230 THE SEA FLOOR 



areas, especially the border regions, are the most 

 unstable. 



From a recent examination of some " Challenger " 

 deposits sent to him from the " Challenger " Office, 

 Professor J. Joly has been able to give the radium 

 contents of deep-sea deposits. He finds that the Red 

 Clays and Radiolarian Oozes contain much more 

 radium than the Globigerina Oozes or terrigenous de- 

 posits ; in fact, the radium content is greatest where 

 the rate of deposition is believed to be the least. The 

 idea at once suggests itself that this is connected with 

 the greater amount of cosmic dust in the deep deposits 

 far from land. This is well worthy of the attention of 

 those who in future may dredge up large samples of 

 deposits from the Red Clay areas. 



