CONTINENTAL ICE OF GREENLAND. 
171 
from the icy slope, and a few superficial lines of stones or 
moraines are visible at certain seasons, when no snow has 
fallen for many months, and when evaporation, promoted by 
the wind and sun, has caused much of the upper snow to 
disappear. The height of this continent is unknown, but it 
must be very great, as the most elevated lands of the out¬ 
skirts, which are described as comparatively low, attain alti¬ 
tudes of 4000 to 6000 feet. The icy slope gradually lowers 
itself towards the outskirts, and then terminates abruptly in 
a mass about 2000 feet in thickness, the great discharge of 
ice taking place through certain large friths, which, at their 
upper ends, are usually about four miles across. Down 
these friths the ice is protruded in huge masses, several miles 
wide, which continue their course—grating along the rocky 
bottom like ordinary glaciers long after they have reached 
the salt water. . When at last they arrive at parts of Baffin’s 
Bay deep enough to buoy up icebergs from 1000 to 1500 
feet in vertical thickness, broken masses of them float otif, 
carrying with them on their surface not only fine mud and 
sand but large stones. These fragments of rock are often 
polished and scored on one or more sides, and as the ice 
melts, they drop down to the bottom of the sea, where large 
quantities of mud are deposited, and this muddy bottom is 
inhabited by many mollusca. 
Although the direction of the ice-streams in Greenland 
may coincide in the main with that which separate glaciers 
v/ould take if there were no more ice than there is now in the 
Swiss Alps, yet the striation of the surface of the rocks on 
an ice-clad continent would, on the whole, vary considerably 
in its minor details from that which would be imprinted on 
rocks constituting a region of separate glaciers. For where 
there is a universal covering of ice there will be a general 
outward movement from the higher and more central re¬ 
gions towards the circumference and lower country, and this 
movement will be, to a certain extent, independent of the 
minor inequalities of hill and valley, when these are all re¬ 
duced to one level by the snow. The moving ice may some¬ 
times cross even at right angles deep narrow ravines, or the 
crests of buried ridges, on which last it may afterwards seem 
strange to detect glacial striae and polishing after the lique¬ 
faction of the snow and ice has taken place. 
Rink mentions that in North Greenland powerful springs 
of clayey water escape in winter from under the ice, where 
it descends to “the outskirts,” and where, as already stated, 
it is often 2000 feet thick—a fact showing how much grind¬ 
ing action is going on upon the surface of the subjacent 
