1418 
disappearance of the resistance begins, this ratio remained unchanged 
according to the observations with the differential galvanometer ; 
from that point downwards the resistance in which the current 
density was smaller, disappeared more quickly. 
Although the resistance in the experiments disappeared gradually, 
yet the way in which it disappears gives the impression that the 
change in resistance of the mercury with the temperature occurs 
suddenly and that the gradual disappearance of the potential is due 
to the fact that the thread is only gradually cooled over its whole 
length to below the vanishing point, and only that part which is 
below this temperature loses its resistance. 
It was again confirmed that at temperatures some tenths of a degree 
TABLE II. 
| 
Resistance of mercury threads carrying) 
current in the neighbourhood of 4°.2 K. 
T 3:Tamp,|mm? 1.6amp, mm? 
| 130 | 50 
| | 
49.24 K. | 0.0532 | 0.024 
4.22 | 459 | 182 
216 314 | 0.0069 
| = om 264 | 34 
} 213 | 190 13 
| 210 | 128 0.0003 
| 207 |_0.0087 | 1 
| 205 | 50 | ES 
ree 46 0.0000 | 
196 21 | 0.0000 | 
| 190 0.0005 | 0.0000 | 
180 0.0000 0.0000 | 
below the vanishing point no resistance was found up to very 
high current densities. Table HI may be compared with Table I. 
In Wiss the current density could be raised to 400 amp. per sq. mm. 
without the least resistance being perceptible. The highest limit 
for the resistance is hereby put back at 3°.6 K. to <410-!0 of 
