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 

 "^-rr^^y^^^^^^^ greater tribu- 



ne. 71. HANGING VALLEY, FRAZER REACH. tSLTV 



Ice-rounded summits in the distance. -i , i 



approach the 



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- 



