138 
Then followed a third period of extensive denudation, and the 
Cretaceous rocks were laid down, to be, in their turn, denuded 
away in late Tertiary times. 
Finally came the great period of elevation, when the mountain 
masses were slowly brought up to a position higher above the sea 
than they have at present. ‘Then it was that thermal springs, 
connected with the waning volcanic action of the period, carried 
up the minerals that now fill the metalliferous veins. In connection 
with these, limestones, as in the case of the hematite deposits, 
play a most important part. 
Later still came the great Glacial episode, which resulted in the 
removal of enormous quantities of rock from the areas under 
notice, and which, in doing so, shaped the limestones of the district 
into surface forms quite different from what they would have taken 
under ordinary atmospheric denudation. 
Then, later, subaerial denudation reasserted its sway upon the 
limestones, and is etching and wearing them into something like 
their preglacial forms. 
