70 THE BUREAU OF SCIENCE 



The variation of all of the above factors with the changes in 

 the meteorological conditions is being made the especial point 

 of investigation. Up to the present time simultaneous observa- 

 tions on all the different phases of the problem have never been 

 attempted at any one laboratory, although frequently suggested 

 as necessary. 



Observations on the radium-emanation content of the atmos- 

 phere have been taken during the last year by two widely differ- 

 ent methods. The first method, which is the one best adapted to 

 the purpose, is the absorption of the emanation by charcoal made 

 from the shells of coconuts and the direct comparison of the 

 amount collected with that given off in a given time from a 

 known amount of radium bromide. The other method, which 

 is especially adapted to a study of the hourly variations of the 

 emanation in the air, involves the collection on a negatively 

 charged wire of the radioactive products of the emanation. 



The data obtained from observations extending over a period 

 of about sixteen months show that the radium emanation con- 

 tained in the lower regions of the atmosphere per cubic meter 

 is of the same order of magnitude as that found for Cambridge, 

 England, and slightly greater than that for Montreal, Canada, 

 being equivalent to that which would be in radioactive equilib- 

 rium with about 103 X 10-^- grams of radium. Observations 

 by the radioactive deposit method have shown a diurnal varia- 

 tion with a decided minimum in the evening and a maximum 

 in the early morning. 



During the months of April and May, observations by the 

 absorption method were taken at Pauai, Benguet subprovince, 

 elevation 2,456 meters (8,060 feet), by Doctor Wright and Mr. 

 Smith, for the purpose of determining the variation of the 

 amount of emanation with altitude. The average amount of 

 emanation per cubic meter was found to be equivalent to 

 that which would be in radioactive equilibrium with about 

 24 X 10~^^ grams of radium, as compared with 103 X 10"^^ 

 for Manila. 



Work on the other above-mentioned factors entering into the 

 electrification of the atmosphere is now under way, with the 

 especial object in view of determining for a period of at least 

 one year the relation existing between them and the changes 

 in meteorologic conditions. 



