53 
unavoidable that the sandstone fragments have arrived at their 
position by sinking down through the augite-syenite at a time 
when the latter was still in a molten condition. We are in- 
duced to consider from this, that the magma of the augite- 
syenite had a lower specific gravity than the sandstone, and 
that this condition has played some part in the mechanism of 
intrusion of the magma. 
There is also a second feature of great theoretical interest 
in connection with the sandstone fragments of the augite-syenite. 
All these fragments, the large as well as the small, are sepa- 
rated from the augite-syenite by a zone of soda-granite, which 
sends out small apophyses into the sandstone and frequently 
contains a large number of very small rounded fragments of 
the latter. The width of the soda-granite veins is very variable, 
usually 1/2—2 meters. In the neighbourhood of the sandstone 
fragments, but without apparent connection with them, there are 
irregular and branched veins, 0°1—0°5 meters broad, of soda- 
granite in the syenite, and at one place a quantity of small 
(up to the size of a fist), globular masses of coarse-grained 
soda-granite was found enclosed in the syenite. 
This soda granite consists of yellowish-white felspar and 
light grayish, almost transparent quartz; in addition, it contains 
black minerals, which look like arfvedsonite to the naked eye, 
but under the microscope they prove for the most part to be- 
long to other alkali-bearing kinds of the amphibole and pyroxene 
(ægirine, ægirine-augite, and catophorite-like hornblende). In 
the above-mentioned veins the soda-granite is medium-grained, 
but in the zones round the sandstone fragments it is usually 
coarse-grained. Directly surrounding the sandstone there is 
always a black zone, not more than !/s a centimeter broad and 
containing exclusively black-green pyroxene or black hornblende 
in short prisms which lie at right angles to the surface of 
contact; then comes a slightly broader, white zone, which 
consists of large anhedra of felspar and quartz with a relatively 
