695 
One of the registered lines is reproduced in Fig. 1°). 
The following pecularities are to be noticed with regard to this 
Fig. 1. 
line. On the lefthand side the line is horizontal and straight’). This 
means that the temperature was constant at the beginning of the 
observation. This constant temperature prevailed in the liquid which 
at first surrounded the thermo-element, and was equal to the tem- 
perature of the thermostat. The boundary of the solid phase was 
still too far off to heat the surroundings of the thermo-element 
through the heat of fusion liberated there. When the solid phase 
approaches the thermo-element, the temperature begins to rise, and 
the curve presents an ascending branch. When the boundary plane 
of the solid and the liquid phase has reached the thermo-element, 
the temperature is maximum; the curve presents a sharp point. 
Then the temperature is seen to fall again, and finally it reaches 
again a constant value on the righthand side of the figure, viz. the 
temperature of the thermostat. In this last stage of the process, the 
thermo-element is in the solid substance, and the surface of the 
phases is so far distant that the generation of heat taking place 
there, has no influence then. 
In this curve the maximum is of the greatest importance. It 
indicates the temperature of the boundary between the two phases. 
This temperature determines the velocity with which the boundary 
moves in the direction of the solid substance towards the liquid. 
The relation between the temperature at the boundary of the phases 
and the linear velocity of crystallisation depends on the nature of the 
1) The curve of fig. 1 was registered in 9 minutes. 
®) The break in the horizontal line is caused by a constant electromotive force, 
which enables us in the way described on p. 694 to find the temperature from 
the deviation of the galvanometer. 
