Heating Effect of Radium and its Emanation, 319 



heating effect of the tube is due to the emanation alone, 

 31 per cent, to radium A, and 40 per cent, to radium B-f 

 together. It should be mentioned that it is difficult to deduce 



Fiff. 4. 



1 



Q 

 k 



< 0-25 



1-5 



1-25 



1-0 



075 



0-5 





0-0 





















X 































































































10 



/2 »4- 16 



/tf/zvi/rss. 



with certainty the exact ratio of the heating effects due to 

 the emanation and radium A on account of small errors in 

 the determination of the lag. It is clear, however, from the 

 experiments that the heating effects are nearly equal. 



These deductions were verified by another method which 

 avoided the necessity of any correction for lag or for galvano- 

 meter or scale errors. The emanation-tube was replaced by 

 a glass tube of the same dimensions, over which was wound a 

 layer of fine insulated manganin wire whose resistance was 

 determined. The variation of the heating effect of the 

 emanation-tube after removal of the emanation was then 

 calculated from the known periods of transformation of 

 radium A, B, and C, assuming that the emanation provided 

 29 per cent, of the total, radium A, 31 per cent., radium C, 

 40 per cent The current through the resistance-coil to give 

 a corresponding heating effect was then calculated, and the 

 external resistance to be added in the battery-circuit at any 

 moment deduced. The initial amount through the coil was 

 adjusted to give nearly the same deflexion of the galvano- 

 meter as that due to the emanation. By means of a dial 

 resistance-box, the resistance could be rapidly varied to give 

 at any moment the required heating effect. For example, to 

 imitate the removal of the emanation the resistance was 



