lating with the average section of the tube in which the thread is 
frozen, only a lower limit can be given for this. 
Possibly the mercury in A and B was only frozen in an unfa- 
vourable form, and therefore greater local current densifies or worse 
exchange of heat had arisen than the average. 
§ 7. Repetition of the experiment with the same apparatus. We 
obtained more favourable results from another freezing.. First a few 
results may be given, which were obtained by measurements at 
different strengths of current at 4°.25 K., that is at a temperature 
above the vanishing point. These results gave an opportunity of 
judging to what degree heat can be given off by the mercury thread 
closed up in a glass capillary or flows off along the extremities. 
From the increase of resistance at greater current strength, the 
rise of temperature was deduced on somewhat simplified suppo- 
sitions, at which the equilibrium between the Joure heat and the 
heat given off to the outside is established. The result for the resis- 
tance and the average rise of temperature of C was: 
current resistance rise of temp. 
0,006 amp 0,1928 Lif 
OOB EES 0,1932 0°, 
0358 |); 0,2149 012 
0500 + Sy 0,2410 0°25 
The average rise of temperature was calculated by the formula 
got by separate determinations 
Wr= Ws + 0.9(T — T,))*) 
in which 7, represents the boiling point of helium. 
It follows from these determinations that per degree of difference 
of temperature between mercury thread and bath 0.057 calorie is 
given off per second. If we assume that all the heat goes through 
the glass, that the mercury touches the glass everywhere, and that 
we only have to consider the narrow capillary, then we find with 
d; = 0.056 mm, d= 2.07 mm, 7100 em, for tbe conductivity of 
glass & = 0.00033, while at ordinary temperature £ = 0.0022. 
The loss of heat through the glass must therefore by cooling to 
the boiling point of helium have become much less than at ordinary 
temperature, which might possibly be the consequence of the mercury 
only touching the glass at a few places besides in the bends. 
1) See the fig. in Comm. No. 124. Dec. 1911. 
