248 Mr. A. S. Eve on the Ionization of 



(6) i/r 3 increases as the induction decreases, and tends to a 

 limiting value of about 60° when B x is zero. 



(7) Increase of frequency largely increases the total iron 

 loss, but, owing to the uncertainty as to the eddy-current loss, 

 it could not be said what part of this increased iron loss was 

 due to an increase of hysteresis. 



(8) For such a rod, the formula for the eddy-current loss 



w ttA $ 2 



Bb VT 



calculated on the assumptions that fi is constant and -=— 



constant over the section gives results which in some cases 

 must be too large. 



The work described in this paper has been performed in 

 the Physical Laboratory of the Melbourne University, and 

 I have to record my thanks to Professor Lyle for his' kind- 

 ness in placing the resources of his laboratory, and in 

 particular his wave-tracer, at my disposal, and for his help 

 in preparing this paper for publication. 



XIV. The Ionization of the Atmosphere over the Ocean. 

 By A. S. Eve, M.A., McGill University, Montreal*. 



IT is important to ascertain if the ionization of the 

 atmosphere over the ocean is equal to the ionization of 

 the atmosphere over the land. If the radium emanation in 

 the atmosphere, and the penetrating radiation due to radium 

 in the earth, are together the main causes of the ionization 

 of the atmosphere near the surface of the earth, then it 

 might be expected that the ionization over the land would be 

 greater than that over the sea. For experimental evidence 

 at present obtainable indicates that radium is present in sea- 

 water to a markedly less degree than in the sedimentary 

 rocks on land. And, since radium emanation decays to half 

 value in four days, the wind is unable to transport the 

 emanation from land to places in mid-ocean before the activity 

 is materially decreased. 



Unfortunately, but few observations of the ionization of 

 the atmosphere have been made in mid-ocean. However, 

 A. Boltzmann f made daily observations with an Ebert's 

 instrument during a voyage from Dover to New York, 

 Aug. 21-31, 1904. He found the number of ions present 



* Communicated by Professor E. Rutherford, 

 t Physikalische Zeitschrift, 6 Jahrganz, No. 5. 



