506 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Fig. 27. 
Potential at the centre and 
periphery of a ring negative terminal. 
Everyone familiar with the appearance of a stratified discharge will have noticed, 
when the negative terminal is a ring, that as the exhaust proceeds a spindle of light 
approaches and at last protrudes through the interior of it, as shown in fig. 28, 5. 
This spindle is thus a visible exponent of strong action among the molecules of the 
gas composing it, and it appeared to be of interest to probe its electrical condition. We 
thereiore prepared a tube, No. 363, for this special object with an idle wire, surrounded 
by a minute glass tube, except its extremity, in the axis of the tube and projecting to 
a distance of f- of an inch (0'95 centim.) from the plane of the ring which was made 
negative. 
