374 



THE DEEP SEA 



% 

 100 



80 



60 



AO 



20 



1 



^ 5 



10 years 



Fig. 3. Distribution of the activities of radium (1), uranium (2), and ionium (3) 

 with respect to the age of the sediment layers, assuming the following ideal con- 

 ditions: (a) the ionium content of each layer of a given core was constant at the 

 moment of its deposition, and exceeded the equilibrium value with uranium by a 

 factor of 50; (b) neither the radium nor the ionium diffuses after deposition of the 

 sediment; (c) the uranium content is constant throughout the various layers. 



out by the Swedish expedition of the Albatross (Koczy, 1956) 

 headed by H. Pettersson. The concentration of radium appears to 

 vary more widely than that of uranium, with values from 0.3 to 

 3 X \0-^^ g/ml, the mean value being taken as 0.8 X 10"^^ g/ml 

 (Koczy, 1956). These early results pointed out a very important 

 fact, namely that the radium in the ocean is not in equilibrium 

 with its parents, U^^^ It will be noticed (Table I) that, in fact, 

 the number of disintegrations of radium per milliliter of water is 

 of the order of 10% of that of U^^^^ 



As early as 1937, Pettersson suggested that this situation could 

 be ascribed to the precipitation, not of radium itself, but of its 

 parent, ionium (Th^^'').The first direct measurements carried out 

 on ionium and other isotopes of thorium by Koczy et al. (1957) 

 confirmed this hypothesis. These measurements have since been 

 repeated by Sackett et al. (1958), using more representative 

 samples, and their work confirmed the former. 



Table I permits the following conclusions to be drawn with 



