Heating Effect of Radium and its Emanation. 315 



The current through the platinum coils never exceeded 

 1/100 ampere, and was generally abont 1/200 ampere. 



A calibration of! the scale of the galvanometer was made 

 by placing a heating-coil of small dimensions of covered 

 manganin wire within one of the platinum coils, and noting 

 the steady deflexion when known currents were sent through it. 



JFiar. 1. 



P 



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 • I 



A 



It was found that the deflexion of the galvanometer from the 

 balance zero was very nearly proportional to the heating effect 

 of the manganin coil, for the range of deflexion employed, 

 viz. 400 scale-divisions. The deflexion thus served as a direct 

 -measure of the heating effect. 



Y2 



