

THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



t I 



r— . 



JULY 1910. 



I. On the Amount of Radium Emanation in the Lower Regions 

 of the Atmosphere and its Variation with the Weather. By 

 John Satterly, A.R.C.Sc, B.Sc, B.A., St. John's College, 

 Cambridge *. 



[Plates I. & II.] 



IN the Philosophical Magazine of October 1908 I gave an 

 account of the methods I had employed for measuring 

 the amount of radium emanation in the air. Two methods 

 were used : (1) absorption of the emanation by coconut 

 charcoal, and (2) condensation of the emanation by liquid air. 

 The first method is the more easily performed and gives the 

 more accurate results. In the same paper I described my 

 attempts at finding how the amount of radium emanation in 

 the air was affected by weather conditions. The experiments, 

 however, were not sufficiently sensitive to give any definite 

 results, and the purpose of the following paper is to describe 

 some more accurate experiments made in 1909. 



Full experimental details of the charcoal method are given 

 in my former paper, but it maybe worth while to recapitulate 

 them here as briefly as possible. 



To get the emanation out of the air, the air was drawn by 

 a water-pump through coarsely-powdered coconut charcoal 

 packed in a porcelain or silica tube. In all the experiments 

 the air-stream was kept at a constant value (half a litre 

 per minute), measured by means of a gauge, and regulated 



* Communicated by Sir J. J. Thomson. 

 Phil Mag. S. 6. Vol. 20. No. 115. July 1910. B 



