Manchester Memoirs, Vol. liii. (1909), No. t. 3 



current through the coil G the central portion of the tube 

 T, and therefore the rod A, could be brought to any 

 desired temperature which was recorded by a platinum 

 platinum-rhodium thermocouple situated near A (not 

 shown in the figure). To prevent the rubber stoppers 

 D and F from burning when the tube T was heated, 

 water-coolers VV were attached to ends of the tube T. 

 The rod A was made so short, compared with the length 

 of the iron tube, that its temperature was always sensibly 

 uniform. 



To make an experiment the tube T was heated to the 

 required temperature and exhausted by a water pump. 

 A known quantity of emanation was then admitted 

 through the stop-cock K and the pressure adjusted to 

 atmospheric* After an exposure of ten minutes the 

 rod A was removed and the a radiation coming from it 

 tested in the usual way by a quadrant electrometer. 

 The results obtained will be apparent from Ftg: 2 in 

 which the decay curves of the active deposit on the nickel 

 rod at different temperatures are drawn. 



The six curves given represent respectively the rate 

 of decay of the activity collected on the nickel rod when 

 maintained at 15° C, 710° C, 840° C, 885° C, 925° C, and 

 990° C. The first curve for 15° C. exhibits the usual 

 characteristics of the a ray decay curves of the active 

 deposit for a short time of exposure. The second curve 

 shows the nature of the decay curve when the temperature 

 of the rod is kept at 710° C. during the exposure to the 

 emanation. It will be seen that the initial fall of activity 

 due to the decay of radium A is still present, but the 



* Previously lo admitting into the iron tube, the emanation was 

 exposed for about a minute to a strong electric field to remove any active 

 deposit with which it might be associated. In this way the conditions of 

 the experiments were rendered definite. 



