573 
Strait, the western part of Java has been moved several tens of 
kilometers towards ‘the South in regard to South Sumatra. Where 
fractures are gaping it is not necessary, as has been said, for them 
to be inclined to the geanticlinal axis, in order to bring about an 
extension of the geanticline. It is possible that the gaping along 
transverse fractures has contributed to the origin of Sunda Strait 
and, as a matter of course the transverse movements will not pro- 
ceed horizontally, but will have had a vertical component, which 
is not expressed in the movement of the horizontal projection, our 
only object of inquiry. In the Jura mountains we know only move- 
ments along fault-planes without gaping, but here the movement, 
now visible after erosion, took place under an overlying load of 
sediments. The arrangement of the faults is harmonic here, and 
consequently shows its alliance with the flow at greater depth. 
Several factors near the surface, as the composition and the strati- 
fication of the rocks, exert a stronger action to disturb the harmonic 
structure. 
The horizontal movement of a geanticline, which proceeds in the 
direction of a continental ““Vorland”, depends on the shape and the 
distance of the “Vorland”. If the shape is irregular, considerable 
differences in velocity for neighbouring points of the horizontal 
projection of the geanticlinal axis may occur and considerable faulting 
movements may take place. 
The row of islands Timor-Tenimber islands afford an illustration 
of a geanticline moving in the direction of a “Vorland” with an 
irregular shape). The 200 m.-line of the Sahul shelf presents an 
abrupt right-angled bend south-east of the east point of Timor and 
a less abrupt bend south of the Island Jamdena of the Tenimber group. 
Opposite the “Vorland”, between the two bends, the islands of the 
Sermata and Babber group lie in irregular arrangement. The non- 
harmonie northern position of the island Kisser may e.g. be allied 
with transverse faults, right in the prolongation of the N.W—S.E 
part of the projecting angle of the 200 m.-line of the Sahul shelf. 
No doubt a number of younger and older faults and, fractures 
are to be found in and between these islands, and we find that 
elements of quite different geological composition lie side by side. 
So, for instance the island of Kisser bears, in geological composition, 
resemblance to the island of Letti; the rocks of these two islands, now 
most probably displaced relatively to each other, may have been 
1) H. A. Brouwer. On the Crustal Movements in the region of the curving 
row of islands in the Eastern part of the East-Indian Archipelago. Proc. Kon. Ak. 
ve Wet. XI ps. 7°74. 
37 
Proceedings Royal Acad. Amsterdam. Vol. XXill. 
