268 
SCENERY OF SWITZERLAND. 
acid, acts on Granite profoundly. In many quarries 
where it looks solid enough it will be found to be 
disintegrated to a considerable depth, and even 
changed into a loose sand. This is due to the 
l'elspar; the alkaline salts of Soda and Potash being 
decomposed by the carbonic acid, leaving the Silicate 
of Aluminium, the Mica, and the Quartz. It seems 
at first inconsistent with this that Granite ridges are 
often peculiarly jagged, but in such cases the Granite 
is steeply inclined, and the debris are removed as 
they form. 
In othei cases Granite shows a tendency to weather 
in convex, but somewhat flat shells, and to split verti- 
cally in two or often three different directions: it is 
divided, moreover, into horizontal layers at more or 
less regular intervals, thus forming rhomboidal blocks 
or pillars. Granite possessing this structure often as- 
sumes very bold, wild forms. 
Protogine, though so similar to granite, generally 
gives a different scenery. It breaks up more readily 
into Aiguilles, and the divisional plains are more 
marked. The vertically constructed Protogine of 
the Mont Blanc range, for instance, has a different 
aspect from the chains which are composed of true 
granite. 
The “Aiguilles” formed by Crystalline Schists, 
