36 Dr. A. S. Eve on the Ionization of the 



Thus we have:-^ 



Penetrating Radiation, RaC. 





Land. 



Sea. 



Air. 



Q 



4-3X10" 12 

 2-7 



1-4X10 -12 

 130 

 23 

 •80 



MxHf 14 

 10 



1-Ixl0~ 14 



1 



•18 

 •006 



8xl0~ 17 

 •0013 

 6-1 XlO" 14 

 5'5 

 1 



•035 





Q/p 



Ratios 



01' 



Ions/cm. 3 see 



It will at once be seen that the penetrating radiation over 

 the ocean from the radium in the sea is negligible, being less 

 than one-fifth of that from the radium C in the atmosphere 

 over land. Since the radium emanation in the atmosphere 

 over the sea is probably less than over the land, it is altogether 

 quite extraordinary that those observers who have used 

 Ebert's ion-counter, and those who have measured the con- 

 ductivity of the atmosphere over the sea, have found values 

 in each case not much, if any, less than over the land. It 

 is possible that the greater purity of the air over the ocean — 

 the absence of dust and smoke and physical impurities of 

 that kind — may cause the small ions over the ocean to remain 

 small ions, except during time of actual fog, while over the 

 land they tend to become large ions. Yet such an explana- 

 tion is very doubtful, and in this discrepancy lies at present 

 our chief objection to a purely radioactive theory of atmo- 

 spheric ionization. It is a question on which further investi- 

 gation is needed, before any weighty opinion can possibly be 

 hazarded. 



We get a sidelight on this interesting and difficult point 

 in the action of Hertzian waves in wireless telegraphy, which 

 appear to have a larger effective radius in the dark, or during 

 mist or fog, and are to a considerable extent absorbed in the 

 presence of sunlight. It is possible that the small ions both 

 render the air a conductor and tend to absorb or disperse the 

 Hertzian waves, and that the sunlight may itself produce 

 small ions. There appears to be no direct evidence of the 

 influence of sunlight increasing the ionization near the earth's 

 surface, but if the electrons were freed a little from the 



