Electric Wind in Hydrogen containing traces of Oxygen. 457 



negative. It is therefore much more likely that the high 

 temperatures in question are due to increase in the back 

 discharge rather than to any change in V — • 



c . 



There remains one other point to be referred to — the 

 curious shifting of the negative wind-pressure curve parallel 

 to itself — an effect which was first observed in the 1901 

 experiments. 



In the present work it has been again met with, and now 

 turns out to be another of the effects which a small amount 

 of oxygen has the property of destroying. An examination 

 of the wind-pressure curves themselves will make the matter 

 clearer. 



Curves II. 



In Curves II. are given typical wind-pressure curves for 

 positive and negative discharge, and a current of 2 micro- 

 amperes in hydrogen containing various percentages of 

 oxygen. The wind pressures for different distances, z, 

 between point and plate are here plotted with z, the origin 

 corresponding with the position of the plate. As it is the 



