1201 
sharply separated from a brown bordering zone. Finally, small 
crystals of apatite and fine ore-particles occur in these rocks. In the 
left branch of the S% Pakis near the kampong Pakis, the first solid 
rocks found in situ are granites with a parallel-structure often apparent. 
It is highly probable that in the part not exposed between the 
granites and the Sei Pakis, the zone of the feldspar hornfels. and 
granite apophyses occurs, which ‘farther up the river is exposed. 
The granites at the contact contain much biotite, the increase of the 
percentage of biotite being a common phenomenon of endomorph 
contact-metamorphism. This fact may here account for the high per- 
centage of mica, although elsewhere in the granitic area, rocks 
containing much biotite also occur. 
VerBEKK *) describes dark gray, sometimes black hornfels containing 
feldspar, from Pamoesian near the river Sinamar in the Ngalau- 
Sariboe mountains. The percentage of feldspar (chiefly plagioclase) 
is only contained in the contact-rocks just touching the granite, as 
soon as we get away from the granite more than. 2 or 3 m., the 
percentage of feldspar diminishes and ‘soon. totally disappears. Appa- 
rently we have to do here with contact-phenomena equivalent to 
those mentioned above. 
Putting together the data obtained in several localities, the following 
statement may be given on the nature of the contact-metamorphism. 
1. At the contact of the granites a narrow zone of the surrounding 
schists has heen feldspathised. The contact rocks almost graduate 
into gneisses, and the sharp contrast between igneous rock and 
sediment has disappeared. Granite apophyses occur in alternating 
layers with the schists. Farther away from the contact this feld- 
spathisation is entirely missing. 
2. In the hornfels the original stratification of the rocks has 
been conserved. 
3. biotite is the mica found in the feldspathised hornfells near 
the contact with the granite, muscovite appearing in the contact 
metamorphosed ‘rocks farther away from the contact. 
4. The zone of the contact rocks with Al-silicates (andalusite ete.) 
is missing, the zone of the mica schists succeeding the feldspathised 
zone *). 
5. Tourmaline is a common mineral in the contact-metamorphie 
rocks. 
1) R. D. M. VeRBEEK, loc. cil. p. 179. 
2) “Knolenglimmerschieler”’ and ‘“Kuotenthouschiefer’ were not met with, but 
the author considers undecided whether they are entirely missing or not, 
