Electric Discharge in rarefied Hydrogen and Oxygen. 307 

 Table XI. 



p- 



w. 



Y. 



w/p. 



Y/p. 



45 



•75 



50 



•17 



11 



21 



1-5 



40 



•7 



19 



1-05 



1-3 



25 



1-24 



24 



•65 



'85 



15 



1-3 



23 



The last two rows of the table show an interesting agree- 

 in en t of the observations with the theory advanced to explain 

 them. The fact that under certain conditions the chemical 

 .action per coulomb can be increased by lowering the pressure 

 down to a certain point, after which the chemical action is 

 diminished, is thus explained. In fact the theory enables one 

 ^completely to account for the complicated and paradoxical 

 effects observed and to interpret the forms and explain 

 the relative positions of the curves (such as those of fig. 2) 

 which give the values of Ap/AQ for the various pressures. 

 It is unfortunate that the method here pursued does not lead 

 to a oreater variety o£ results. A more elaborate apparatus 

 .and a battery of far more than 2000 volts would be necessary 

 to extend the range of observations. And even then the 

 range of force in the positive column, however accurately 

 that force might be determined, would be far too limited for 

 •the purpose in view. 



In thus accounting for the observed phenomena I have 

 assumed that only negative ions pass through the whole 

 leno-th of the positive column. But the explanation given 

 does not essentially involve that assumption. It will still 

 hold good in a slightly modified form if we suppose that 

 positive ions originating near the anode (see J. J. Thomson, 

 ' Conduction &c. 5 p. 489) traverse the positive column with 

 chemical results as well as negative ions, provided that the 

 proportion of one kind of ions to the other does not sensibly 

 change with change of pressure and electric force in the 

 positive column. In that case the equation 



p J \pJ 



is still true, only w is now the number of molecules of water 

 resulting from the dissociation effected by both kinds of 

 ions in a centimetre of the positive column. In fact these 



Z2 



