STUDIES IN DETKCTING RAIMO-ACTIVE FALL-OU'l' 



occur simultaneously in both i>raphs [Figure 2). Actually, when viewed 

 broadly, as on ilu- graph with a smaller scale, these differences become far 

 less important, and peaks can be seen with relative ease. 



500 



250 





 IjOOO 



AlkJ 



I/) 



m 500 



O) 



c 

 c 



D 



o 

 u 





 30.000 



20,000 



10,000 



1,000 



500 



Cheesecloth 



'Fall-out' dust 



Rainwater 



— Counts/minute/litre 



— Counts /mmute/weekly 

 rainfall 



June 



Dec 



June 



1957 



1958 



Figure 2. Activities of cheesecloth, 'fall-out' and rainwater 

 samples in 1957 and 1958 



The normal counting rate for 1 litre of water was 6 counts per min above 

 background, and peaks regarded as significant occurred : 



on the 24th October, 1957 — 1000 counts/min were recorded, 

 and in July and August, 1958 — 12 counts/min were recorded. 



In comparing the weekly activities collected with cheesecloth, dust 

 collected from the roof, and rainwater, we find that there is a good agreement 

 in the main peaks. Since the fall-out and water collections were not com- 

 menced until a couple of months after the cheesecloth collection, no com- 

 parison can be made for the 6th June, 1957, but we see that on 24th October, 

 1957 a peak is recorded in each case and also a general increase in activity 

 in July and August, 1958. 



130 



