420 Bejjorts and Proceedings — British Association. 



I venture, however, to hope that the frontier between geology 

 and mineralogy is so ill-defined — if indeed a scientific frontier can 

 be said to exist — that the thoughts and occupations of one who has 

 confined himself to the study of minerals, and that rather in the 

 laboratory than in the field, are not alien to the interests of 

 Section C. 



Experimental Geology. 



A somewhat lamentable aspect of modern science is the vast array 

 of unorganised facts which are awaiting co-ordination ; this is too 

 often because they have been amassed without any definite idea of 

 the purpose which they may serve ; consequently it may happen 

 that laborious observations belonging to one science may fail to 

 attract the regard of a neighbouring science merely for want of the 

 mutual acquaintance which would make them serviceable to each 

 other ; and in these days of exclusive specialisation the introduction 

 which might lead to a happy union is, perhaps, not brought about 

 for years. None can be more fully alive to the importance of such 

 an alliance than those whose work lies on the borderland between 

 different sciences ; the mineralogist, for example, is in contact on the 

 one side with the experimental sciences of chemistry and physics, 

 and on the other with geology, which has scarcely yet entered the 

 experimental stage. He cannot fail to be impressed by the need of 

 the appeal to experiment on the geological side of the border, and it 

 is perhaps his duty to supply the want as far as lies in his power. 



Owing to this very need some of the most difficult problems in 

 geology are those concerned with the origin of minerals and of the 

 rocks which they compose. One need but recall the many tlieories 

 which have been held about the origin of mineral deposits, the filling 

 of metalliferous veins, the local concentration of certain minerals, the 

 distribution of various rock types, the existence of rock magmas of 

 diverse compositions, and the differentiation of their constituents. 

 Could the importance and difficulty of such problems be better 

 illustrated than in South Africa, and by its two most valuable 

 minerals, gold and diamond ? 



Now all these are problems in which direct appeal may, and 

 indeed must, be made to laboratory experiments ; the well-defined 

 minerals of which the earth's crust consists do not, after all, number 

 much more than 800, and of these many have already been 

 manufactured in the laboratory. Speculation upon the origin of 

 rocks and minerals should surely be controlled by the results of 

 experiments, and equally should experiment which is to be of service 

 to geology be guided by a knowledge of the problems to which it is 

 to be applied. It will be my object in the present Address to 

 illustrate these principles by examples drawn from recent ex- 

 perimental work which can be applied to geological problems, and 

 to indicate the course which such research is likely to pursue in the 

 immediate future. 



It seems to be sometimes expected of a Presidential Address that it 

 should contain a summary of the progress of a science during past 



