DEEP-SEA RADIUM 



117 



precipitation at a constant rate, the time span over 

 which this radioactive age-determination method can 

 be used must be limited to a maximum of 300,000 to 



Fig. 38. Equipment for radium measurement 



400,000 years, after which the residual radium-ionium 

 content becomes too far reduced for accurate radium 

 determinations. Unfortunately, later experiments have 

 proved that such favorable conditions are rarely met 

 with in nature. The time span within which the method 



