404 
PROFESSOR C. H. LEES: THERMAL AND ELECTRICAL 
Thus 
j = 1 f 0 '2406A [(1 — 0'057A) P ft -(0'021. + Q-Q0011t) A] 
10-90 | (1-020 + 29/;) 102-35 (R B -R T ) 
0-000018 
J 
i.e., 
h = 0-0003 UA (1-°- 0 5 7A ) p »-(0-021+0-00 0 l 1 r)A 
(1-026 + 29A) (R b -R t ) 
■o-oooooio. 
The table on p. 405 gives the observations and their reduction. 
Although the determination of the general law of variation of the coefficient h with 
temperature is not necessary for the purpose of the present work, it may be of 
interest to point out that the observed values of h for the three values of the mean 
temperature of rod and enclosure measured on the hydrogen temperature scale do not 
agree with any of the formulae which have been proposed to express that variat ion. 
Lorenz^ proposed the formula h cel+bt Vi , but Wagner"! has recently found it 
unsuitable and suggests h cc 1 + bt 2 , while I found j h cc t n , where n — 0'26, suitable over 
a comparatively small range of temperature. The present observations suggest the 
expression It cc 1 + bC 2 for the case of a small rod at very low temperatures in an 
enclosure only a few, say 10, degrees cooler than itself, t is the mean temperature 
of rod and enclosure on the hydrogen thermometer scale. 
Results of Thermal Conductivity Experiments. 
In the Tables of Observations and Results which follow, the values of the quantities 
observed are given after correction for errors, if any, of the observing instruments. 
In addition, a few of the most important quantities involved in the calculation of the 
conductivities are given, in order to facilitate comparison of the different experiments 
with each other, and to enable errors in the calculations to be more readily detected. 
* L. Lorenz, ‘Ann. der Physik,’ 13, p. 582 (1881). 
t R. Wagner, ‘ Beiblatter,’ 27, p. 534 (1903). 
t C. H. Lees, ‘Phil. Mag.,’ 28, p. 429 (1889). 
