50 
Transactions of the Boyal Society of South Africa. 
At 90° the substance is solidified : the magnetic field has no influence 
on it. These observations were made during the gradual cooling of the 
substance. 
Similar observations were made on the rotation of the axis of spherical 
crystals and crystalline solutions of Paraazoxyphenetol with a trace of 
olive oil ; on Anisaldazin with olive oil and piperin ; and also on Para- 
azoxyanisol with olive oi]. The results agree with those obtained by 
O. Lehmann.''- 
EONTGEN EaYS AND LiQUID CeYSTALS. 
Paraazoxyanisol was heated until it became amorphous. It was then 
allowed to cool gradually in a magnetic field of 5,000 Gauss. 
The object of this was to see whether the principal axes remained 
parallel to the magnetic field, or whether they changed during the process 
of solidification. If they remain fixed then the interference pattern must 
show radial lines on the films. 
After an exposure of four hours one film was removed and developed. 
It clearly showed interference phenomenon but no symmetry at all. The 
pattern obtained is similar to those of Hupka f in his experiments on 
microcrystalline substances. 
The second film was developed after an exposure of eight hours, and 
also showed the same unsymmetrical interference points on the film. 
From these results we conclude that the axes did not remain fixed 
when the substance was allowed to solidify in this magnetic field. This 
could also be seen on microscopic examination of the layers. 
Secondly, we see that such layers do cause interference phenomenon 
which is not absorbed by the glass plates. 
The same layer was then heated up to 118° in a magnetic field of 
5,000 Gauss, and carefully observed for half an hour by means of the 
microscope. The temperature was kept constant by observing the deflec- 
tion of Gi, which was kept constant by regulating the current through the 
spirals by means of E2. 
As no change was observed the microscope was removed, the cylinder 
with diaphragms placed in front of the solution, two films behind the 
solution, and the whole covered in with lead sheets. G2 was switched and 
the temperature regulated by E3. 
After an exposure of eight hours the first film was developed. It 
showed no trace of interference phenomenon. Only dispersion of the 
rays could be observed, viz. an enlargement of the central spot which is 
due to direct transmission of the rays. 
* 0. Lehmann, Phys. Zeitsch., 13, 550, 1912. 
t E. Hupka, Phys. Zeitsch., 14, 623, 1913, fig. 3. 
