of Instability of Electrified Drops, etc. 73 
position; but the current may be maintained at a lower voltage 
than that at which it began. 
__ 4, A water surface in carbonic acid at atmospheric pressure 
shows the same behaviour at the lower potentials as that described 
‘in § 2 when air was used, but as the voltage is raised the blurred 
‘meniscus suddenly changes in this case not to a distinct hemi- 
‘spherical form as before but into a steady cone with a faint dark 
‘line extending outward from the apex for some distance, as shown 
by the drawing “a” in Fig. 2. 
a 
i 
Fig, 2. 
The height of the cone changes with change in the liquid 
pressure and when this is diminished sufficiently the form becomes 
that shown at “b” in the figure, where the small pointed portion 
at one side is to be noted as well as the faint dark streak extending 
out from it: The cone-shaped meniscus persists over a rather 
Marrow range of voltages, and when the upper limit of this range 
is reached the surface again becomes agitated. 
5. The potential at which the current ceases from a water 
Bertece in carbonic acid was found to be almost if not exactly 
identical with that at which the current ceases from the same 
point in air. Carbonic acid, however, shows the unique behaviour 
that this voltage remains unchanged for pressures down to about 
‘one-third of an atmosphere, below which pressure the intermittent 
‘stage of the current disappeared. The conical meniscus was not 
‘obtainable for pressures much below the atmospheric pressure. 
6. In hydrogen no intermittent stage of the current was 
‘observed with a water surface whatever the pressure of the gas 
(below an atmosphere). The current begins suddenly with a 
considerable magnitude, as described in § 3 for air at reduced 
pressures. 
