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. vm) 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 
