type; more rarely a soda-orthoclase exhibiting a beautiful blue 
schiller has been observed. 
It is not improbable that the Usuk type has a wide distri- 
bution in the upper part of the Igdlerfigsalik Mountain which 
has not been visited by the author. At the summit of the 
mountain Dr. Sreexsrrur, in 1888, has collected specimens of a 
weathered and red-coloured nepheline-syenite which belongs to 
the Usuk type. 
Dykes cutting the nepheline-syenite. 
In the nepheline-syenite only a few dykes have been ob- 
served. They belong to the following types: fine-grained nephe- 
line-syenite, tinguaite, and syenite-porphyry. 
Two or three dykes of a fine-grained nepheline-syenite 
were found by Mr. Bücaiz in the large valley east of Usuk. 
These consist of a gray and somewhat weathered foyaite in 
which the prevalent dark-coloured minerals are a brown biotite 
and a diopside with a green marginal zone. One specimen is 
olivine bearing and of a porphyritic structure, showing pheno- 
erysts of microperthite and nepheline which may attain a length 
of two or three centimeters. 
In the coarse-grained foyaite of the mountain west of 
Flink’s Dale in Korok two dykes of finguaite have been ob- 
served. Each is about one meter wide and follows a curved 
course. The rock is dense and of a greenish-black colour. 
Under the microscope the main constituents are seen to be: 
alkali-felspar, biotite, ægirine, and analcime. The felspar is 
very abundant and appears in the slices as small laths, 0°01 
millimeter thick by 0°03 millimeter long, sometimes arranged 
in radiating groups. Some of the iaths are orthoclase, others 
consist of a plagioclase, probably albite. Perthitic intergrowths 
are also common; the combination-surfaces are irregular or 
partially parallel to (010). The analcime is not very abundant, 
it occupies small areas of irregular form and is partly inter- 
