LAKES AND VALLEYS OF NUGSUAK PENINSULA 663 
beaches. These may represent storm levels, or they may be the 
result of climatic changes. While the valleys probably cannot 
in all cases be ascribed to the same cause, the lakes associated 
with the valleys are, apparently, the result of differential ice 
erosion, and are true rock-basins, since they are walled in by 
rock zm setu on all sides. 
Dust wells and pools on the tce-surface—The marginal surface 
area of the glacier ice was found dotted with numerous circular 
holes, varying from a quarter of an inch to several feet in 
diameter, and averaging probably several feet in depth. These 
were filled nearly to their tops with water, and their bottoms were 
invariably covered with a thick layer of dust. Professor Barton’ 
has described the same condition to the south of this locality 
in the Umanak district, where he states, that the pits are con- 
fined to a marginal zone of about one mile in width, beyond 
which, and towards the interior, the ice surface becomes com- 
paratively smooth. Professor Chamberlin? has observed the 
same conditions farther north along the west coast, and has 
fully discussed their origin in a previous number of this 
JOURNAL. 
Other larger pools were seen. Professor Tarr3 noted an 
especially large one, occupying a depression in the ice, of about 
one quarter of a mile in length in the direction of its longest 
axis, very shallow in depth, and revealing clear smooth ice, 
with no sediment over its bottom. No observation was made 
concerning its outlet, and Professor Tarr states that the pool 
probably represents a case of differential meeting. 
Lakes due to other causes — Along the ice margin, lakes were 
found, in places, formed by the usual ice marginal processes. 
A majority of these marginal lakes are due to a walling in of the 
numerous depressions of the extremely irregular surface of the 
peninsula, by the more or less steep ice-front on one side, and 
the slopes of the depressions of the land on the other. Each of 
U@prcit., pa2 lo: 
2Jour. GEOL., Glacial Studies — Greenland, IV, Vol. III, 1895, p. 215. 
3 Communicated by letter to the writer. 
