84 
LUMMER. 
In the second vertical column are given the absolute tem- 
peratures, T, based on the standard work of IIolborn and 
Day, who compared the thermoelement of Le Chatelier 
with the nitrogen thermometer. The third column contains 
the radiant energy measured with a bolometer and reduced to 
the same scale at the corresponding temperatures, T, It is 
equal to zero, if the temperature of the black body equals 
that of the bolometer, which was 17° C. — 290° Abs. There- 
fore, if the Stefan-Boltzmann law is to be satisfied, we must 
have : 
where A is the reduced deflection of the galvanometer-bolo- 
meter at the absolute temperature, T, of the black body. 
The constant C multiplied by I0 10 is given in the fourth col- 
umn, from which we see how exactly the law is satisfied. We 
get a better criterion of this agreement by calculating the 
temperature, T, using for (7 the mean value 123.8, and put- 
ting it into the equation 
A = 123.8 X 10 10 (T 4 — 290 4 ). 
Thus we get the calculated values of T given in the fifth 
column. Our observations show how closelv the black radia- 
tion varies as the fourth power of the absolute temperature. 
Supposing this law to be correct with reference to the 
black body and supposing our sources to give true black 
radiation, we can correct the earlier scale of temperature es- 
tablished by Wien and IIolborn. According to this scale, 
based on the air-thermometer, our results showed a certain 
regular deviation from the Stefan-Boltzmann law. We were 
confident enough, or, may I better say, daring enough, to 
assume the temperature scale to be incorrect. And so it was! 
In an excellent research, IIolborn and Day repeated the 
very difficult comparison of the thermoelement and the 
gas thermometer, using nitrogen instead of air, and their 
new scale agreed with our observations of the fourth-power 
