( 1275 ) 
cation N°. 119 a formula was deduced for the resistance of solid 
mercury ; this formula was based upon the idea of resistance vibra- 
tors, and a suitable frequency rv was ascribed to the vibrators wich 
makes @»v = a= 30 (8 = Puanck’s number 4.864 « 10 **). From 
this it was concluded : 
1. That the resistance of pure mercury would be found to be 
much smaller at the boiling point of helium than at hydrogen tempe- 
ratures, although its accurate quantitative determination would still 
be obtainable by experiment; 2. that the resistance at that stage 
would not vet be independent of the temperature, and 3. that at 
very low temperatures such as could be obtained by helium evaporating 
under reduced pressure the resistance would, within the limits of 
experimental accuracy, become zero. 
Experiment has completely confirmed this forecast. While the resist- 
ance at 13°.9 K is still 0.034 times the resistance of solid mercury 
extrapolated to O°C. at 4°.3 K, it is only 0.0013, while at 3° K it 
falls to less than 0.0001. 
The fact, experimentally established, that a pure metal can be 
brought to such a condition that its electrical resistance becomes zero, 
or at least differs inappreciably from that value, is certainly of itself 
of the highest importance. The confirmation of my forecast’) of this 
behaviour affords strong support to the opinion to which I had been 
led that the resistance of pure metals (at least of platinum, gold, 
mercury, and such like) is a function of the PraNcK vibrators in a 
state of radiation equilibrium. (Such vibrators were applied by 
EINSTEIN to the theory of the specific heats of solid substances, and 
by Nernst to the specific heats of gases). 
With regard to the value of the frequency of the resistance vibrators 
assumed before (one could try to obtain frequencies from resistances) 
it is certainly worth noting that the wave-length in vacuo which 
corresponds with the period of the mercury resistance vibrators 
is about 0.5 mm., while Rupens has just found that a mercury lamp 
emits vibrations of very long wave-length of about 0.5 mm. In this 
Way a connection is unexpectedly revealed between the change with 
the temperature of the electrical resistance of metals and their long 
wave emission. 
The results just given for the resistance of mercury are, since they 
are founded upon a single experiment, communicated with all reserve. 
1) In connection with its deduction it is to be noted that the gold-silver thermo- 
element behaved in liquid helium quite so as the experiments in liquid hydrogen 
(KAMERLINGH ONNEs and Gray, Gomm. N°, 1075) made expect. 
