222 
The Great Ice Age and Origin of the “Till.” [April, 
without the formation of crevasses, according to the thick- 
ness of the ice and the degree of curvature. 
A glacier reaching the sea by a very steep incline would 
probably break off, in accordance with Mr. Geikie’s descrip- 
tion, just as an Alpine glacier is ruptured fairly across when it 
makes a cascade over a suddenly precipitous bend of its 
path. One entering the sea at an inclination somewhat 
less precipitous than the minor limit of the effective rupture 
gradient it would be crevassed in a contrary manner to the 
crevassing of Alpine glaciers. Its crevasses would gape 
downwards instead of upwards — have an A-shaped instead 
of a V-shaped section. 
With a still more moderate slope, the up-floating of the 
termination of the glacier, and a concurrent general up- 
lifting or upbending of the submerged portion of the glacier 
might occur without even a partial rupture or crevasse 
formation occurring. 
Let us now follow out some of the necessary results of 
these conditions of glacier existence or glacial prolongation. 
The first and most notable, by its contrast with ordinary 
glaciers, is the absence of lateral, medial, or terminal 
moraines. The larger masses of debris, the chippings that 
may have fallen from the exposed escarpments of the 
mountains upon the surface of the upper regions of the 
glacier, instead of remaining on the surface of the ice and 
standing above its general level by protecting to some 
extent the ice on which they rest from the general snow- 
thaw, would become buried by the upward accretion of the 
ice due to the unthawed stratum of each year’s snow-fall. 
The only thinning agency at work upon such glaciers 
during their journey over the terra firma being the outflow 
of terrestrial heat, and that due to their fridtion upon their 
beds, the thinning must all take place from below, and thus, 
as the glacier proceeds downwards, these rock fragments 
must be continually approaching the bottom instead of con- 
tinually approaching the top, as in the case of modern 
Alpine glaciers flowing below the snow-line. 
An important consequence of this must be that the erosive 
power of these ancient glaciers was, cceteris paribus, greater 
than that of modern Alpine glaciers, especially if we accept 
those theories which ascribe an adtual internal growth or 
regeneration of glaciers by the relegation below of some of 
the water resulting from the surface-thaw. 
It follows, therefore, that such glaciers could not deposit 
any moraines such as are in course of deposition by existing 
Alpine and Scandinavian glaciers. 
