400 



Reports on Special Researches 



Almospherie-Electric Observations: Radioactive Content 



(Form 103) 



In the above observations on the radioactive content of the atmosphere, the times 

 at which the fiber crosses the fixed marks are recorded in columns 1-20. In exceptional 

 cases, where a large amount of active material is collected, one can, in a short time, make 

 several determinations of the quantity t. In such cases it is possible to group the observa- 

 tions in columns 1-20 about certain mean times, so that several of the observations may 

 have their share in the determination of each point of the curve actually drawn for 77. 

 For this purpose is employed the table headed "Means corresponding to a single point of 

 the decay curve." In general, however, as in the example cited, the amount of active 

 material collected is so small that it is not possible to adopt this scheme, and the intervals 

 r„ recorded are the same as the intervals t. 



