of Edinburgh , Session 1876-77. 
423 
line lay very far down on the thermo-electric diagram, while subse- 
quent observations showed that it lay below all the lines formerly 
obtained. Hence it lies in a region in which it is very difficult 
accurately to determine its position. This difficulty is increased 
by the circumstance that the line which lies nearest it, namely, 
that of nickel, is not a straight line. Another difficulty in carry- 
ing out the experiments arose from the shortness of the cobalt bars, 
but this was in a great measure overcome by the use of a slight 
modification of the apparatus devised for the determination of the 
thermo-electric properties of sodium and potassium, formerly de- 
s 
scribed to this Society.* The following is a brief account of the 
experiments and their results : — 
In the beginning of March one of the bars was ready for use. 
Preliminary observations carried on with hot oil having shown that 
no marked peculiarities existed within the temperature of boiling 
oil, a quadruple junction of M, N,f nickel and cobalt was formed 
and heated by means of a red-hot iron cylinder. The nickel- 
cobalt deflections obtained from this experiment, when plotted in 
terms of the M-N deflections, gave a line showing clearly the nickel 
peculiarities, and supplied us with an approximate position for 
cobalt. 
On the opening of the laboratory for the summer session experi- 
ments with the hot cylinder were resumed, and a quadruple junction 
of M, N, palladium, cobalt, was used. This was connected with 
the galvanometer in such a way that the deflections due to the 
thermo-electric pairs Pd-Co, M-N, M-Pd, could be read separately, 
and in rapid succession. The M-N junction supplied us with a 
temperature scale as in former experiments, and the lines got by 
plotting the other deflections in terms of this gave an easy method 
of fixing the relative positions of cobalt, palladium and M, and hence 
of fixing the position of cobalt on the thermo-electric diagram.” 
Owing to the much greater electro-motive force in the Pd-Co and 
M-Pd circuits than in the M-N circuit, a resistance of 192 ohms 
had to be inserted between the palladium wire and the galvano- 
meter. The M-Pd curve presented the usual well-known parabolic 
* Proc. Key. Soc. Edin. 1873-4, p. 350. 
t Trans. R. S. E. 1872-73, p. 138. 
