28 GEOLOGICAL MEMOIRS. 



gneiss. M. Studer is of opinion that the hypothesis of erosion by 

 glacier-ice, propounded by Agassiz and his followers, is the most 

 simple and the most in accordance with nature. 



The mass of St. Gothard approaches nearer to that of the Finster- 

 aarhorn on the south than the Mont Blanc group to the Aiguilles 

 Rouges. It is far from being so considerable in linear extension as 

 the group of the Finsteraarhorn, though more so than the Mont Blanc 

 group, which last however is broader and loftier. Immediately 

 above the Hospital are well-marked mica-slates ; and above, towards 

 the Gemsboden, distinct gneiss. The region of the granite proper of 

 St. Gothard begins at the level of the Gothard lakes. On the south- 

 ern declivity towards Val Treniola, gneiss again occurs, followed by 

 hornblende rock and dolomite. The well-known fan-shaped structure 

 of St. Gothard extends as far east as the granite can be traced. 



This locality is celebrated for the variety of its minerals. Daubree 

 has justly observed, that there is a remarkable resemblance between 

 the substances found in the " central masses " of the Oisans, of 

 Mont Blanc, the Finsteraarhorn, and St. Gothard, so as to give 

 independent support to the view of these mountains having a very 

 close internal relation. There are moreover analogies between many 

 of those mineral substances and the products of existing volcanos, 

 which, from the great difference between the rocks containing them, 

 could not have been anticipated. From such comparisons the 

 chemist draws conclusions, which it is to be hoped will throw light 

 upon the obscure origin of these nuclei. New investigations, 

 however, and comparisons of the different localities, their geological 

 relations, and the condition of the matrix, will probably be needed 

 for the safer foundation of such speculations ; and on this point we 

 may shortly expect valuable information from M. Wiser of Zurich, 

 who has done so much for the study of Swiss mineralogy. 



The " central mass " of the Alps of the Valais appears to be a pass- 

 age from the lofty fan-shaped rocks lying next to the exterior chain 

 and the gneiss formation of greater horizontal extension forming the 

 inner range. A fan-like structure is not clearly shown in the gneiss 

 and mica-slate, and a disposition to symmetric arrangement is want- 

 ing. Beds of limestone and marble are more abundant ; serpentine 

 and gabbro pierce through them ; and on the southern side of the 

 group occurs a syenitic granite, such as is seldom seen but on the 

 southern margin of the chain. The characteristic of this central 

 mass is the intimate relation of its rocks with those of the schistose 

 zone which flanks it, arising from both having undergone the same 

 flexure and from the mineralogical passage of the one rock into the 

 other. 



Talcose gneiss and green slates together with serpentine and gabbro 

 form all the mountains on both sides of the Ferpecle glacier and the 

 Col d'Erin. In the principal mass of that remarkable and inac- 

 cessible mountain, the Mont Cervin, the formations are distinctly 

 divided by their colour, as at the Aiguilles Rouges. In many 

 parts of these mountains, and notably on the heights of the Matter- 

 jochs, may be seen most complicated relations between gneiss, serpen- 



