172 CONVERSION OF VALLEYS INTO LAKES. [Ch. XII. 



unequal movements of upheaval and subsidence. I assumed that the 

 Alpine region had been exposed for countless ages to the action of rain 

 and rivers from Older Pliocene if not from Upper Miocene times, and I 

 therefore inferred that the larger valleys, throughout the greater part 

 of their depth and width, were of pre-glacial origin. If they were 

 not so, it seemed to me that we should be called upon to explain a more 

 difficult enigma than the origin of the lake-basins, namely, why the 

 rivers had been idle for a million years or more, leaving to glaciers the 

 task of doing in comparatively modern times the whole work of ex- 

 cavation. 



The Alps are from 80 to 100 miles across. Let us suppose a cen- 

 tral depression in this chain at the rate of 5 feet in a century, while the 

 intensity of the movement gradually diminishes as it approaches the 

 outskirts of the chain, till at length it dies out in the surrounding 

 lower region. After a long continuance of such a change of level, 

 there will not only be a lessened fall of all the rivers, but the courses 

 of many of them will, at various points, especially near the foot of the 

 mountains, be converted into lakes. If, in the case of Wales, we can 

 demonstrate an upward movement of 1400 feet during a part of the 

 glacial epoch, we may well suppose still greater alterations of level in 

 the Alps, and agree with Charpentier that those mountains which from 

 a remote geological era have been the theatre of reiterated upward 

 and downward movements may have been, at the time of the most in- 

 tense cold, three thousand feet higher than they are now. They may 

 also have been lowered again, as I have elsewhere suggested (" Anti- 

 quity, of Man," p. 321,) before the close of the Glacial epoch, and 

 oscillations of such magnitude may well have been accompanied by 

 such inequalities of movement as would inevitably have turned some 

 parts of the preexisting valleys into the receptacles of vast bodies of 

 ice, destined afterward to be converted into water. We know that 

 in the earthquake in the northern island of New Zealand, in January, 

 1855, there was a permanent rise of land on the northern shores of 

 Cook's Strait to the extent of 9 feet vertically. On one side of Muko- 

 muka Point, or immediately to the east, there was no movement, 

 while on the other side, or to the westward, there was a gradual dimi- 

 nution of the upheaval from 9 feet to a few inches, until, at a distance 

 of about 23 miles, no change of level was perceptible. Simultaneous- 

 ly with this elevation of land, there was a sinking of the low coast to 

 the amount of 5 feet in the middle island south of Cook's Strait, 

 The repetition of such unequal movements may, in a time geologically 

 brief, turn parts of any valley into a lake. In Finmark an ancient 

 water-level has been carefully measured along the borders of a fiord, 

 rising gradually at the rate of 4 feet in a mile for 30 miles from south 

 to north, until at one extremity it attains an elevation of 135 feet 

 above the other end, and this movement is of post-pliocene date. 

 Whenever the lower part of a fiord or valley is thus raised, or when- 

 ever in the upper portion, subsidence is in like manner in excess, 9 



