A QUANTITATIVE DETERMINATION OF THE RADIUM EMANA- 

 TION IN THE ATMOSPHERE AND ITS VARIATION WITH 

 ALTITUDE AND METEOROLOGICAL CONDITIONS 



By J. R. Wright and O. F. Smith 



{From the Department of Physics, University of the Philippines) 



One text figure 



PART I. A QUANTITATIVE DETERMINATION OF THE RADIUM EMANA- 

 TION IN THE ATMOSPHERE AT MANILA " 



During the last few years the attention of physicists has been 

 directed more and more to a study of atmospheric electricity. 

 A complete study of the problem involves a thorough investiga- 

 tion of several more or less closely related factors, one of the 

 most important being the determination of the amount of radio- 

 active substances in the atmosphere of the earth. 



The presence of radioactive substances in the atmosphere was 

 first conclusively shown by the work of Elster and Geitel ' in 

 1900. Making use of the discovery that an active deposit was 

 collected on a negatively charged wire exposed in the presence 

 of the emanation from thorium or radium, they stretched a 

 negatively charged wire in the open air for several hours. Tests 

 made by the electrical method gave convincing evidence that 

 an active deposit had been collected on the wire from an emana- 

 tion in the atmosphere. The active deposit thus collected was 

 later shown by Bumstead,^ Blanc,^ Dadourian,* and others to be 

 a mixture of the active deposits of both radium and thorium, the 

 relative proportions depending on the length of the exposure of 

 the wire. The first attempt to determine the actual amount of 

 radium emanation in the atmosphere was made by Eve '' by 

 comparing the active deposit collected on a negatively charged 

 wire from a definite volume of air with that collected from air 

 containing a known quantity of radium emanation. However, 

 the uncertainty of this method due to changes in meteorological 

 conditions is so great that it does not afford an accurate means 

 of determining the actual amount of radium emanation in the 

 atmosphere. Eve" and Satterly,^ making use of the discovery 

 by Rutherford * that charcoal made from the shells of coconuts 

 possesses the property of absorbing radium emanation, obtained 



* Much of the equipment for this worlc was furnished by the Bureau of 

 Science, and the work was done in a laboratory of that Bureau. 

 'Phys. Zeitschr. (1901), 11, 560. 'Phil. Mag. (1905), 10, 98. 

 'Am. Journ. Sci. (1904), IV, 18, I. "Ibid. (1907), 14, 724; (1908), 16, 622. 

 'Phil. Mag. (1907), 13, 378. 'Ibid. (1908), 16, 584. 



' Le Radium (1908). 'Nature (1906), 74, 634. 



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