Atmosphere due to Radioactive Matter. 35 



be made is of an uncertain character *. An increase in the 

 value of q will affect the value of n, which is already in 

 excess of that observed. Yet with every allowance for the 

 value of q, due to penetrating radiation, the theoretical value 

 appears to be smaller than the observed. We may deduce 

 either that the radioactive matter in the earth has been under- 

 estimated, which is improbable, or that the value found for 

 K is too small, or that the observed values of q are too great, or 

 that radiation exists of a type not yet expected or discovered 

 proceeding from matter rather than from radioactive 

 matter. 



Ionization over the Ocean. 



It would be interesting to make a table corresponding to 

 that given above (15), but with values for mid-ocean. Un- 

 fortunately we have no certain measurements of the mean 

 quantity of radium or thorium emanations over the ocean. 

 From experiments by many observers, it appears that sea 

 breezes on the western side of a continent contain less 

 radium C than do land breezes. It is, however, certain that 

 radium C does exist over the ocean in measurable quantities, 

 and there is little doubt that radium emanation escapes from 

 the ocean with greater facility than from the land, and this 

 fact compensates to some extent for the minuteness of the 

 radium contents of the ocean as contrasted with the land. 

 There is also some uncertainty as to the mean value of the 

 amount of radium in sea water, for Joly (Phil. Mag, 

 Sept. 1909) has found 1*1 x 10~ 14 gramme of radium 

 per cm. 3 for sea-water from various localities, and I have 

 found 10~ 15 for sea-water from the middle of the North 

 Atlantic. For the present we will take the higher value 

 given by Joly. The ratios of the penetrating radiations 

 from the RaC in land, sea, and air are then, necessarily, near 

 the earth's surface, as 



Qjp : Q'/p' : Q"./>", 



where the Q's denote quantities of radium C per cm. 3 , ex- 

 pressed in equivalent grammes of radium, and the p's denote 

 the respective densities. 



* If equal to radium we get 3x0-8 = 2'4 ? agreeing with Wright, 

 see (1-5). 



D2 



