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NOTE ON THE MOLECULES OF LIQUID CEYSTALS. 
By J. Steph. van der Lingen. 
In an earlier communication it was shown that pseudo-isotropic layers 
of certain liquid crystalline substances have no space-lattice in spite of 
the fact that such layers showed the same optical properties as uniaxial 
crystals cut perpendicular to their optic axis. When the substance is 
placed between glass plates then the arrangement of the molecules is 
probably as indicated as in Fig. la where the layer is not thin. That 
is, only the molecules near the surfaces of the glass are parallel to the 
glass; those farther off are not affected by the glass plates. In Fig. lb 
all the molecules are parallel to the glass plates. In this case all the 
principal axes of the molecules are perpendicular to the plates. Such 
layers behave (optically) like uniaxial crystals cut perpendicular to the 
optic axis. 
Fig. la. Fig. 16. 
If a thin layer be placed in a magnetic field, then the molecules near 
the surface of the plates will not be completely orientated on account of 
the influence of the glass plates, which is at right angles to the magnetic 
force. In thicker layers the majority of the molecules will be perfectly 
orientated by magnetic fields : the unorientated portion being neghgible in 
comparison with the orientated portion. 
In strong magnetic fields the planes of the molecules are perpendicular 
to the lines of force, hence in the experiments on pseudo-isotropic layers 
the rays passed perpendicularly to the optic, i.e. magnetic, axis of the 
molecules. (See Fig. 2.) 
If the molecules themselves are crystals then photogram of their 
space-lattice cannot be obtained in this way on account of the fact that 
there is always a possible translation of the molecules, and more espe- 
