(143) 
which is always coloured bright red and contains more clay and 
iron and less silica than the first type. Radiolaria occur in it in 
variable quantity, but always much less than in the first type. 
The two types pass one into the other quite gradually and all 
sorts of intermediate types occur. The distinct stratification of the 
cherts of the Danau-formation is caused by thicker strata of pure 
Radiolarian hornstone alternating with thin layers which contain more 
clay and less Radiolaria. 
Both types and all intermediate stages agree in this respect, that 
they do not contain any constituents indicative of a terrigenous 
origin, and that the organic remains they contain all belong to 
Plancton organisms with siliceous tests, chiefly Radiolaria. 
In an uncemented state, in which such deposits are still continually 
laid down on the bottom of the oceans at the present day, the 
deposits of the first type are called Radiolarian ooze and those of 
the second type red clay. Radiolarian ooze and red clay gradually 
pass one into the other, and only differ in the percentage of organic 
remains they contain. Murray, for instance, places the limit between 
red clay and Radiolarian ooze at a point where 20% of the deposit 
consists of tests of Radiolaria. It has been observed, that such 
deposits only occur in those parts of oceans which are far removed 
from land, and then again only in the very deepest portions. 
This is explained by assuming that at very great depths calcium 
carbonate is dissolved by sea water, so that of the tests of the 
Plancton organisms,which continually sink down to the bottom of 
the sea only the siliceous tests ever reach the bottom in such depths, 
and consequently they alone are deposited and preserved. 
As soon as one assumes that Radiolarian ooze and red clay are 
oceanic, abyssic sediments, deposited at very great depths, then, on 
account of the complete agreement, between Radiolarian hornstone 
and Radiolarian ooze on the one hand, and between red, cherty 
clay-shale and red deep-sea clay on the other hand, one must also 
conclude that the cherty rocks of the Danau-formation in Borneo 
are oceanic, abyssic sediments. It follows then further that at the 
time when these sediments were deposited, which was probably in 
the jurassic period, the greater portion of Borneo was the floor of 
a deep sea far away from land of any importance. 
The view, which forms the starting point to this conclusion, and 
according to which calcium carbonate is dissolved by sea water at 
great depths, has been subjected to criticism bij Thoulet 1 ), a criticism 
b I. Thoulet. Precis d’analyse des fonds sous-marins actuels et anciens p.p. 16 
en 33. Paris 1907. 
