OF FLAMES CONTAINING SALT VAPOURS. 
505 
In this case, in which the positive or lower electrode is hotter than the negative 
electrode, the current does not show much sign of arriving at a saturation value as 
the E.M.F. is increased. To see whether this depends on the relative positions of the 
electrodes with reference to the direction of motion of the flame gases, the lower elec¬ 
trode was flxed very near the base of the flame, so that it was less heated than the 
upper electrode. It was then found that when the lower electrode was positive, the 
current became nearly saturated with about 100 cells, whereas when the lower elec¬ 
trode was negative, the current showed no sign of attaining a saturation value. 
Thus the saturation of the current depends on the temperatures of the electrodes, 
and not on the motion of the flame gases. 
Diagram No. 5 shows the relation between the current and E.M.F, when the 
distance between the electrodes was 0’3 centim., the lower electrode being slightly 
hotter than the upper electrode. 
Diagram No. 5. 
When the E.M.F, is less than 150 volts the two curves are similar to those 
obtained when the electrodes were at greater distances apart, but at higher E.M.F.’s 
the current with the lower electrode positive increases rajDidly with the E.M.F., and 
becomes greater than that with the lower electrode negative. In all these experiments 
except those in which the upper electrode was heated by an electric current, the 
heated surface on the upper electrode was considerably greater than that on the 
lower electrode, owing to the upper electrode being of finer gauze than the lower 
electrode, but the lower electrode was usually heated to a higher temperature than 
VOL. CXCIl.-A. 3 T 
