of the Lepontine Alps. 19 



under § I. Insignificant amounts of zincblende, galena, and pyrites 

 have been found in the same gneiss, not only at the surface (mining 

 trials in Val Cadlirao), but also in the tunnel at 3250-70, 3376, 

 3955 m. S., and at 4410 m. N. The zincblende formerly found near 

 Hospenthal (" im Saum ") and, together with mispickel, in the 

 Tiefthal near Meitschlingen, on the north side of the Gothard, may 

 also appertain to the same micaceous gneiss, as also that near St. 

 Nazaro on the Lago Maggiore, where some small adits have been 

 commenced in former times. 



4. The fourth group of crystalline schists, comprising transition 

 rocks between the gneiss-formation and the mica-schist formation, 

 has already been mentioned in connexion with the last named (§ IL). 

 The Ursern gneiss of the north side, and the felspathic mica schists 

 of the Scipsius (south side) were passed in the tunnel between 

 2000—4300 m. N. and 1850—3200 m. S. respectively ; the former 

 enveloping the troughs of the Altkirche limestones and of the 

 sericitic schists with the black schists of the Oberalp road. The 

 appearance of slaty gneiss or felspathic mica schist northward ,and 

 southward from the St. Gothard at Gurtnellen (probably also near 

 Amsteg), in the Ticino valley south and west from Faido, between 

 the Moesa and Bellinzona, at the foot of Mount Ceneri is recorded 

 on plates ii. vi. viii. x. and on the summary profile of the geological 

 map. Whilst the Ursern gneiss north of the Altkirche limestones 

 is a genuine slaty felspar-gneiss, it has, south thereof, more relation 

 with mica schist. Sericitic mica (besides the magnesian) and inter- 

 calations of quartzitio and gray-green micaceous beds indicate an 

 analogy between these rocks on both sides of the limestones ; but I 

 should not be opposed to a separation of the same, if the deciphering 

 of the geological structure of the Ursern valley would thereby be 

 promoted. The felspathic mica schist of the Scipsius (south side) 

 differs from the Ui'sern gneiss in containing abundantly beds of 

 amphibolite ; on the other hand, green micaceous and calcareous 

 strata are common to the Scipsius schists and to the micaceous Ursern 

 gneiss near its boundary with the Gothard massif. 



In the summary profile I have made an attempt to parallel these 

 groups of crystalline schists with the previous classifications of 

 Favre, von Hauer, and Oastaldi, without being convinced that such 

 a parallelization is practicable in detail; and a further attempt to 

 fit these different ci-ystalline schists into the frame of the American 

 classification of the Archsean, I now recognize to be a mistake, since 

 the Gothard rocks, from I. upwards, are decidedly younger than 

 Archajan. 



5. The rocks belonging to the fifth series, viz. gray and green 

 mica schists, with or without garnets and disthene, sericite schists, 

 black" schists, calc schists, dolomites, cipoline, marble, rauchwacke, 

 have been characterized in § I.-III., where it is pointed out that they 

 extend from the Carboniferous to the Jurassic age. They occupy 

 the trough of the Ticino on the south side, and on the north side that 

 of the Ursern (pis. v.-vii. and iii.-iv. of the map ; summary profile 

 on title sheet) ; but they are represented also north of the Gothard, 



