On the Space-lattice of Liquid Crystals. 
49 
The electrical connections were according to Fig. 2. The galvano- 
meter G2 and resistance E3 were placed in an adjoining room in order to 
protect the experimenter from the rays, and yet enable him to regulate 
the temperatm-e of the solution. 
Method of Experiment. 
The field strengths of the electromagnets, when the spirals are between 
the poles, was determined by means of a standard Bismuth spiral. These 
were recorded for various readings of Ai. 
Next the deflections of Gi and G2 were recorded for various tempera- 
tures after the thermocouple had been standardized. 
A rubber ring of 1 cm. diameter was cut at a point and then placed on 
a clean glass plate-object ; cover slides 0-17 mm. thick and 18 mm. square 
were used. A small quantity of the substance is then carefully powdered 
and placed inside the ring, and covered with a similar glass plate. The 
whole is then carefully placed between the spirals so that the cut in the 
ring is uppermost. The junction of the thermocouple is then placed in 
position. The spirals are then placed between the pole pieces of the 
electromagnet and clamped in position. The microscope is focused on 
the substance. The substance is then heated by passing a current through 
the coils of the spiral. On melting air-bubbles are expelled through the 
opening in the rubber ring by gently screwing and unscrewing the spirals. 
Observations on a layer of J mm. thick of Paraazoxyanisol gave the 
following results : — 
This substance, which was not chemically pure, became amorphous at 
124°. The magnetic field has no visible influence on it. At 122° crystal- 
line drops commence to appear. These flow together, and soon fill the 
whole field of vision with a crystalline solution. When the magnetic field 
is put on the axes of these spherical liquid crystals all turn in one direc- 
tion, so that they become parallel to a fixed direction. The crystalline 
solution, when the magnetic field is ofl", appears like a network of dark 
stripes which move about. When the magnetic field is put on they 
disappear rapidly. The solution then appears to have the same effects 
optically as a crystal cut perpendicular to its axis. This can be seen by 
means of the Nicols which are in front of and behind this crystalline layer. 
At 118° the stripes become broader and shaded at their sides ; these 
vanish rapidly when a field of 3,000 Gauss is put on. 
At 104° the stripes only disappear slowly in a field of 5,000 Gauss. 
At 92° the substance begins to solidify. The magnetic then has only 
a partial effect on the substance. It appears as if the crystals are then 
plastic. The edges only show a slight change in colour when a strong 
magnetic field is put on. 
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