of Edinburgh, Session 1883-84. 
293 
Monday, Vlth December 1883. 
EGBERT GRAY, Esq., Vice-President, in the Chair. 
The^following Communications were read : — 
1. On the Change in the Peltier Effect due to Variation of 
Temperature. By Albert Campbell. Communicated by 
Professor Tait. 
The object of this short paper is to give the results of some 
further experiments made with a view to determine the variation 
in the Peltier Effect due to change of temperature. These experi- 
ments are the continuation of a set of similar experiments described 
in a paper read to the Society in summer 1882. 
The arrangement used was almost exactly the same as that 
employed in the former experiments — the measurements being 
made by means of an iron-German-silver thermopile bent into the 
shape of an arch, with the ends about \ inch apart, and placed so 
as to almost touch the junctions of the metals whose Peltier Effect 
was to be measured. 
The neutral-points of the various pairs of metals were also 
measured in the usual way by heating up a junction in oil, plotting 
the temperature-deflection curve, and from it deducing the neutral- 
point. According to theory, the ratio of the Peltier Effect at 
temperature to that at ifg, is determined solely by the values of 
q, and the neutral-point of the metals used; therefore it was not 
necessary to draw the thermo-electric lines of the metals. 
As I have no satisfactory measurement of the neutral-point of 
Pb-Arg, in this case the calculated ratio in column V. is from 
Professor Tait’s diagram. 
In the subjoined table, column I. gives the name of the pair of 
metals ; II. and III. the lower and upper temperatures at which 
the Peltier Effect was observed ; IV. the ratio of the Peltier Effects 
at these two temperatures from the direct measurement ; V. the 
ratio calculated from the observed neutral-point given in VI. 
VOL. XII. 
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