THE THERMAL CONDUCTIVITY OF METALS. 183 
more expensive metals had not been determined, although relative values had been 
found by WIEDEMANN and FRANz.* 
I am very much indebted to Messrs. Jonnson, Marrury, and Co. for their great 
kindness in preparing and lending to me wires of gold, platinum, silver, and other 
pure metals, of 2 millims. diameter, and of such a length as to enable me to measure 
without difficulty. both the thermal and electrical conductivities. 
Unfortunately, I cannot find a record of the value obtained for the electrical 
conductivity of the gold wire, and it has been returned some time ago. As, however, 
Messrs. Jonnson, Marruey, and Co. stated, when sending it, that it was as pure as 
could be made, it will perhaps be sufficient for me to use the value that has already 
been found for the electrical conductivity of gold as determined by other experi- 
menters. : 
The curves for the calculation of the conductivity of silver wire are shown in 
Diagram II. The values for the different lengths are given below. 
SILVER Wire. 

Thermal conductivity im 
Length. C.G.S. units between 
15° C. and 98° C. 


7°86 956 
6°59 960 
6°59 963 
a6] 973 


It will be observed that the second and third values, although for the same length, 
differ by about 4} per cent. They are both given however, as they agree within the 
limits of observational errors. The mean of these values is °9628. 
As the curves for gold and platinum are very similar to those for copper and silver, 
it may be enough to give the values obtained for their conductivities. 
Gop Wire (not annealed), Diameter = ‘202 centim. 

| . . 
Hlectrical resistance as 
determined by 
Dr. MarruiessEen. 
| 
Thermal conductivity in | 
C.G.S. unit. 

7464 | 2188 
| 
1 



Comparing these values with those for Messrs. GLovER’s copper, which was found 
to be 959, we find that the thermal conductivity of gold is 78 per cent. and the 
electrical conductivity 81°6 per cent. that of copper. 
* © Annales de Chemie,’ vol. 41, p. 107, 1854. 
