181 



of these experiments, given in table iii. and shown by the 

 dotted curves in fig. viii. show that this anticipation was 

 realized. 



The dotted curves ' j^y j and ' Zn' ) iieed not be consid- 

 ered at present; they were obtained with a carbon floor in- 

 troduced into the ionization chamber. 



Al, C, Zn, Fe, S, and Sn give results which are all very 

 nearly identical, and the curves show a considerable differ- 

 ence in slope to what they did in the previous experiment. 



Pb and Hg, however, are distinctly dift'erent from the 

 other substances, of which we may hereafter take Zn as typi- 

 cal. 



The curve for Pb has not been altered to such a large 

 extent by the change of arrangement of the experiment as 

 has that for Zn and such substances. 



