ZURICH AND GLARUS. 
185 
ancient, and has taken no active part in this remark- 
able overthrust. It has been perfectly passive, being 
itself folded with the other strata. The whole region 
is particularly instructive. 
At the commencement of the Carboniferous 
period the older sediments, converted more or less 
into Crystalline Schists, contained already intruded 
masses of Granite, and were thrown into folds, form- 
ing a mountain chain. Over these sediments a mass 
of porphyritic lava was poured from some volcano or 
volcanoes, the site of which has not yet been dis- 
covered; and this lava was subsequently covered by 
another series of Carboniferous deposits. Before the 
Permian another period of folding occurred, and the 
folds were partly denuded, during a long period of 
subsidence, in which no less than 500 metres of 
calcareous sediment was deposited. The porphyry, 
which now occupies the summit of the Windgalle at 
a height of 3000 metres, was then covered under a 
great thickness of Jurassic and Eocene strata. Finally 
came the foldings which have given rise to the pre- 
sent mountains, in which all the strata from the 
Carboniferous to the Eocene are folded conformably 
together. 
