146 
ALASKA GLACIERS 
The thorough rounding of crests on Vancouver Island 
extends so far above the floors of the observed hanging 
valleys as to indicate that their glaciers were not features 
of the stage of maximum glaciation. It is quite possible 
that the greatest flood from the mainland turned back the 
feebler streams originating on the island and sent currents, 
here and there, through mountain passes to the southwest¬ 
ern coast. 
Along the narrow passages separating Princess Royal 
and Pitt islands from the mainland, hanging valleys are 
equally abun¬ 
dant, and the 
illustrations of 
the physio¬ 
graphic type 
are even more 
striking. The 
greater tribu¬ 
tary valleys 
approach the 
FIG. 71. HANGING VALLEY, FRAZER REACH. 
Ice-rounded summits in the distance. 
fiords from the mainland and have sills near water-level, 
some of them lying so low as to contain shallow bays. 
All of the sills on the side of the islands are above tide, 
and the valleys back of them are surprisingly broad when 
considered as the channels of glaciers originating on is¬ 
lands only fifteen to twenty miles wide. The change of 
grade from the floor of the hanging valley to the side 
wall of the main valley is so abrupt as to give the impres¬ 
sion that the sill is really a parapet, and that the alcove in 
the fiord wall contains a basin. At one point (fig. 70) 
we climbed to a sill with the half expectation of discover¬ 
ing a lake beyond, but found only the uneven, and in 
places marshy, floor of an ordinary U-trough. The high¬ 
est sills seen are about 1,000 feet above tide. 
As Grenville Channel, the passage separating Pitt Is- 
