PROF. T. G. BONNEY ON CRYSTALLINE SCHISTS, ETC. 18' 



13. On the Crystalline Schists and their Eelation to the Mesozoic 

 EocKs in the Lepontine Alps. By T. G. Bonney, D.Sc, 

 LL.D., P.E.S., E.G.S., Professor of Geology ia IlDiversity 

 College, London, and Pellow of St. John's College, Cambridge. 

 (Eead January 22, 1890.) 



Table op Contents. 



Introductory. 



1. Jurassic and crystalline rocks near Andermatt. 



2. The schists of the Val Piora, 



3. The Eauchwacke and its relation to the schists. 



(a) Val Piora sections. 

 {b) Val Oanaria section. 



4. The Jurassic rocks with included minerals and fossils. 



(«) Preliminary. 



{b) Sections on the Lukmanier Pass (Scopi and Alp Vitgira). 



[a) The Nufenen Pass. 



5. Conclusions. 



6. Appendix, with microscopic details. 



(«) The " Val Piora " schists. 

 lb) The Eauchwacke. 

 (c) The Jurassic rocks. 



At the close of the year 1888 I read before this Society a paper 

 " On two Traverses of the Crystalline Eocks of the Alps," in which 

 I maintained that these rocks could be arranged in certain fairly 

 definite groups, which exhibited a stratigraphical succession. On 

 this communication only two criticisms of importance were offered. 

 Of these one expressed a doubt of the value of the method which I 

 had adopted in my work ; the other affirmed that certain schists, 

 regarded by me as members of a very ancient series, probably 

 Archaean, had been demonstrated by the presence of Mesozoic fossils 

 to be of the latter age ; or, in other words, that, in the Alps, ordinary 

 sediments deposited in the Jurassic epoch had been subsequently 

 converted into true crystalline schists, a result of metamorphic 

 action which I had implicitly affirmed to be incredible. The former 

 criticism, which amounted to an assertion that the general suc- 

 cession of the Alpine rocks could only be ascertained by very 

 detailed mapping, in my opinion, indicated an imperfect knowledge 

 of the subject, while it was scientifically unsound and historically 

 incorrect. It indicated an imperfect knowledge, because, as a 

 matter of fact, a considerable part of the Alps has already been 

 mapped, not by irresponsible amateurs but by official surveyors, and 

 it was with tlie interpretation of these maps that I was largely con- 

 cerned ; and because it assumed tliat an impossibility could be 

 performed. As I have had the honour to fill the same position in 

 the Alpine Club that I have done in this Society, I may to affirm with- 



