SO-CALLED ' GjJfEISS ' OF OARBONIPEEOFS AGE AT GUTTANI!fEN. 3d?i 



size by blasting. The slabs now in the Berne Museum were ob- 

 tained from the first and bigger block. 



"We decided to examine a continuous section of the belt of the 

 ' Carboniferous gneiss/ and selected, after some reconnoitring, the 

 eastern side of the valley.^ We did not, however, entirely neglect the 

 western side, for we studied many of the erratics in the ' scatter ' 

 from it below Guttannen, and the rock itself in crags which rise 

 from the bed of the valley some distance above the village. 



We crossed the Aar and followed its course till we reached the 

 indubitable gneiss : then, mounting to a height of some three or 

 four hundred feet above the river, we worked back, scrambling up 

 and down the grassy slopes so as to touch as many outcrops of rock 

 as was possible Avithout greatly altering our level. 



Commencing at a waterfall which plunges over rock into a ravine 

 descending in a S.W. direction, we found on the right bank of the 

 latter the normal gneiss, on the left the ' Carboniferous gneiss.' * 

 But on the former rock a marked cleavage-foliation has been 

 impressed so as to make it quite slaty ; in the latter also there 

 is a rough cleavage — so that ia the field the exact line of demarcation 

 cannot easily be determined. After a time indubitable ' cleaved ' 

 gneiss is again struck,^ on the right bank of a little stream which 

 joins the Aar about two furlongs below Guttannen. This can be 

 followed for some distance on the other side. The bosses of ice- 

 worn rock, however, which project from the slopes jS'.E. of 

 Guttannen and some 450 feet above it, consist of 'Carboniferous 

 gneiss.' But it is doubtful whether the latter extends far ; for the 

 rock exposed in some other outcrops a little distance onwards bears 

 more resemblance to crushed normal gneiss ; and this certainly seems 

 to occur about due E. of Guttannen. We traced the last-named 

 rock down to the neighbourhood of a pathway which leads into that 

 village by a bridge over the Aar. Here it consists of alternating 

 bands of quartzo-felspathic and of more micaceous rock — the former 

 rather more than a quarter of an inch in thickness, the latter about- 

 one inch ; a common type in the gneiss of the valley below Guttannen, 

 though here much contorted. But at a distance of a few yards, close 

 by the path, we again found the ' Carboniferous gneiss,' in which 

 are spots of a white mineral, rather smaller than a pea, suggestive of 

 a fragmental structure. Beyond this place, though we passed many 

 erratics and crossed a slope of debris (avalanche), we were not so 

 fortunate as to discover any more of the ' Carboniferous gneiss' in situ, 

 so long as we were on open ground. But on entering the forest we 

 felt doubtful whether one or two crags which we found near the 

 margin might not be this rock. Coarse gneiss, however, soon sets 



^ It is needless to enter into the reasons for our choice, as they eouki be 

 iindei'stood only by those who have a minute knowledge of the ground. I 

 was accompanied and aided in tbe fiekl work by Mr. Jas. Eccles, F.G.S., to 

 whom I tender my best thanks for invahiable assistance then and since. 



- It will be convenient to use this term to indicate the rock of clastic origin 

 which is the subject of this paper, though, as will be understood, I maintain 

 that it is improperly designated a ' gneiss.' 



^ At the base of a wood near the chalets of Vorsaas. 



