OSIER ISLAND 69 



ness. The central part of the Turner ice cliff in 1899 was 

 250 feet high, but as the surface of the glacier was greatly 

 dissected by crevasses its average height above water was 

 somewhat less and may be roughly estimated at 220 feet. 

 This would give for the total thickness 1,760 feet, and for 

 the submerged portion 1,540 feet. The theory that the 

 glacier floats, thus implies that the bay has a depth close 

 to the northwest shore of 1,600 feet, and the central depth 

 should be considerably greater. The theory could there- 

 fore be tested by sounding. 



Osier Island. The little island at the turn from Dis- 

 enchantment Bay to Russell Fiord (see pi. vin) is a low 

 knoll constituted of the altered shales of the Yakutat for- 

 mation. A rocky reef extends northwest from it, and a 

 gravel spit, bare at low tide, joins it to the mainland. It 

 has three faces, characterized by cliffs telling of active 

 erosion by waves. The east face is turned toward Rus- 

 sell Fiord and receives the waves generated by southerly 

 and southeasterly winds in a straight stretch of deep 

 water nineteen miles long and from one and a half to two 

 miles broad. A high cliff testifies to their efficiency, and 

 so does the gravel spit just mentioned, to which they have 

 brought not only pebbles but large boulders. The north 

 face, which has a rock cliff of equal or greater height, is 

 turned toward the ice cliff of Hubbard Glacier, 6,000 feet 

 distant. The wind waves that reach it from Russell Fiord 

 have only two miles at most in which to develop. Wind 

 waves from the head of Disenchantment Bay, four miles 

 distant, might reach it, and on rare occasions they probably 

 do, but that part of the bay, being overlooked by the most 

 active part of Hubbard Glacier, is ordinarily full of floating 

 ice, which prevents the generation of such waves. Instead 

 of wind waves the chief attack is by ice-fall waves. From 

 four miles of ice cliff the bergs are breaking, and the cannon- 

 like boom recording the sundering of one of the greater 



