260 THE FOREST LANDS OF FINLAND. 
of the water having been much greater formerly than it is 
now; and greater depth in such cases implies greater velo- 
city ; and greater velocity implies greater power. From 
what the flow now is, carrying off only the drainage of the 
rainfall in the higher lying basin, we may imagine what it 
must have been, when it was carrying off the meltings under 
an elevated temperature of glaciers formed of the accu- 
mulated snows of the glacial period. 
Marine engineers employed in the construction of break- 
waters and like undertakings have made us acquainted 
with the fact of stones tons in weight betng displaced and 
tossed about by the waves during a storm. Here such 
masses must have been moved by the river’s flow; and 
from this we may again imagine what must have been 
the mass of waters pouring down from the melting 
glaciers, and this not by a steady, constant flow, but alter- 
nating with this at times another phenomenon of glacial 
action, 
There is a phenomenon well known in Alpine regions : 
the débdcle, or outburst of water resulting from the melting 
of snow pent up in some secondary valley, to which free 
passage has been suddenly given by the melting of the 
icy barrier. A characteristic example is one furnished by 
the glacier of Giétroz. 
At the bottom of the valley of Bagnes, one of the 
-branches of the Drause, at sixteen kilometres, or about 
twelve miles from Chadles, there rises vertically a high 
wall of rocks surmounted by the glacier of Gidtroz. The 
moving mass protrudes itself, projects beyond the support, 
and falls at the foot of the precipice ; the broken fragments 
congeal anew and form a cone-shaped glacier, which pushes 
before it its moraines. What ensues must be given in 
the narrative of Guide Joanne :—‘In those years in which 
avalanches are very frequent the heat of summer does not 
suffice to melt a quantity of ice equal to what the moun- 
tains cast down. The enormous block which then forms 
a bridge on the Drause becomes always larger and larger, 
