34 ROYAL SOCIETY OF CANADA 



Let us suppose the ocean contains 9 x 10~^^, the deep sea deposits 

 25 X 10~^^ (Joly), and the sedimentary rocks 1.1 x 10~^^ (Strutt), 

 in each case in terms of grams of radium per gram of material. Take 

 the mean depth of the ocean as 3.5 kilometres and the specific 

 gravity of the deposit or soil as 2.5. Then the amount of radium 

 in 3.5 km. depth of ocean, per sq. cm., is about equal to that, also 

 per sq. cm., in 114 cm. of sedimientary rock, or 5 cm. of deep sea 



deposit. 



Summary. 



1. Radium emanation may be collected over water or over 

 mercury with about equal accuracy when testing for the quantity 

 present in a given solution. 



2. The result of testing six samples of sea-water from the 

 North Atlantic leads to the average value of 9 x 10~^^ gram of 

 radium per gram of sea-water. This is about one-seventeenth of 

 the value found by Joly. 



