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state that the analogy with a doublerefractive erystal goes so far that 
one notices the typical axial cross when the sol is examined in 
convergent polarised light, while the liquid moves in a direction 
coinciding with the microscope-axis. 
A similar behaviour was exhibited by old Fe,O, sols. 
These experiences gave rise to interesting views as to the crystalline 
condition; they are principally of great importance for the theory 
of the liquid crystals; for the analogy with these substances is 
particularly striking. 
2. In April 1915, I prepared a not very concentrated V,O, sol. 
according to the method given by Bitz") It absolutely did not 
exhibit, on stirring, the dark diffusions, neither could I observe a 
light-phenomenon between crossed nicols either by simply placing 
them before a planeparallel cuvette or in the polarisation microscope. 
When in December I once again took the specimen in hand 
both phenomena were exhibited with manifest intensity. With this 
preparation the experiments now to be described have been made 
in January, February and March 1916. 
The object of the research was to verify the above hypothesis 
with the ultramicroscope. It appeared to me that by means of the 
microscope it could be ascertained whether, indeed, the particles in 
the circumstances indicated range themselves in the way expected. 
’ 
&, Observation in the cardioid-ultramicroscope. The specimen was 
strongly diluted to a faint yellow liquid; a drop of this was put 
into the instrument. 
Source of light: Wrure arc-lamp. Objective: Special apochromatic 
(Zeiss). Compensation ocular 18. 
The intenference images are highly peculiar: long pale blue streaks, 
certainly 20 times more in length than in width, are seen in quiet 
Brownian movement, between these, small round dises in vivid motion. 
The apparent size of the rods is about 1 cm. They are elongated 
supple particles, which move about like little serpents, bend to and 
fro and take the form | evidently under the influence of molecular 
thrusts in opposite direction near the termini. Further, V-shaped 
twin combinations are again moving more slowly, also some couplings 
of three and more rods to spiderlike complexes. 
On the slide and covering glass larger complexes have deposited 
as little flakes; therein may be still observed plainly the single rods 
1) W. Briurz, Nachr. Göttingen 1904, 8. 
