PHILOSOPHICAL TEANSACTIONS. 
I. On the Influence of Temperature on the Electric Conducting Power of Metals. 
By Augustus Matthiessen, F.B.S., and Moeitz von Bose. 
Received December 5, 1861, — Read January 16, 1862. 
The results obtained by different observers in their researches on the influence of 
temperature on the electric conductiug power of metals do not agree at all together. 
The differences in their results may be partly owing to their not having tested pure 
metals, and partly to their not having taken into consideration the fact that, when a 
wire of a pure metal is heated for the first time to 100° C., an alteration in the con- 
ducting power of the \vire is observed on its again being cooled ; in fact, it is necessary 
to keep the wire for several days at 100° before its conducting power, on again being 
cooled, becomes constant. 
In the experiments we are about to detail we have taken great care to employ only 
pure metals, as well as a method and a disposition of the apparatus with which great 
accuracy could be obtained. 
The method employed for the determination of the resistances is fully described in 
the ‘Philosophical Magazine’ for February 1857. Fig. 1 shows the disposition of the 
apparatus. B is the trough in which the wires were heated: these were soldered to 
two thick copper wires F (4-5 millims. thick), bent as shown in the figure, and end- 
ing in the mercury-cups E, which were connected with the apparatus by two other 
copper wires, F', of the same thickness. C is a piece of board placed in such a manner 
as to prevent the heat of the trough from radiating on the apparatus. The mercury- 
cups O are made of small blocks of wood, through which holes are bored just large 
enough to take the thick wires, and to the bottoms of which blocks amalgamated copper 
plates are fastened. Now it is clear that if the ends of the thick copper wires are filed 
flat, and well amalgamated, and the mercury-cups are filled with mercury, this method 
of connexion may be looked upon as a soldering of the copper plates to the wires, or, 
in other words, as a perfect connexion ; for the wires may be removed as often as 
required, and on replacing them the same resistance is always observed. The wires F", 
MDCCCLXII. B 
