1011 
The condenser consisted of 2 square brass plates placed horizontally. 
I have worked with 2 different condensers C, and C, of the 
following dimensions : 
C, C, 
sides of the plates 20 mm. 14 mm. 
thickness De Sui, 
distance about 5 ee Bit 
C, has been used most. 
I observed through a microscope placed horizontally. A micrometer 
was adjusted between the two lenses of the eye-piece. It consisted 
of two sets of lines drawn normal to each other, 0.1 mm. apart. 
The magnification with respect to this micrometer amounted to from 
4 to 5, the total magnification to from 80 to 100. 
For the lumination I used first an are lamp of 8 amp., later 
a so-called reductor lamp. This lamp burns 14 volt and has a very 
small incandescent body, hence a very great brightness per unit of 
area. I worked with a lamp of 100 candles. 
The electric circuit was arranged in such a way that of one and 
the same particle I could successively measure the movement under 
influence of a constant force and of an alternating force. Fig. 2 sche- 
matically represents the course of the electric current. By reversing 
the double-pole  double-throw 
switch O,, I could successively 
insert the condenser C into the 
continuous-current circuitand into 
the alternate-current circuit. In 
the fig. the two condenser plates 
are in eonnection with the points 
M and N of the adjustable resi- 
stances Wy,_3,. which short- 
circuit the battery G. B,is an 
alternate-current voltmeter. By 
opening S, and throwing over 
O,, C was brought into con- 
nection with the poles of the 
secondary winding of the trans- 
formator 7, which converted the 
110 volt of the municipal elec- 
trie current supply to + 2000 
volt. B, is a voltmeter of Braun, 
Fig. 2. L is a lamp resistance. WV, and 
V, are lequid resistances, S, and S, breakers of the current, 
