GLACIATION IN THE ATLIN DISTRICT 185 
a few feet higher than the level of the lake, and a mile or so 
back from it. The intervening valley is flatly floored with 
quicksand or gravel, and is at times a mile wide at the ice front. 
A rather small collection of morainic dumps lies in front of 
the ice. Swift glacial streams issue from beneath the ice front 
over beds of quicksand or gravel. These are heavily charged 
with sand and silt, but do not appear to bring out coarser 
material. These streams remove much of the coarse medial 
morainic material as it is gradually dumped over the ice front, 
and this may account for the small terminal moraines. 
These medial moraines form wide low ridges of unassorted 
rock matter, stretching far back into the ice field, until they are 
lost to sight on the skyline or beneath fresh fallen snow. 
The ice front rises very gradually backwards into the nearly 
level field of ice and snow, which continue south and westwards 
to Taku Inlet and the Pacific coast, a distance of 60 miles. 
The upper surface of this ice field is about 5,000 feet above 
sea level, or 3,000 feet above Atlin Lake. Out of the general 
level of this inclined plain, mountain groups and peaks project, 
leaving wide, level gaps between them. Near the ice fronts the 
glacial surface is traversed by many small streams, which soon 
fall into crevasses. These probably supply most of the water 
which issues from the glacier front. Water action must be very 
slight within the interior region of the main glacier. 
It appears that any loose material formed on the projecting 
mountain sides above the glacier will be removed. Frost and 
snow slides are very active agents in breaking up rock masses. 
The broken material finds no angle of rest. It falls between the 
ice and the shore and becomes a grinding agent, or else is borne 
out to feed the great medial moraines, hence it seems that this 
glacial action is very largely a widening one, continually trim- 
ming the sides of its directing walls, and acting as a carrier. 
In such a way it may have widened out the water-worn 
troughs of the preglacial drainage, leaving at times portions 
of the deep stream bed unremoved. 
JG. Gwitrim, 
NELSON, BRITISH COLUMBIA. 
