Vapour from electrified Still Surfaces of Liquids. 221 
tained the liquid to be evaporated, rested upon wire netting 
over the flame of a spirit-lamp. A platinum wire, connected 
with one pole of a galvanic battery, terminated in the liquid of 
the flask. The other battery-pole was connected with the 
earth. Close over the mouth of the flask was a strip of 
platinum, so placed as to be directly exposed to the action of 
the rising vapour. This strip could be connected either with 
the upper condenser-plate or with the earth, according to the 
arrangement of the experiment. The lower condenser-plate 
was fastened upon a very sensitive pile-electroscope. As soon 
as the water began to boil, or even approached boiling, and the 
under condenser-plate was connected with the earth, then the 
upper plate collected electricity of the same kind as that of 
the pole which stood in connexion with the water. A single 
pair of Bunsens was sufficient to noticeably separate the 
gold leaves of the Bennett electrometer. The charge increased 
proportionately with the number of pairs employed. The con- 
denser remained closed one minute each time. If the liquid 
was in rapid ebullition, this length of time was not necessary 
for the charge to reach its maximum." 
Against this method of arrangement of the experiment, 
which coincides in many of its principal points with the above 
described, arises the objection that convection of the electricity 
occurred, not by means of the vapour, but by the drops of water 
thrown up against the platinum strip during the ebullition. 
Further, I have found during the experiment, that when- 
ever a flame touched the porcelain dish (as it was allowed to do 
in Buff's experiments) a large deflection of the electrometer- 
needle occurred. This is to be explained only through a 
convection of electricity by means of the hot gases arising from 
the flame, because the deflections began immediately when the 
increase of temperature of the liquid was so slight that there 
was no practical increase of evaporation. 
(d) By means of a modification of the apparatus described 
upon pages 217 & 218, proof of the accuracy of the results so far 
obtained by me was established by the most incontrovertible 
method of experiment possible to be devised. In place of the 
condensing-disk C, a brass ball of 20 millim. diameter was 
substituted. The arrangement of the experiment was not 
otherwise changed. This ball was placed over the still surface 
of the electrified liquid, as closely as possible without the 
passage of a spark between them ; consequently the distance 
between the ball and the surface of the liquid barely exceeded 
the striking-distance. The liquid was then electrified by 
means of a Topler electrical machine, driven with great regu- 
larity by a small water-motor, so that thus the potential of the 
