440 
PROFESSOR C. H. LEES: THERMAL AND ELECTRICAL 
Hence 
l-/Kt = I (a/ef. 
The value of e, the charge on an electron, is known with a fair degree of accuracy 
to be lTxlO -20 electromagnetic units, # but the value of a is still uncertain, 
as it depends on the number n of molecules in a cubic centimetre of a gas 
(a = 3 . pressure/2n abs. temp.). The following table gives a few of the values which 
have been found for n by various methods and the values of a and of /’/ kI calculated 
from them :— 
Author. 
Method. 
n. 
a. 
k/Kt. 
Kelvin! .... 
Viscosity of gas and density when 
1 x 10 20 
5‘6 x 1CP 17 
3•3 x10~ 9 
condensed 
- Kelvin t .... 
Effect of atmosphere on light . 
>2-4 x 10 19 
< 2 • 3 x KT 16 
<5-9 x 10 -s 
Jeans§ . ... 
Viscosity of gas and Van der 
Waals’ b 
4 - 6 x 10 19 
1-2 x KT 16 
1-6 x10-s 
Planck|| .... 
Radiation theory and entropy . . 
2-8 x 10 19 
2-0 x lO” 16 
4-3x 10-s 
LorentzII . . . 
Radiation theory. 
— 
1 - 2 x l(r 16 
1 • 6 x10~ 8 
J. J. Thomson* * * § ** \ 
f Determination of e and assump-1 
< tion that atom of H in > 
4 x 10 19 
1 • 4 x 1CT 19 
2-2 x 1CT 8 
H. A. WlLSONTT J 
L electrolysis carries charge e . J 
f! Ditto, but assuming charge on 
2 x 10 19 
2-8 x lO" 19 
8-7 x 10- s 
H atom to be 2e 
From this it appears that we are not yet in a position to calculate more than the 
order of magnitude of the constant f («/<?) 2 which the electronic theories give as the 
value of k/Kt. 
In order to see how far the theoretical result agrees in other respects with the 
observed facts, the values of k/Kt at various temperatures for the metals and alloys 
tested have been calculated from the values of the thermal and electric conductivities 
given in the tables on pp. 426 and 437. The results are shown in the following table 
and in the curves on Plate 31. 
The corresponding values calculated from Jager and Diesselhorst’s experiments 
at 18° C. and 100° C. are also given for comparison. 
* The mean of J. S. Townsend’s (‘ Phil. Mag.,’ 45, p. 133 (1898)), J. J. Thomson’s (‘ Phil. Mag.,’ V., 
p. 355 (1903)), and H. A. Wilson’s results (‘Phil. Mag.,’ V., p. 441 (1903)). 
t Kelvin, ‘Phil. Mag.,’ 4, p. 197 (1902). 
t Kelvin, ‘Phil. Mag.,’ 4, p. 301 (1902). 
§ J. H. Jeans, ‘Phil. Mag.,’ 8, p. 694 (1904). 
|| M. Planck, ‘Ann. der Phys.,’ 4, p. 566 (1901). 
II H. A. Lorentz, ‘ Versl. Akad. van Wet.,’ 14, p. 518, &c. (1906). 
** J. J. Thomson, ‘Phil. Mag.,’ 5, p. 355 (1903). 
ft H. A. Wilson, ‘Phil. Mag.,’ 5, p. 441 (1903). 
+ + This line is added since Professor Townsend’s jiroof that when a gas is ionised by Rontgen rays 
there are only half so many positive as negative ions produced (‘Proc. Roy. Soc.,’ 80, p. 210, 1908), seems 
to render it advisable to take into account the possibility of the H atom in electrolysis having a charge 2e. 
