LAKES AND VALLEYS OF NUGSUAK PENINSULA 657 
pool. The largest water bodies are confined for the most part 
to the large valleys; but many tarns are scattered over the higher 
lands. Bothtypes are, with one or two possible exceptions, true 
rock-basins, since they are entirely surrounded by rock in place ; 
for there is rarely enough till for a dam. Based primarily on 
origin, the lakes are grouped under ‘‘ Rock-basins due to glacial 
origin,” and on position, are further grouped as (a), highland, 
and (0), valley lakes. 
ROCK-BASINS OF GLACIAL ORIGIN 
The highland lakes.— On account of their salient features, not 
all the highland lakes can be ascribed as the direct products 
of glacial erosion; but it is certain that all of them owe their 
origin, either entirely or in part, to glaciation. Therefore, since 
this class is in part directly and in part indirectly the products of 
glaciation, and since no differentiation of those that are ice- 
scoured basins from those that are perhaps only partially due to 
glaciation, can be effected, they are both grouped as highland 
lakes of glacial origin. 
This entire group of lakes is composed of small tarns and 
pools of very shallow depth. Their distribution is apparently 
controlled entirely by the weaker rock structure. Where the 
joint planes were numerous and intersected, tiny lakes were often 
found. Generally, the larger highland basins were found 
developed in the direction of the strike of the gneiss, and had 
resulted from the removal of the softer layers of gneiss, by some 
process of erosion. Still others were observed where these 
planes of weakness were not apparent, but, in some cases, could 
probably be ascribed to the result of chemical or mechanical 
weakness, due to mineral distribution. The lakes are prevailingly 
irregular in outline, and contain varying amounts of weathered 
débris scattered over the bottoms of their basins, which is very 
probably due to recent action. 
Their size, distribution, position and intimate relationship to 
rock structure, and irregularity of outline are sufficient evidence 
of their having resulted, in part, from differential atmospheric 
