58 Professor T. G. Bonney [April 4, 



I shall again ask permission to conduct you to a series of typical 

 sections, which, however, I shall describe with less minuteness. 



Let us place ourselves in imagination on the great ice-j6.eld at the 

 upper part of the Gross Aletsch Glacier — the Place de la Concorde of 

 Nature, as it has been happily termed. We are almost hemmed in by 

 some of the loftiest peaks of the Bernese Oberland : the Aletschhorn, 

 the Jungfrau, the Monch, and several others. We find the rocks 

 which rise immediately round the glacier — as, for example, near the 

 well-known Concordia hut — to be coarse gneisses, with difficulty dis- 

 tinguishable from granites. As the eye travels up any one of the 

 mountain ridges, the rock evidently becomes less massive and more dis- 

 tinctly foliated. We note the same sequence as we retrace our steps 

 towards the Ehone valley — speaking in general terms, the ridges and 

 the flanks of the Eggischhorn consist of more finely granulated 

 gneisses and of strong micaceous schists, which alternate more fre- 

 quently one with another. Further to the west, in the region around 

 the Oberaletsch Glacier and on the slopes of the Bell Alp, we find the 

 same succession — coarse granitoid gneisses in the relatively lower part 

 of the heart of the chain, finer grained and more variable gneisses and 

 schists on the upper ridges and the southern flanks. 



Let us change our position to a spot considerably to the east, to 

 the great section of the crystalline series made by the valley of the 

 Keuss below Andermatt. 



From the spot where the rocks close in suddenly upon the torrent 

 near the Devil's Bridge, to a considerable distance below Wasen, ex- 

 tends an almost unbroken mass of coarse granitoid gneiss. This, how- 

 ever, becomes more distinctly bedded and schistose before it entirely 

 disappears beneath the secondary deposits that border the Bay of Uri. 

 Similarly, if from Wasen, where the gneiss is barely distinguishable 

 from granite, we ascend the wild glen which leads up to the Susten 

 Pass, and descend on the other side by the grand scenery of the Stein 

 Alp to the beautiful Gadmenthal, thus passing obliquely outwards 

 along the apparent strike of the rocks to the point where, as in the 

 neighbourhood of Imhof, they finally disappear beneath mesozoic 

 deposits, we again find that we are among rocks which are rather 

 more variable in their mineral character, oscillating between 

 moderately coarse gneisses, sometimes porphyritic, and strong mica 

 schists. Near Miihlestalden, in the Gadinenthal, even a bed of white 

 crystalline dolomitic limestone is interstratified with the gneissic 

 rocks. 



Leaving for a brief space the vicinity of the St. Gothard road, and 

 returning to the upper valley of the Ehone, let us place ourselves on 

 such an outlook as we can obtain from Professor Tyndall's chalet on 

 the Bel Alp, and fix our eyes on the magnificent panorama of the 

 Pennine chain, with whose geology we will suppose ourselves to 

 have become familiar in frequent traverses from the northern to the 

 southern side of the watershed of Central Europe. Facing us, and 

 forming the lower slopes and crags of the great mountain chain 



