74 
SCENERY OF SWITZERLAND. 
dition,” says Escher, “vary not only in different 
layers, but even in different parts of the same layer, 
so that we often pass from one extreme to the other 
by imperceptible gradations.” 
Grubenmann,* who has recently published a 
special memoir on the Granites of the St. Gotthard, 
points out that they may all have been derived from 
an originally similar rock, modified by differences of 
pressure and temperature. Schmidt suggests that 
we find normal Granites in just those parts of the 
central massives where we should expect the pres- 
sure to be less extreme, while Protogine occurs 
in the more intensely folded parts. Duparc and 
Mrazec,** who have especially studied the Protogine 
of the Mont Blanc Massif, regard it as a granulitic 
Granite. 
Heim has pointed out that many rocks which 
m hand specimens might well be taken for Granite 
are shown to be really stratified if seen in larger 
masses. As already mentioned, he regards some 
varieties of Gneiss as part of the original Earth’s 
crust. He regards parts of the Protogine as com- 
pressed Granite, and some ot the Gneiss as com- 
pressed Protogine; while other Gneiss masses he 
* Verh. Turgaisch. Nat. Ges. 1890. 
j^rch. Sc. Phys. et Nat. de Geneve, 1892. 
