218 
about 800 meters, at North Siorarsuit in the talus at the foot 
of Mount Hatten and come from the upper part of this moun- 
tain’. 
Microscopic characters. — The reddish-white felspar- 
phenocrysts have varying forms. Most of them are rather 
isometric with short-tabular or square or rounded forms, a few 
are thick-tabular. Their greatest diameter seldom exceeds 5 
millimeters and is in some cases parallel to the a-axis, in others 
parallel to the vertical axis. They are as a rule very impure, 
filled with minute brownish particles, small dots of iron-ore, 
and a little larger scales of colourless mica. Their index of 
refraction is a little lower than that of Canada balsam. The 
optic examination shows that the felspar-phenocrysts are of 
various kinds. In sections parallel to (010) some of the cry- 
stals show an extinction-angle of — 5° in their central part; 
in the marginal zone this angle is greater and may reach about 
— 10°. In other crystals the extinction-angle is considerably 
greater both in the central portion and the marginal zone, 
varying between + 14° and + 19°. In both kinds of crystal 
locally an indistinct cryptoperthitic striation is seen, making an 
angle of + 66° to + 70° with the cleavage-traces. In sections 
perpendicular to (010) the extinction-angles vary in the dif- 
ferent sections from O° to about 17°; some of the crystals 
show a fine and irregularly granular twin-structure and others 
a not very distinct twin-striation parallel to (010). In the latter 
case the extinction-angles are always very small. These ob- 
servations show that the felspar-phenocrysts are alkali-felspars 
of the soda-microcline series (anorthoclase) with a composition 
! The upper part of this mountain is not accessible as it is too steep, 
but at a height of about 1090 meters specimens were taken from the 
wall of the rock immediately above the arfvedsonite-granite. These 
specimens agree with those taken among the fallen boulders in the 
talus with the exception that they are still more intensely meta- 
morphosed. 
