the a. Particles of Radium. 

 §11. 



323 



Having made those various improvements in our apparatus, 

 and become more familiar with its use, we made a new layer, 

 as already mentioned, from the pure radium bromide which 

 Mr. Soddv had so kindly sent us. This at once gave good 

 results. The curves shown in fig. 1 show the considerable 

 precision which it was now possible to attain. 



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It may be well to repeat here that these ionization curves 

 show the amount of the ionization due to the « rays at various 

 distances from the radium layer, the medium ionized being 



