 

 of its outcrop. Then, again, the determination of the various 

 periods of ore deposition may be of great assistance to those 

 in search of valuable minerals, even if only by warning the 

 prospector not to waste his time on rocks laid down or 

 intruded, as the case may be, subsequent to the last period 

 of mineralisation. These periods may, of course, differ for 

 different metals — a fact which must be clearly borne in mind. 

 It will be seen that theory does not enter at all into most of 

 these questions, or only in very small degree. Tor instance, 

 we should bore for the Main Reef just_ the same, whether 

 we considered its gold as alluvial, following Gregory, Mellor 

 and others, or as of magmatic origin in the way that Horwood 

 contends. 



In conclusion, I may briefly refer to the fact that 

 industrial progress is in some degree directly bound up with 

 the conduct of mining operations. The modern tendency is 

 undoubtedly more and more for the mine to become other 

 than a mere producer of raw material. In America especially 



