411 
B Sea-tin workings in drowned river-beds at 
the coast of the island of Singkep. 
(il Tin-deposits now worked out. 
Scale 1 : 50.000. 
Fig. 2. After a sketchmap in possession of the Direction of the Singkep Tin Company. 
gical time no negative shifts of the shore-line of any consequence 
have occurred there. 
d. Traces of subsidence; drowned and sunken rivers. 
On the contrary there are indications of subsidence of these coasts, 
or, which comes to the same in our argument, of rise of the sea-level. 
The way in which the large muddy rivers of Sumatra and of 
Borneo debouch into the sea, is peculiar. The absence of deltas, as 
well as their wide funnel-shaped mouths — very conspicuous with 
the Sampit — and the great depths in the lower courses of the 
rivers point to positive shifts of the coast-line. 
Only one of them, the Kapuwas, which carries more sediment 
than any of the others, has formed a delta, which, however, hardly 
protrudes from the coast-line into the sea. 
Furthermore, the traces of the rivers of the Sunda-peneplain, 
27 
Proceedings Royal Acad. Amsterdam. Vol XXill. 
