410 
most likely nowhere beyond 60 km. from it. In February 1894 I 
found at flood-tide before the estuary of the Kapuwas in West 
Borneo the extreme limit of the muddy river-water as far as 50 km. 
from the shore). When considering that the muddy fresh water, 
wedging out seaward very slowly, floats on the specifically heavier 
seawater, and that in seawater the sedimentation proceeds about ten 
times quicker than in fresh water, we may be sure that silt does not 
settle down much farther than those 50—60 km. from the coast. 
When we also bear in mind that, among the rivers, debouching 
into the Sunda Sea, the Kapuwas and the Barito are the largest and 
richest in silt, we feel justified in saying that the limit of silt-deposit 
in the Sunda Sea lies at present between the coast-line and a 
distance about 60 k.m. from the coast. 
The charts of this sea show *) however, that the bottom all over 
the Sunda Sea consists of silt, i.e. as far as 100 km. or more from 
the nearest coast. 
When considering the Sunda Sea to be a peneplain, it is easy to 
understand that the sea, when it gradually flooded that plain 
received then much silt from the many rivers discharging their waters 
into the growing sea, this silt being deposited there at great though 
gradually diminishing distances from the present coast. 
The silt or mud, which nearly all the soundings in the Sunda Sea 
have proved to be the principal constituent of the bottom, may be 
looked upon as a sediment carried down chiefly by the former big 
streams before and during the long period of gradual submergence 
of the pleistocene peneplain. 
c. No traces of upheaval. 
The shores of the islands surrounding the Sunda Sea or emerging 
from it, show no traces of upheaval worth mentioning. If we con- 
sider that in regions where reef-building corals live (as is the case 
with the Sunda Sea, though, when compared with the sea-basins of 
the Moluceas it is poor in reef-builders) every upheaval of the land 
(or subsidence of the sea-level) is almost invariably manifested by 
the emersion and preservation — for a long time at least — of 
reefs, i.e. by so-called elevated coral-reefs, it is obvious that the 
absence of those features nearly everywhere along the coasts of the 
Sunda Sea, warrants the conclusion that in the most recent geolo- 
1) This limit is at the utmost 62 kilometers from the shore. 
*) Since this paper was read new invesligations have been made on the nature 
of the deposits on the floor of the Java Sea They have proved that only in the 
southern half these deposits consist of mud, in the northern half on the contrary 
they consist of sand and sandy loam. 
