16 
The dark-coloured rocks of the volcanic series compose 
the highest of the plateaus, the Ilimausak plateau, which rises 
above the snow-line and is therefore covered with a cap of 
snow and ice. From this cap, small glaciers descend on all 
sides giving rise by their erosion to picturesque cirques with 
precipitous walls and separated by bastion-like projections of 
the plateau. The flat snow-cap which has an altitude of about 
1100 meters is surmounted by two higher summits; the highest 
of these is a somewhat rounded and partly snow-covered hum- 
mock which the Greenlanders have named Ilimausak, a term 
denoting the plug upon the fore-end of the shaft of the har- 
poon, used for keeping the detachable bone fore-shaft in its 
right position. 
A very conspicuous feature of the sandstone formation is 
the presence of numerous dark-coloured dykes and sills. The 
sills are more common in the upper than in the lower horizons, 
and they constitute no unimportant part of the total thickness 
of this formation. The dykes are very regular and almost all 
of them run in a N.E. to S.W. or Е. М.Е. to W.S. У. direc- 
tion, parallel to the main direction of the fjords. As the power 
of resistance of the dykes and sills to erosion and weathering 
is different from that of the sandstone, they influence the de- 
tails of the surface relief in numerous ways. 
Igaliko Sandstone. — This is a red-coloured or brownish- 
red sandstone, fairly hard and resistant to weathering. It is 
composed of well-rounded grains of quartz mixed with a vary- 
ing, but usually very small, amount of felspar grains. The ce- 
ment is siliceous or, rarely, ferruginous. The outer appearance 
sometimes approaches that of a quartzite; in such cases the 
microscopical examination shows that the quartz-grains have 
been secondarily enlarged at the cost of the cement. Ripple- 
marked surfaces are often to be seen. 
In several places there occur thin, subordinate beds of a 
dark gray shale in which fossils have been sought for in vain. 
