H4 
ALASKA GLACIERS 
200 to more than 1,000 feet. The immediate walls are 
1,000 to 2,000 feet high, curving back to rounded sum¬ 
mits. On the mainland side the fiord is joined by many 
troughs of similar depth and character, and by a few 
hanging valleys. From Vancouver Island it is joined by 
many hanging valleys. The sills of the hanging valleys 
best seen lie from 200 to 500 feet above tide and are evi¬ 
dently carved from the rock. Below each sill the con¬ 
tours of the main trough are continuous, without any de¬ 
flection toward the side valley, and the draining stream has 
only begun the work of grading its channel. A shallow 
trench is cut on the edge of the sill, and escaping from 
this, the water tumbles down the open face of the fiord 
wall. Other valleys hang so high that from our low point 
of view we could not look into them. At a moderate 
estimate the highest seen are 1,000 feet above the water, 
and as these occur opposite the deeper part of the chan¬ 
nel it is probable that the maximum discordance of valley 
floors is not less than 2,000 feet. All the hanging valleys 
appeared to be steep-sided glacial troughs, and those we 
saw best are at least several miles in length, with moun¬ 
tains behind them. 
For this complicated system of troughs I have not been 
able to suggest an origin that does not involve an immense 
amount of excavation by ice. The hypothesis demanding 
least of the ice is one which assumes the main fiord to 
follow a belt of weak rock, in which pre-glacial streams 
had sunk their beds rapidly, outstripping such small trib¬ 
utaries as had strong rocks to contend with. Under 
such conditions, all pre-glacial valleys, with the possible 
exception of those in the weak rock, would have been 
narrow gorges, and the work of the ice in enlarging them 
to existing dimensions would be at least as great as the 
preceding work of the streams. While this work was be¬ 
ing done by the tributary glaciers, the trunk glacier may 
