8 Dr. F. M. Stapff— Crystalline Schists 



1833 ra. inside the mountain, counted from the mouth of the tunnel " 

 {he. cit. French text, p. 66; German, p. 51, 52). Describing the 

 glacial and alluvial gravels in the Ticino valley (" Geologische 

 Beobachtungen im Tessinthal, wiihrend Traciruna: und Baues der 

 Gotthardbahn," Berlin, 1883), I have likewise pointed out the 

 difference between the ordinary black garnet schists and the Nufenen 

 * spotty ' schists: whilst the former are spread far down the valley, 

 the Nufenen ' spotty ' schists were not met with beyond five or six 

 kil. below the pass {loc. cit. p. 83). 



The fact is, that schists and slates which are coloured by graphite 

 or other coaly material, sometimes phyllitic, sometimes calciferous, 

 and often garnet-bearing, occur on the Gothard under various con- 

 ditions, and in widely separated geological horizons. On his map 

 of the Gothard district, von Fritsch indicated by the colouration of 

 the Nufenen schist, a patch of black garnet schist in the upper part 

 of the TJnteralpthal. On examination I found it to be a slender 

 intercalation in the micaceous gneiss of the Sorescia type, which, 

 on the summary profile to my geological map of the Gothai'd 

 railway, is designated by III., and which has been cut by the tunnel 

 between 3000 and 4000 ra. from the southern entrance. This 

 occurrence of black garnet schist in the brown micaceous gneiss 

 III. is not an isolated one. I have mapped a quite analogous 

 instance in the upper Val Cadlimo, close by the Lago Scuro. 



On a higher horizon, we meet with the black schists (without 

 macroscopic garnets) of the Oberalp road, which were exposed in 

 the tunnel between 3650 and 3800 m. N. ; probably they are of 

 Carboniferous age and equivalent to the black garnet schists on the 

 south side, at 1466 and 1808-1833 m.> 



Some seams of black schist were met with in the tunnel at 3263 

 and 3274 m. N., between the Altkirche schists and the above- 

 mentioned Oberalp schists, which have not been traced at the 

 surface ; they probably correspond with the black garnet schists on 

 the south side at 700-800 m. The bed-rocks are calcareous on 

 both sides of the mountain ; I consider them to be of Triassic age, 

 as well as the bulk of the calc-mica schists on the opposite side of 

 the Ticino river, which also inclose several belts ot black garnet 

 schists, one, for example, in the Stalvedro railway tunnel. 



Finally we arrive at the highest horizon of black schists, viz., 

 those of Altkirche on the north side, met with in the tunnel at 

 2582, 2637, 2766 m. N., which I consider to be of Liassic age and 

 to correspond with the Nufenen belemnite schists. These have not 

 been seen in the southern section of the tunnel, though it is possible 

 that the}'- may be represented there by some geological equivalent. 



These different black schists do not completely agree in their petro- 

 graphic characters, not even if comparison is made with those which 



^ These and other intercahitions of special geological interest have been purposely 

 very prominently marked on the profll geologique in order to attract attention to 

 them. For exact measures and details refer to my record: " Geologische Tabellen 

 und Durchschnitte, iiber den grossen Gotthardtunnel ; Specialbeilage zu deu 

 I3erichteu des Schweizerischen Bundesrathes iiber den Gang der Gotthardbahn- 

 unternehmung, 1873-1882." 



