5G9 ] 
X. The Absolute Th ermal Conductivities of Iron and Cojoper. 
By R. Wallace Stewart, B.Sc. [Lond.), Assistant Lecturer and Demonstrator in 
Physics, University College, Bangor. 
Communicated by Lord Kelvin, Pres. P.S. 
Received March 2,—Read March 23, 1893. 
The experiments described in this paper were undertaken at the suggestion of Pro¬ 
fessor A. Gray, M.A., University College, Bangor, with the object of contributing 
something to the results still pecessary to establish the experimental work bearing 
on the absolute thermal conductivity of metals on a more satisfactory basis. They 
were also intended to furnish a determination of the absolute conductivity of pure 
copper at different temperatures. 
The data already accumulated'" on the thermal conductivities of iron and copper 
are due chiefly to Angstrom, Forbes, Neumann, Tatt and Mitchell, and more 
recently to Kirchhoff and Hansemann and Lorenz. 
Forbes first published, t in 1861 and 1865, the details of his determination of the 
conductivity of iron, and showed that its value diminished with rise of temperature. 
Some years later Tait confirmed^ this result, and in addition gave determinations of 
the conductivities of copper, lead, &c. His results for copper showed that, unlike 
iron, its conductivity increased wdth increase of temperature. Angstrom, however, 
in 1861, published^ results for iron and copper, evidently obtained with great care and 
by a very reliable method, which showed that the thermal conductivities of both 
metals decreased with increase of temperature. As pointed out by Tait, both 
Angstrom and Forbes omitted to correct their results for change of specific heat witli 
temperature, but the application of this correction does not materially affect the 
nature of their results. NeumannH also determined the absolute conductivities of 
* See table giA^en below, p. 688. 
t ‘Trans. Roy. Soc. Edinb.,’ vol. 23, pp. 13.3-146, and vol. 24, pp. 73-110. A preliminary comninni- 
cation bad previously been made to tlie British Association at Belfast in 1852. 
+ ‘ Trans. Roy. Soc. Edinb.,’ 1878. 
§ Communicated to the Royal Swedish Academy in January, 1861. German and English translations 
of his paper are to be found in Poggendorfp’s ‘Annalen’ for 1863 and in the ‘Phil. Mag.,’ 1863 (first 
half-year). 
II ‘Ann. de Chim.,’ vol. 66, pp. 183-185. 
MDCCCXCIII.—A. 4 D 
28.8.93 
