Emanation in the Lower Regions of the Atmosphere. 7 



From this table we see that, if after a period of rest of 

 six days the amount of emanation accumulated is M, the 

 amount that would be accumulated in one day is 



66-0 



Throughout the experiments it was the accumulation 

 per day that was required. This amount, however, would 

 be hard to measure accurately, and to get the daily accumu- 

 lation the tubes were allowed to rest for longer periods. At 

 the end of such a period of rest, the emanation accumulated 

 was driven off by heating and the amount tested in the usual 

 way. The usual period of rest was from Friday afternoon 

 to Monday afternoon — 3 days, — so that Monday's heating 

 expelled a three days' accumulation. Table II. (p. 8) gives the 

 results obtained for this accumulation. The fifth column 

 was obtained from the third and fourth columns by using the 

 figures in Table I. as described above. 



The figures obtained for the daily accumulation of A or B 

 are not quite constant. This is inevitable from the smallness 

 of the quantity under measurement ; the agreement, however, 

 indicates that it is radium emanation that is being generated. 

 The average value of the leak due to the daily accumulation 

 works out at '46 for tube A and *48 for tube B, or approxi- 

 mately *5 for each tube. 



It was just possible that some of this accumulation might 

 be driven out by the air-stream during an " exposure/'' so 

 that from the reading of the total emanation collected from 

 the heated tubes after a day's run less than '5 should be 

 deducted. It is rather difficult to test this point accurately; 

 but experiments made by giving the tubes just an hour's 

 " exposure " showed that none of the accumulation had been 

 driven out in that time, so that perhaps all the accumulation 

 remains proof against a twenty-one hour air-stream. 



As a sample reading I will quote that of Thursday-Friday, 

 Aug. lOth-llth. 



Air-stream started through tubes at 5.14 p.m., gauges 

 checked at 8.4 a.m. next morning, again read at 2.14 p.m., 

 and current then stopped. The stream had remained practi- 

 cally at *5 litre per minute all the time, A had gone up 

 slightly, B down. The time of exposure was 1260 minutes, 

 and the gauge readings showed that 635 litres of air had 

 passed through A. and 625 litres through B. 



