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PROFESSOR C. H. LEES: THERMAL AND ELECTRICAL; 
and the results obtained. The first section deals with measurements of the thermal, 
the second with measurements of the electrical, conductivities of certain metals and 
alloys, and the third section compares the results with the electronic theories. 
Section I. —The Thermal Conductivity Measurements. 
Outline of Method Used. 
When the thermal conductivity of a substance which conducts heat readily has to 
be determined, it is advisable to give the material the form of a wire or thin rod and 
to allow the heat to flow along the axis. By this arrangement it is easy to insure 
that the difference of temperature to be measured is not too small, and it Iras been a 
favourite one with observers. Sometimes the rod has been exposed to the air of the 
room, as in the original experiments of Biot,* sometimes enclosed in a vessel as in 
those of Wiedemann and Franz, t As the present experiments were to be carried 
out at temperatures down to that of liquid air, the former method could not be used 
without entailing an excessive loss of heat from the sides of the rods. The method of 
enclosure was therefore adopted. 
The scale of the apparatus was mainly determined by the necessity of lowering its 
temperature to that of liquid air and maintaining it at that temperature. This leads 
to a reduction in the size of the rods, and must be compensated by an increase in 
the accuracy of the heat and temperature measurements. This was secured by 
communicating the heat to one end of the rod and measuring it electrically, and by 
determining the difference of temperature at two points of the rod by means of two 
platinum thermometers. 
The Apparatus. 
The metal rods used, Pt, fig. 1, were circular cylinders 7 to 8 centims. long, 
'585 centim. in diameter, and were accurately turned out of larger rods. In use 
they were placed vertically, the lower end fitting into a copper disc, D, of 2'69 centims. 
diameter, 1‘2 centims. thick in the centre, 1 centim. thick at the circumference, which 
in its turn fitted accurately into the lower end of a copper cylinder, T, of 2'69 centims. 
internal, 3’32 centims. external, diameter, 9'5 centims. long, closed at the top. 
On the rod three thin brass sleeves,j A, B, and C, 0'66 centim. long, were placed, 
the fit being of such a nature that the sleeves could be slid along the rod with the 
fingers without the application of more than a small force. § 
* J. B. Biot, ‘Traite de physique’ (1816). 
t G. Wiedemann and R. Franz, ‘Ann. der Phys.,’ 89, p. 497 (1853). 
\ I had not succeeded at this date in making thin mica rings which would stand the wear of use with 
the whole of the rods, see p. 428. 
§ For the accurate turning and fitting of the rods and sleeves I am indebted to Mr. E. T. Cook, the 
Mechanician of the University of Manchester. 
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