280 DR CARGILL G. KNOTT ON 
EXPERIMENT VI. (March 24). 
(Fig. 3; symbol . ). 
Temperature, Deflection (Cu, | Fe,) 
62° C. —66°6 
57 — 68:2 
52 — 64:5 
48 —61°5 
44 —573 
32 —54 
24 —52 
12 —50 
EXPERIMENT VII. (March 25). 
(Fig. 3; symbol x ). 
Temperature, Deflection (Cu, | Fe,) 
70° C. —69 
55 —65 
43 —62 
30 —52 
23 —47 
12 —47 
The conditions under which these experiments were made were the very same 
as those under which the temperature-variation of the iron was investigated. 
The representative curve is shown in fig. 3, all the points clustering approxi- 
mately round a straight line whose tangent of inclination to the temperature 
axis is—'39, measured in diagram units. Hence it appears that the tempera- 
ture-variation of copper is smaller than that of iron, and that consequently, 
since the iron is the more positive metal, the difference of potential between 
iron and copper falls off as the temperature of both is raised—a result already 
obtained in the earlier experiments (see page 275). 
Zine was the next metal which came under investigation. At first it was 
electrified by contact with aluminium, kept polished at a constant temperature. 
This latter metal, however, is not very suitable, on account of its proneness to 
rapid change in time as evidenced by its curve on the diagram (fig. 1, c). 
Nevertheless the same negative growth of the heated metal was indicated, and 
more self-consistent results were obtained by contact of zinc hot with zinc cold, 
both polished as usual. The numbers are as follows :— 
EXPERIMENT VIII. (March 28). 
(Fig. 4; symbol - ). 
Temperature, Deflection (Zn, | Al,) 
63°°8 C. —78 
46°5 —66 
34 — 64 
21'8 —56°3 
10 —40 
