Manganese nodules and oceanic radium 



343 



column found from the measurements already quoted and set out in Tabic IV. The 

 curves are seen to have maxima in the uppermost water layers, then to fall to inter- 

 mediary minima at a depth of about 1,500 metres (possibly due to biologic extraction) 

 and, after rising again to a maximum in a depth of 2,000 to 4,000 metres, attaining 

 even higher values in still greater depths. 



As has already been pointed out here on pp. 335 and 339, the passing over of radium 

 from the sediment surface-layer to the manganese nodules resting on it speaks in 

 favour of a solution of radium near or in the sediment surface actually taking place. 



Accepting Dr. Koczy's explanation as plausible, we arrive at a rather unexpected 

 picture of the origin of the radium in ocean water. 



The ancestral element uranium is being carried into the ocean by rivers from 

 denuded rocks on the continents. The ionium produced from the dissolved uranium 



w 



6000 



SOOO V 



/S ■ /0~^yPa//n/ 



Fig. 3 



is very efficiently removed from solution through precipitation, and settles over the 

 ocean bottom, there giving rise to its descendant radium. The radium in the upper- 

 most few centimetres of the sediment passes readily over into solution, some oi it 

 becoming reprecipitated or adsorbed together with manganese in the nodules. Another 

 part which has become dissolved from the sediment is distributed through the super- 

 natant water masses, giving them a radium content inlermcd.atc between that in 

 equilibrium with the dissolved uranium and the much lower quantity in equilibrium 

 with dissolved ionium. 



