1629 
observation in the microscope took place through the covering glass 
placed over the channel (not drawn in Fig. 1). 
When now the cuvette was filled with V,O, sol in suitable dilu- 
tion, | saw when closing the electric current, the particles move 
frontally througli the field of vision towards the anode. The orien- 
tation of the rod-shaped particles was unmistakable, though not 
complete. The majority lies quite frontal, but a few move about, in 
a more slanting position with deviations of about 10°, more rarely 
of about 20°. 
The orientation would, of course, be strengthened by bringing 
about a greater potential difference between the electrodes. The 
greater velocity of the motion and the rapid, complete cataphoretic 
accumulation of the particles at the anode then however, impeded 
the observation. Hence we proceeded to the alternating current 
which was furnished by a small Rumxkorrr coil such as is used 
in the determination of the electric conductivity of electrolyte solu- 
tions. For Corron and Movron *) have observed that a colloidally 
dispersed particle follows the impulses of the current and thus gets 
into vibration owing to an alternating current. Indeed, the little 
rods now orientated purely frontally and exbibited themselves as 
elongated rays of light in consequence of the after-images of the 
eye; these rays often reached from one side of the light-cone to 
the other. The field of view was much cleared up on closing the 
current, a phenomenon that may be valued in the same manner as 
indicated in § 4. 
It should be noticed that sometimes, besides the vibration a one- 
sided cataphoretie motion occurred which caused a movement, some- 
times from the left to the right, then again from the right to the 
left, occasionally even right across the field of vision. Particularly 
during the first moments after starting the inductor, such anoma- 
lies now and then occur. They correspond to the anomalies observed 
by DiesserHORsT, FREUNDLICH and LxonarpT in similar circumstances 
and are probably to be attributed to leakages in the circuit in 
connexion with the not vet stationary action of the RumKorrr coil 
when just put in action. 
6. Modified cuvette. Much more striking however, is the image 
when the cataphoresis is brought about parallel to the illuminating 
beam. For this was constructed a cuvette as shown in Fig. 2. 
It differs from the first in so far that one of the platinum elec- 
1) Journ. de Chim. phys. 4, 365 (1906). 
