378 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
on the ice (Russell, ’93, p. 240). Having been formed on the ice, 
it is probably to be regarded as the product of a superglacial or 
englacial stream, and not of a subglacial stream, such as Kame 
stream is to-day. 
It appears probable that the principal subglacial streams of the 
Malaspina glacier are but little constrained by the ice, or at least 
that their courses are conformable to the ground topography to the 
extent that they nowhere flow uphill; and quite certainly we may 
assume that they do not show the utter disregard of the topography 
observed in many eskers. In so far as the subglacial streams follow 
closely the axes of the ground valleys, their courses may be regarded 
as virtually fixed, and deposits formed in their channels cannot fail 
of obliteration or burial when uncovered by the recession of the ice; 
and the same fate will, of course, be shared by deposits formed in 
the ice-walled canyons in which the ice tunnels frequently terminate. 
In view of these considerations, it is certainly not surprising that 
truly subglacial eskers are not now coming into view through the 
shrinkage of this lake of ice. The piedmont glacier appears fairly 
comparable in this respect with the tributary alpine glaciers and 
with valley glaciers in general, including the Muir glacier and other 
ice streams tributary to Glacier bay. 
The only features suggestive of eskers yet noted in the detailed 
studies of the Muir glacier are the deposits described by Professor 
G. F. Wright (’89, p. 62) as formed in certain ice tunnels near the 
thin, debris-covered margins of the glacier. These tunnels have 
been abandoned by the subglacial streams which made them, and 
subsequently filled by the sliding in of the superglacial detritus 
through holes in the roofs. Professor Wright says, ‘Hn numerous 
places the roof of this tunnel (which is 25 to 30 feet high) has 
broken in, and the tunnel itself is now deserted for some distance by 
the stream, so that the debris (which overlies the ice to a depth in 
some places of 15 to 20 feet) is caving down into the bed of the old 
tunnel as the edges of ice melt away, thus forming a tortuous ridge, 
with projecting knolls where the funnels into the tunnel are oldest 
and largest. At the same time, the ice on the sides at some distance 
from the tunnel, where the superficial debris was thinner, has melted 
down much below the level of that which was protected by the 
thicker deposit; and so the debris is sliding down the sides as well 
as into the tunnel through the center. Thus three ridges approxi- 
