CENTRAL MASSIVES. 
The Granite is no doubt for the most part of 
great antiquity, pebbles of it occurring in Car- 
boniferous Puddingstone; it crops up in many places, 
now more or less detached, and there were probably 
several distinct eruptions of this rock; but the action 
of subsequent denudation has divided many tracts 
which unquestionably were once continuous. Some 
Granite is no doubt inU'usive. This is shown by the 
fact that the rocks near it are in many places forced 
up and modified by heat. Still it would be a mis- 
take to regard the Granite as having been the active 
agent of disturbance; it was, on the contrary, itself 
forced up by the general side pressure. In some 
cases it appears not to have entirely broken through 
the overlying rocks, but is exposed in deep ra- 
vines.* 
I have already shown that the Central Massives 
were once covered by a great thickness of Secondary 
rocks. Apart from this evidence, however, Ve must 
bear in mind that Gneiss, Granite, and Crystalline 
Schists must have cooled under great pressure and 
at a great depth. When we stand on such a rock 
we must in imagination replace over it several thou- 
sand feet of rock now removed. Gneiss would as it 
approached the surface gradually have assumed a 
* Theobald, Beitr, z. GeoL K> d. Schw,^ L. III. 
Scenery of Switzerland. II. ^ 
