222 prof. t. g. boxney on ceystallixe schists and theik 



5. Conclusions. 



If, then, we accept the identification of the Andermatt marble 

 with the Jurassic rock of the Urserenthal and of the Black- garnet 

 schists with the Jurassic " spotted rock " of the Lnkmanier and 

 Xufenen Pass, and (as a necessary consequence of these admissions) 

 of the upper group of schists with the Mesozoic rocks of other parts 

 of the Alps, we find ourselves inextricably involved in the following 

 dilemmas : — 



(1) That this upper group of schists, which, in all sections free 

 from suspicion, consists of highl}^ crystalline rocks, overlies the 

 rauchwacke, which, in the same region, is quite an ordinary lime- 

 stone. 



(2) That the rauchwacke, though underlying this group of schists, 

 contains fragments of more than one characteristic member of it, 

 identical in all essential respects. 



(3) That, if the admissions be correct, metamorphism takes place 

 in accordance with no principle and in obedience to no law. Eocks, 

 in regions of intense pressure, are sometimes highly metamorphosed, 

 sometimes, though with no appreciable mineral differences, are 

 practically unaltered. 



From these dilemmas I can see no way of escape, except by 

 denying the facts stated in this paper. On their substantial 

 accuracy I will stake my credit as a worker in science. Moreover 

 I must confess myself at a loss to understand how some of them 

 have been overlooked or ignored hy previous observers, and feel 

 justified in expressing my surprise that such slight and superficial 

 evidence has been held sufiicient to warrant the adoption and publi- 

 cation of hypotheses which, as a little reflection and some general 

 knowledge of the geology of the Alps would have quickly shown, 

 could not fail to land us in the gravest difiiculties. It would be 

 imprudent, in the present state of our kiiowledge, to prescribe 

 arbitrarily limits to the powers of Nature ; but it is justifiable to 

 generalize from one's own observations, when these not only have 

 been made with all possible care, but also are very considerable in 

 number. So I will venture to end this communication, already 

 perhaps too long, by stating that though I have been for years 

 familiar with Palaeozoic and still more with Mesozoic rocks of 

 diverse mineral characters in many parts of the Alps, including 

 districts where there have been great foldings, strange contortions, 

 and severe crushings, I have never seen a limestone which presented 

 any real resemblance to the marbles which are usually associated 

 with schists and gneisses, or a slate which was much more than a 

 phyllite, or which, if studied carefully, could not be distinguished 

 from an ordinary mica-schist *. But I have always found that 

 limestones, schists, &c., in the crystalline districts possessed cha- 

 racters, macroscopic and microscopic, in common, by which they 

 could be distinguished from members of the Palaeozoic and Mesozoic 

 series. Cases of difficulty do, no doubt, occasionally occur, but, so 



* I have seen numerous instances similar to those so well figured in Prof. 

 Heim's classic work ' Mechanismus der Gebirgsbildiing,' and have examined the 

 specimens exhibited in the Berne Museum and elsewhere. 



