1316 
temperature, up to above the second point of transition may be attained. 
In the middle of the strip between the coils a circular pole appears, 
the edge of which carries a round piece of glass, a second piece 
of glass lying on top of it with a ring of paper between them. The 
substance is put in the space between the two glasses and the ring. 
_ TO THERMOPILE 
~ FROM NERNST- BURNER 
Fig. 1. 
By the aid of two small mirrors a beam of light is sent through 
the substance from aside. During our measurements the small oven 
was placed horizontally between the poles M, and M, of a Dvsots 
magnet. This magnet is fixed on a stand that allows a rotation 
round an axis lying in the direction of AA. Therefore, when the 
poles are placed as shown in fig. 1, the field of forces will be 
in a perpendicular position, parallel to the rays of light which 
penetrate the substance. 
When the magnet is rotated 90° the lines of force are horizontal 
and will cross the rays of light perpendicularly. 
A Nernst-burner connected to a battery of accumulators produces 
the required light. On the thermopile an image of the Nernst- 
burner is formed by a hollow mirror. The rays of light on this way 
from the hollow mirror to the thermopile penetrate the substance. 
The slit in the thermopile has the same RE as the image 
of the Nernst-burner. 
In the liquid-erystalline condition the diit of the matter 
confuses the image proportionally to the opacity. So the intensity of 
the thermocurrent gives us a measure for the extinction. 
The galvanometer records were registered. 
$ 2. The measurements. 
It had appeared to us that the changes in the extinction caused, 
by the magnetic field often persisted. So it became advisable to 
