423 



Manganese accumulated in this manner lias been found by llie 

 author in more than one locality. 



A good example of this mode of occurrence is given in a complex 

 c»f upper-triassic deep-sea deposits in the left slope of the valley of 

 the Noil Bisnain, near the track from Kapan to Fatu Naisusu 

 (comiiiordy called the rock of Kapan) in Middle Timor. The ore- 

 bearing portion of this complex of strata is 25 metres thick, and 

 about 10 beds of manganese are found in it closely connected with 

 variegated, siliceous clayshales and cherts with radiolaria, the entire 

 complex being intercalated in strata containing limestones with tests 

 of Radiolaria and shells of llalobia. The beds of manganese vary in 

 thickness between 2 and 30 centimeters. Microscopical examination 

 reveals traces of tests of radiolaria in the ore as well as in the rock. 



4. in thin films on fragments of rock formed by the infiltration 

 of manganese in cracks of the rock from which these fragments 

 were derived. 



In this way manganese is found iniiltrated in tlie cracks of all 

 the shales and in the majority of the cherts of the abysmal series 

 on the islands of Borneo, Timor, and Rotti. 



Thi' chi'mical com/msltion of the nodules of manganese. 



I am indebted to Prof. H. Ter Meulen in Delft for a chemical 

 analysis of a nodule of manganese taken from a marl bed witli 

 concretions of hornstonc, from Sua Lain mentioned previously. 

 The result of the analysis in as follows: 



Nodule of manganese from Sua Lain 

 SiO, 2.9 ') 



Fe,0, + Al,0, 2.3 



MnO, 57.7 



MnO 10.5 



CoO 0.3 



BaO 11.7 



CaO 5.6 



Na,0 1.1 



CO, small quantity 



The substance loses 1.05% of its weight at a temperature of 

 125° (.'.. and 15. S»/, on roasting. 



A similar analysis has been made by Mr. G. Witteveen of the 



1) hi tlie original Dutch edition of this paper erroneously the figure 2.09 has 

 been given for tlie percentage of SiO^. 



