204 
D. Essexite, Tofteholmen, Holmestrand, Norway. У. Зенмегск, 
analyst (W. С. Bröscer, Die Eruptivgesteine des Kristiania- 
gebietes Ш, 1898, р. 83). 
one might have expected that the analysis would have given 
particularly high figures for this element. But as a comparison 
will show. this is not the case, even if it is taken into соп- 
sideration that the iron may be supposed to be partly replaced 
by titanium. It is of interest to note this circumstance as the 
magma of the Narsak essexite must be presumed originally 
to have contained a surplus of iron, a surplus which has 
been laid down in the magnetite-pyroxenite mentioned below. 
Another interesting feature is the very low percentage of 
potash in the analyzed specimens of essexite from Narsak. 
This figure is the only one deviating considerably from what 
must be counted as typical. Nevertheless it cannot be taken 
as a sign of any essential difference between the Narsak type 
and the ordinary essexite type, for as already mentioned the 
potash-felspar content of the Narsak-essexite is locally variable: 
in thin slices of the analyzed specimens | have not been able 
to detect any orthoclase, whereas this mineral has been found in 
no inconsiderable amount in the essexite-specimens from various 
other localities (the island at Narsak, Sigsardlugtok, Kanger- 
dluak) where the rock does not otherwise show any deviations 
from the analyzed variety. 
MAGNETITE-PYROXENITE. 
The magnetite-pyroxenite oceurs within the essexite area 
at a locality about 2 kilometers north-west of Narsak (p. 97). 
It is a fine-grained rock of black colour. It is strongly mag- 
netic and sometimes possesses polarity. Under the microscope 
it is seen to be made up of pyroxene, iron-ore, olivine and 
biotite. All these minerals form more or less isometric grains 
