Profc-isor T. G. Bonne// — Schists in Lepontinc A/jis. 16-"5 



Passing now to the stratigraphy, I claim to have proved — 



(a) That the schistose and fossiliferous Jurassic rocks in the 

 Scopi and Nufeuen districts overlie the rauchwacke.' 



(b) That this rauchwacke (commonly a friable yellowish lime- 

 stone, sometimes including layers of gypsum, but without any 

 marked indications of metamorphism) often contains fragments of 

 crystalline rocks corresponding with those which are elsewhere 

 associated with the black garnet-bearing schists. Also, that this 

 rauchwacke differs conspicuously from the cr3'stalline limestone or 

 dolomite, which occurs both on the northern side of the Campolungo 

 Pass (south of the Val Bedretto) and in association with similar 

 dark schists above Binn in the Biunenthal. 



(c) That the rauchwacke generally overlies the group of ciystal- 

 line schists, and where it is apparently interstratified with them 

 a closer examination always suggests that it is a later rock ' nipped ' 

 in by overfolding and thrust faulting. 



(d) In the noted Val Canaria section, where, according to Professor 

 Heim, crystalline schists- are included in a fold of which an ordinary 

 rauchwacke forms the base, not only does this rauchwacke contain 

 fragments of more than one variety of the schists supposed to overlie 

 it, but also the band of black garnet-bearing schists occurs three 

 times, and the other beds are not in pairs. These facts prove 

 a simple fold to be impossible,' and if faults be once admitted the 

 key of Professor Heim's position is surrendered. 



In addition to this I have shown, from stratigraphical, chemical, and 

 microscopic evidence, that the schistose Jurassic rocks and this group 

 of schists, locally garnet-bearing (a group which I have examined 

 in many places from the Viso to the Gross Glockner, and to which 

 I refer in my papers as the 'Upper Schists'), are quite distinct one 

 from the other; the only possible confusion arising from s[)ecimeus 

 either badly preserved or in which their distinctive characters have 

 been locally obliterated by extreme pressure. This, however, 

 is no ground for asserting contemporaneity. In such rocks the 

 metamorphism has been destructive, not constructive. 



I pass, then, to the mineral differences. The group of schists, of 

 which the dark one containing garnets is a member, consists, as 

 I have shown elsewhere, of truly crystalline rocks, no less in the 

 Val Canaria section than in the rest of the Alps, and never affords 

 a trace of a fossil. Here and there in its dark schists are little 

 streaks of crystalline calcite. These to a lively imagination may seem 

 the ghosts of departed belemnites, but to a niore prosaic mind they 

 appear only a vein product. The rocks are true crystalline schists, 

 no <loubt of sedimentary origin, but greatly metamorphosed. They 



' (iuart. Jnurn. Gcol. Soc. vol. xlvi (1890), p. 219. and vol xlix (1893), p. 89. 



- I suppose troiii Avhat I liavo read that Professor Heim will rctiiso to call these 

 rocks crystalline scliists. If so, there is no crystalline schist— either garnot-micu, 

 calc-mica, stanrolitc-niica, or (luartz-mica schist— in any part ot the Alps that 



I know of. ,,,-.• M 1 i 



^ The situation ot tlie outcrops and their breadths make it impossihlo to escane 

 this ditficnlty by supposin.tr one black garnet schist to have been the top bed and to be 

 doubled back on itself. 



