232 
blocks, or islands in our case, as well as every range of sunken 
blocks, or deep sea basins in our case, must indicate the position 
and the trend of the major folds, which are in mode of formation 
at a certain depth; thus the character of the deeply seated folds 
would be found reflected in the surface topography. 
But then one has to take into account also, the submarine topo- 
graphy *) and fortunately the excellent deep sea chart of the Siboga- 
expedition enables us to do this *). | 
The most salient feature on this map is the striking difference 
which exists between the western portion (the Java-sea and its 
surroundings), and the eastern portion (the Molucca-sea). The latter 
exhibits a complicated topography and great variations both in the 
depth of the sea and in the heights of the numerous islands, which 
generally emerge boldly from the sea; whereas the western area 
shows a slight and very uniform depth of the sea and smooth out- 
lines of land which rises with a very gentle slope from the coast *). 
1) In my opinion it is imperative to study the submarine topography, because the 
part of the surface of the earth hidden beneath the sea in this archipelago is so 
much greater than that of the islands. This itself is a favourable circumstance, 
because it tends to prove, that the basins until now were comparatively little 
filled up by products of erosion brought from the land, and consequently the 
surface topography originated by the recent crustal movements has been fairly 
well preserved at the bottom of the sea. The upraised islands of course are 
smaller and less high now than they would have been, were it not that the 
erosion had from the start counteracted the results of the upheaval. In or near 
large continents the chances for the preservation of a salient topography are 
much smaller, because the original features would have been much sooner oblite- 
rated by the effects of erosion and sedimentation. Thus in a portion of Northern 
Germany and the Netherlands, geologically not long since, crustal movements 
formed a surface topography, certainly not less complicated than that of the East- 
Indian archipelago, in which the levelling processes have been so powerful, that 
its original topographical details has become obliterated, with the result that at 
present only a trace of them can be seen at the surface; indeed we have to 
imagine the quaternary and a portion of the tertiary deposits removed to be able 
to realize the complexity of this topography. 
2) G. A. F. Typeman. Hydrographic results of the Siboga-expedition. Chart 1. 
Part Ill of M. Weger. Siboga-Expeditie. Leiden 1903. 
Soundings which have been made in the archipelago since the results of the 
Siboga-expedition were published, have proved, that the submarine topography is 
still more complicated than that shown on the chart. Very probably, the most 
important result of the researches of the Siboga-expedition i. e. the existence of 
a strikingly complicated submarine topography in the eastern parts of the East- 
Indian archipelago, wil! be more accentuated by future researches. 
3) VERBEEK has already drawn attention to this striking difference between the 
western and the eastern portion of the archipelago and he pleads a causal origi- 
nation for the presence of the deep sea-basins and the islands with elevated 
