75 
the relief from pressure, they will be placed parallel one to the 
other and be surrounded by a felt of aegirine-needles (Kolarocks) ; 
in ease no one-sided pressure prevails, a rock will be formed 
distinguishing itself from: the normal foyaites by the habitus of 
aegirine and arfvedsonite. 
The viscosity of the magma will check the escape of gases, and 
the gradual supply of gases from the underlying magma will oeca- 
sion a transition into rocks of the habitus of the kakortokites, which 
are of an almost identical chemical composition and distinguish them- 
selves from the lujaurites mainly by the increase of the size of the 
grains, by the absence of parallel-structure and by the needleshaped 
habitus of aegirine and arfvedsonite. The again increased pressure in 
this thin fluid magma is converted into a pressure from all sides. 
The regularly returning succession of different variations of kakor- 
tokites was already explained by Ussins by a periodically repeated 
relief of pressure assisted bv separation according to the specific 
gravity. The appearance of narrow transition zones without deviating 
structure between the different variations, and the comparatively 
trifling thickness of the strata prove that the relief of pressure was less 
pronounced during the crystallization of the lujaurites. 
The enclosing of the naujaite-fragments in the breccia-zone can be 
explained by a sinking of the roof, simultaneously with the decrease 
of volume and the erystallization of lujaurites, causing an increase 
of pressure which is favourable to the development of parallel-structure. 
During this process the parallel arrangement of the minerals will take 
place in planes which will bend round the naujaite blocks. 
With a less regular sinking down of the roof, such as seems 
to have taken place in the Pilandsbergen, the pressure and the 
arrangement of the different structures in the batholite becomes 
likewise irregular. The successive periods of relief of pressure and 
the simultaneous escape of gases from the magma may have been 
accompanied by volcanic eruptions of varying intensity. 
Similarity in structures between the crystalline schists and the contactrocks. 
In rocks accompanying lujaurites, we find a great variety of sieve-struc- 
tures which were discussed at large in a former communication’). 
Sieve- and parallel-structures are found also both in crystalline 
schists and contactrocks. This explains why travellers of the first 
half of the 19'* century have mentioned chloriteschists and gneisses 
among the rocks of Greenland, and why Cart Marcu’) enumerates . 
DH. A Brouwer, On peculiar sieve-structures in igneous rocks, rich in alcalies. 
These Proceedings XIV, p. 383. 
2) C. Maucu. Reisen in Siid-Afrika (1865—1872). Ergänzungsheft N°. 37 zu 
PETERMANN’s Geogr. Mittheilungen, p. 14, 1874. 
