1423 
“The application of the data obtained at temperatures below the 
vanishing point is in the nature of the matter uncertain, as we do 
not know whether, with the galvanic change in the mercury, there 
may not be another change in the thread, which would bring about 
a further change in the giving off of heat. 
With regard to the appearance of potential differences at the extre- 
mities of the thread, we found the data contained in Table V. 
At 3°.6K. the current at which a potential difference would 
appear in the sentinel wires could not be measured, as, before the 
>" 
oA. Be By EB V. 
Strength of current at which the potential 
difference appears at the extremities of a mercury | 
wire carrying a current below 4°.2 K. 
mr2 = 0,0025 mm? for C. 
Temp. ee B ¢ 
4°.18 K 0,0535 0,0615 0,034 
4. 10 0,232 0,317 | 0,172 
3. 60 | | 1.068 
3. 28 1,646 
2. 45 | 2,56 
current had reached this value, the resistance C was heated to above 
the vanishing point along too great a length. 
What we were aiming at was however attained in these experi- 
ments of Feb. 1912. It is established that heat is produced in C by 
raising the strength of current sufficiently, and that the heat is not 
conducted to it from A and B, since A and B were at a lower 
temp. than the vanishing point as appeared by the absence of poten- 
tial fall in them. It is developed in the thread itself. 
Table VI may be subjoined concerning the experiment at 2°.45 K. 
corresponding to Tables I and III. 
At the same moment that the galvanometer which measures the 
potential difference at the extremities of the thread is deflected, the 
strength of current in the main circuit falls from 7 = 2.84 amp. 
to 21.04 amp. which corresponds to an increase of resistance 
A W = 2.44 2 in the circuit, from which it appears that the resistance 
is heated nearly to the temperature of hydrogen by the remaining 
current, of 1 amp. nearly. 
