Vol. 50.] CRYSTALLINE SCHISTS IN THE LEPONTINE ALPS. 299 



seen the garnets in this rock distinctly red and the silvery mica 

 exceptionally dominant. I postpone any further inferences from 

 this Val Canaria section till I have described another district. 



IV. Section South of the Val Bedretto. 



The schists, of which the northern face of the range on the side 

 of this valley, nearly as far as Faido, is composed, are mapped by 

 Von Fritsch as part of the mass to which those of the Val Piora 

 belong. In order to compare the two I went from Rodi Fiesso 

 (3110 feet) to the neighbourhood of the Campolungo Pass (lying, 

 roughly, S.S.E. of the lower end of the Lago di Ritom). From a 

 short distance above that village the path, which ascends steeply to 

 the Lago di Tremorgio (5997 feet), traverses schists like those of 

 the Pian Alto, 1 having streaky bands of dark mica, with brownish, 

 more quartzose seams and yellowish streaks of calcite or crystalline 

 calcareous rock. After passing the lake, the path, which mounts 

 the steep slopes on its right bank, crosses similar rocks ; but I found 

 fallen blocks of black-garnet schist and one or two small outcrops 

 of it in situ : for instance, at about 700 feet above the level of the 

 lake. At the top of these slopes (about 160 feet higher) we come 

 to the ' Campolungo,' a grassy plain or hollow excavated in a mass 

 of white dolomite. At its western end, below the actual Campo- 

 lungo Pass (7595 feet), the dolomite exhibits a fold, extraordinary 

 even for the Alps. As it crops out from the turf it assumes this 

 shape — CTT? — being flanked by the dark schists on the south and 

 partly overlain by them on the north. But at the eastern end of 

 the hollow, where the path to Faido (which I followed) crosses a 

 high spur from the main range, the dolomite appears to be regularly 

 interbedded with the schists. 2 North of the pass (7041 feet) 

 (nameless on the map) the schist seems to rise from beneath the 

 dolomite and forms a ridge in which the rocks obviously correspond 

 with those traversed by the path below, in ascending from the Lago 

 di Tremorgio ; the culminating point on this ridge is about 400 feet 

 higher than the pass. On the south side of the latter the dolomite 

 becomes flaggy and micaceous for about a dozen or 14 feet, and 

 then changes rather suddenly into a mass of schists which bear a 

 general resemblance to the ordinary dark-mica schists of the Val 

 Piora, and contain some seams of typical black-garnet schist. This 

 ' dolomite ' consists of a well-bedded group of strata, which vary 

 slightly in character and probably in composition. Sometimes they 

 are pure white, sometimes greyish, sometimes yellowish. Tremolite 

 is often abundant, the crystals not seldom being over 2 inches in 

 length, and fine masses can be readily picked up. The mineral 

 appears to occur in rather irregular lenticular seams. I have 

 recorded in my notebook full details of the section from the one 



1 Op. cit. pp. 199-203. 



2 The simplest explanation is that the flat curve of the dolomite becomes 

 more pointed towards the east and is pushed over to the north, so the beds on 

 this side (apparently below) are part of the mass which overlies it on the south. 



