DLSCHARG-E FROM METALLIC SURFACES IN DIFFERENT GASES. 
Discussion oj Observations. 
i'lom the series ol curves given in figs. 4 and 5 certain of Stoletovv's results can 
be verified at a glance. Thus the first result given by Stoletow —that when the 
potential is kept constant and the pressure gradually decreased, the current first 
hicieases, reaches a maxinium, and then decreases towards a finite limit wliicli is 
independent of tlie potential within very wide limits—can be seen at once from fig. 4. 
The second result given by Stoletow— that at ordinary pressures tlie current 
increases slowl}-^ with the potential difference, approaching a kind of saturation which 
is more marked at low pressures—needs modification. As the pressure is lowered 
the flatter part of the current-E.M.F. curve, corresponding to approximate saturation, 
becomes steeper and steeper until at a few millimetres pressure tliere does not appear 
to be any approach to saturation, a small cliange in the potential difference producing 
a big alteration in the current, whatever tlie potential difference may be. It is only 
when the pressure is much lower than this that a further decrease in pressure 
pioduces a closer approach to saturation, until at a pressure of about a tenth of a 
millimetre, depending on the distance between the electrodes, we actually get a true 
saturation current which decreases with the pressure, approaching a finite value as 
the pressure is indehiiitely decreased. 
