THE THERMAL CONDUCTIVITY OF METALS. 185 


Pratixum Wire (not annealed). Diameter = °202 centim. 
: see : 
Thermal conductivity. | Electrical resistance. 
| hl 
1861 | 9180 | 

Here the thermal and electrical conductivities are each 19 per cent. of the 
conductivity of copper. 
The gold, platinum, and silver were afterwards carefully annealed by Messrs. 
JoHNson, Matruey, and Co., and the conductivities again determined. In each of 
the cases the alteration due to annealing was less than 1 per cent. both in electrical 
and thermal conductivity. 
The results for the different metals are therefore— 
MEAN Conductivity between Temperatures 10° C. and 97° C. 

{ 
| Diameter. 
millims. 
Copper—Specimen 1 =| 9594 | 2:00 
Hf Dh name eee | “8884. 211 
RU erie ere | 8612 | 3-09 
| Very Ms ACS al as) eere| 3497 | 2°04 
impure _ OR Oe ey leet meee eh | 3198 2-04: 
DL Ver aera Mine | Spc les one cts 9628 | 2:02 
Gold) (x qs ce ape ee eo | “7464. 2:00 
IBlatingims ot «fo Serio ieee) ee Sl 1861 | 2:00 




It is intended to use other liquids than boiling water to heat one end of the wire, and 
in this way test the alteration of conductivity with temperature. Up to the present 
time no alloys have been tested, but it is intended that tests should be made of some, 
such as platinoid and German silver ; also iron, as pure as possible, might be tested. 
Instead of boiling water, steam was used for some time in this investigation, and 
was in some respects found to be more convenient. Fig. 7 is a sketch showing a 
section through the middle of the apparatus. 
The steam is generated in the vessel W, passes along the upper tube T in the 
direction of the arrows, and blows directly on the end of the wire, afterwards passing 
out through the outside copper tube P, and escaping by the outlet B. 
The thermometer D indicates the temperature of the steam just when it strikes the 
wire. It will be seen that the outer tube with the steam in it serves as a steam 
jacket, and thus keeps the steam in the inner tube T at a high temperature. The 
sloping bottom where the wire is fixed at A isso made to prevent water accumulating 
there. To ensure that as much steam as will supply all the heat that the copper can 
take up is impinging a A, it is only necessary to arrange that the steam emerges at 
B as steam. 
MDCCCXCV,—A. : 2B 
