i897. NOTES AND COMMENTS. 77 



Professor Bonney on Alpine Geology. 



The history of geology has been described as a succession of 

 nightmares. Thanks to the extreme difference of the methods em- 

 ployed in the different branches of the science, the experts on one part 

 of the subject, if exclusively specialists, are often quite unable to 

 understand the work of their colleagues in another. The crystallo- 

 graphic formulae of the petrologist are usually as unintelligible to the 

 palaeontologist as a page of Chinese. Hence theories proposed by 

 men of eminence in geology often become articles in the orthodox 

 creed of that science simply by the subscription of men who are 

 quite unable to check the methods or reasoning on which the theories 

 are based. Thirty years ago a plague of theories was fastened on the 

 shoulders of geology by that Old Man of the Sea, Eozoon, owing to 

 the advocacy of biologists who regarded chrysolite as the same thing 

 as chrysotile. Some years later came the great "schist question." 

 According to what was once the orthodox school, schists were rocks 

 produced by the alteration of sedimentary rocks belonging to various 

 ages. Palaeozoic, Mesozoic, and even Tertiary. When schists were 

 found sandwiched between fossiliferous rocks they were all regarded 

 as a series of beds of the same age, of which one layer has been 

 altered and the other left. Accordingly the present school of geolo- 

 gists has grown up saddled with a load of theories proposed to explain 

 away the eccentricities of "selective metamorphism." These theories 

 have been especially disastrous to geological work in mountain areas. 

 Instances quoted in support of the fashionable view from Nubian deserts 

 or from South American jungles, or based only on single traverses, 

 of complex mountain groups, carried no weight. The theory rested 

 in the main on the " Mesozoic schists " of the Alps. All the leading 

 Swiss geologists accepted the theory ; they coloured the official maps 

 of the Swiss survey in accordance with it, and taught it in the bulky 

 monographs that accompanied those maps. It thus had an immense 

 influence on the geological thought of the rest of Europe. When 

 sceptics doubted they were referred to the Beitrdge zur Geologischen 

 Kavte der Schweiz, and if they adduced facts inconsistent with the views 

 there promulgated, they were told that it was so much the worse for 

 the facts. 



During the last few years, there has come a complete change of 

 view as to the age of the Alpine schists, and a consequent change in 

 the interpretation of the whole geology of the Alps. The geologist to 

 whose teaching this revolution is mainly due is, unquestionably, 

 Professor T. G. Bonney, who on New Year's Day gave the Geologists' 

 Association, London, a summary of the results of his 27 visits to the 

 Alps. This lecture will no doubt shortly be published by the Associa- 

 tion, and our object here is to direct attention to what is sure to be a 

 clear and reliable outline of the fundamental facts of Alpine geology. 

 It was not to be expected that the Swiss geologists would immediately 

 admit the overthrow of the theory, which was once almost universally 



