258 Ionization of the Atmosphere over the Ocean. 



no increase in the electrification. The increase, when water 

 was present, was probably cine to the friction between the air 

 and water. McLennan observed the high negative potential 

 of the spray from Niagara Falls, and found it sufficient to 

 maintain an insulated wire at 7000 volts. When the wind 

 breaks the tops of the waves at sea and forms " white horses/' 

 electrification may be caused which will increase the apparent 

 number of ions observed at sea. 



Summary. 



I. The ionization of the atmosphere over the North Atlantic 

 Ocean appears to be approximately the same in magnitude 

 as in Europe or North America. 



II. The amount of radium contained in sea-water is very 

 minute, and is 1/500 to 1/2000 part of the average 

 amount determined by Strutt in various sedimentary 

 and igneous rocks. 



1 IT. Specimens of sea-water obtained from mid-Atlantic, and 

 a sample of sea-salt, indicate that 1 gram of sea-water 

 contains about 5 X 10 — 16 grams of radium. 



IV. The emanation from the radium in sea-water, and the 

 penetrating radiation from the active matter contained 

 in it, are insufficient to account for the ionization observed 

 over the ocean. 



V. Emanation arising from radium on land, and carried to 

 to sea by the wind, is the only known cause which will 

 account for the ionization effects observed over the 

 ocean. The ionization observed is larger than would be 

 anticipated from such a cause, but it is possible that the 

 rate of recombination of ions over the sea may be less 

 than over the land. 



I am grateful to Professor Rutherford for helpful dis- 

 cussion and suggestions. I wish also to thank Mr. C. H. T. 

 Newton, and the captain and officers of S.S. "Athenia " and of 

 s.3. " Hibernian " for their kind assistance. 



Montreal, December 1906. 



