MECHANICAL ACTION OF GLACIERS. 153 
small white cloud in the zenith, a few acres in extent, in 
violent internal agitation (from the hurricanes of wind 
blowing through it), yet immovable as if fixed by some 
spell, the material ever changing, the form and aspect 
unvarying. The “Table-Cloth” is formed also at the com- 
mencement of a “north-wester,” but its fringes then 
descend on the opposite side of the mountain, which is no 
less precipitous,’ 
Other illustrations, perhaps more pertinent, are supplied 
by sand ripples on the shore, and by the contour of sand 
drifts, while an illustration of reboundings out at sea, like 
to the erial rebound described in the passage cited from 
the writings of Sir John Herschel, are supplied by banks 
in some of the Argyleshire lochs, vertical to the line of 
descent of the Highland glen down which in pre-Adamic 
times poured the glacier which hollowed out the basin. 
The confining sides of a valley once formed would elongate 
the furrow or depression thus created in a direct rather 
than a cross direction; but the alternate elevations and 
depressions, and thus the succession of pits in the thalweg 
of the glacier, may also have been thus produced. 
In view of this it becomes more easy to see how 
pools of such depths of water as 780 feet, 840 feet, 1,584 
feet, 2,964 feet, 3,766 feet, and 3,980 feet, may have been 
produced in the Sogne fiord and its branches, while the 
depth of the sea at the mouth of the fiord is only 600 feet, 
may have been produced, and successions of such hollows 
in the line of the fiord and lateral branches. In alike way 
may have been produced the basins of such lakes in the 
interior of the country as the Miosen with a depth of 
basin 1,110 feet below the level of the sea, corresponding 
to the depth of the sea basin in the outer portion of the 
Christiania fiord. 
The force with which the water of such falls as have 
been described impinge on the basin at their base must be 
tremendous; but water is a liquid yielding material. 
Imagine what must have been the impinging force of an 
