URANIUM AND GEOLOGY JOLY. 



361 



surface material open to our investigation. As the mean of a very 

 large number of exjDeriments upon 22 different samples of sea water 

 from various widely separated parts of the ocean, I obtain a mean 

 of 0.016X10"^- gram per cubic centimeter. There is considerable 

 variabilit3\ Taking the mass of the ocean as 1.458X10^® tonnes, 

 there must be about 20X10^ grams (20,000 tons) of radium in its 

 waters. 



The experiments which I have been able to make on deep-sea de- 

 posits, thanks mainly to the kind cooperation of Sir John Murray, 

 apply to 10 different materials of typical character. 



The results are so consistent as to lead me to believe that, although 

 so few in number, they can not be far wrong in their general teaching. 



The means are : 



Radium. 



Extension 



(millions of 



square 



miles). 



Globigerinaooze, 

 Radiolarian ooze 

 Red clay 



7.2 

 36.7 

 33.3 



49.5 

 2.5 

 51.5 



Diatom oozes have not yet been examined. 



It is apparent from these results that the more slowly collecting 

 sediments are those of highest radio-activity, as if the organic mate- 

 rials raining downward from the surface of the ocean carried every- 

 where to the depths uranium and radium abstracted from the waters, 

 but in those regions where the conditions were inimical to the preser- 

 vation of the associated calcareous tests there was the less dilution 

 of the radio-active substances accumulating beneath. The next table 

 shows that radio-activity and the percentage of calcareous matter in 

 these deposits stand in an inverse relation : 



Globigerlna ooze: 

 Challenger 338 

 Challenger 296 



Red clay ooze: 

 Challenger 5 . . 

 Challenger 276 



Radiolarian ooze: 

 Challenger 272 

 Challenger 274 



Calcium 

 carbonate. 



Per cent. 

 92.24 

 64.34 



12.00 



28.28 



10.19 

 3.89 



Radium. 



6.7 



15.4 

 52.6 



22.8 

 50.3 



The percentages of calcium carbonate are from the report of the 

 Challenger expedition. The red clay in the table, which reads as an 



