On the SiMce-lattice of Liquid Crystals. 
47 
The Appabatus. 
In order to heat the substance to a fixed temperature a pair of copper 
spirals were constructed out of two copper cyhnders and four copper 
cylinders. 
As these substances had to be placed in a magnetic field equal lengths 
of copper wire were wound round the coils, so that the current passed in 
opposite directions round them. This avoided the turning moment of the 
magnetic field on the spirals (Fig. 1). 
Fig. 1. 
BA. The layer of liquid crystals between the glass plates. J mm. thick. 
C. Clamping screw. 
Between these spirals the substance experimented on is enclosed 
between two thin glass plates, which are kept in position by means of 
three screws which clamp the spirals together. 
The temperature of the substance between the glass plates was deter- 
mined by means of a sensitive thermocouple, whose junction just touched 
the glass plates. 
The object of the thermocouple is more to keep the temperature 
constant than to measure its actual value. 
