424 



small nodules of manganese mentioned above, wliich have been 

 oollected bj Verbkek ') iji piistocene marl near Bebalaiii on the island 

 of Rotti. The result of tlieir analyses was as follows: 



Nodnle of manganese from Bebalain 



/not determined 

 alkalis ) 



Obviously there is a great similarity in chemical composition 

 between the concretions of manganese from Sua Lain and those of 

 Bebalain. Baryum figures highly in both the analyses. Comparing 

 these two analyses with 45 analyses -) made from concretions of 

 manganese dredged by the Challenger tVom recent deep-sea deposits, 

 the proportion of iron proves to be low in the mesozoic nodules of 

 Rotti. In recent nodules of manganese from the deep-sea the propor- 

 tion of iron, determined as oxyde of iron, varies from 6.46 to 46.4. 

 The proportion of manganese determined as MnO, in these two 

 extreme eases proved to be 63.23 and 14.82 respectively. 



On the relations hetiveeii the concentration of mnngane.se in the 

 foiin of (/rains and of nodules. 



It is not an easy matter to study the manner in which the accu- 

 mulation of manganese in recent deep-sea oozes lakes place, because 

 in the process of dredging the samples from a gi-eat depth, the 

 sediment is agitated more or less and therefore the sample does 

 not show any more the original position and mutual arrangement 

 of the grains and the nodules of manganese in the mud or ooze 

 at the bottom of the ocean. As soon as, however, the deep-sea 

 ooze is cemented into rock as is the case with these deposits of 

 former geological ages the mutual arrangement of the grains and 

 nodules of manganese is no more modified, and can be studied under 

 the microscope in slides made of these rocks. These slides will show 



') R. D. M. Verbkek I.e. p 393. 



'; J. MuRRAi' and A. F. Renard I.e. p. iG4— 487. 



