209 
grains. Augite is abundantly present in small rounded grains, 
0:01—0:06 millimeter in diameter, evidently all formed by the 
metamorphism of the rock. The apatite is in small needles 
and the iron-ore in grains of varying size (0'005—0'1 milli- 
meter) sometimes surrounded by a yellow biotite. 
The chemical composition is given in the table above from 
which it will be seen that the composition is of essexitic type. 
A comparisun with the analysis of the Narsak-essexite (p. 203) 
shows for the essexite-porphyrite more silica, alumina, and 
alkalies, and less titanic acid, iron oxides, and magnesia. This 
corresponds with the circumstance of the rock being extremely 
rich in felspar-phenocrysts and poor in ground-mass. 
ROCKS OF THE VOLCANIC SERIES. 
The volcanic formation rests on the red sandstone and is 
built up of a large number of sheets, some effusive, others 
intrusive. The total thickness is about one thousand meters. 
The original thickness was probably much greater, this forma- 
tion being the uppermost in South Greenland and having been 
exposed to erosion through enormous periods. It constitutes 
the highest snow- and icecovered part of the Ilimausak moun- 
tain group and only in very few places stretches down to the 
level of the sea. During the field work it has been impossible 
to subject this formation that is so difficult of access, to any- 
thing but a very cursory examination. 
Rocks of quite similar character occur as dykes and sills 
in the red sandstone. They are here classed with the volcanic 
series. 
In the following pages a few typical examples will be de- 
scribed, the aim being to give a general idea of the character 
of the rocks and to show the relationship or consanguinity 
with the rocks described in the foregoing chapter. According 
XXXVIII. 14 
