1888 - 89 .] Mr A. Campbell on Thermoelectric Properties. 85 
many hours) the temperature of these cold junctions rose gradually 
from 7 ° ‘2 C. to 8°‘l C. The readings were all reduced to 7 ° ‘2 C. by 
a suitable correction. 
For each reading the temperature of the hot junction was allowed 
to rise till almost perfectly steady, and then four deflections taken 
alternately to opposite sides of the scale. The mean of the four was 
taken as the reading. To keep the deflections well on the scale the 
sensitiveness of the galvanometer was altered when the deflections 
became large. Thus three sets of readings [(A), (B), and (C) in the 
Table] were obtained. These were pieced together by making one 
point in set (B) lie on the curve got from set (A), and then reducing 
all the other numbers in set (B) in the same proportion. Then 
set (C) was pieced on to (B) in a similar manner. The points 
marked * in the table were those by which the joining was effected. 
Of course, they are omitted in the diagram. 
The table gives in the second column the temperature of the hot 
junction, and in the third column the observed deflections reduced 
to cold-junction-temperature 7° *2 C. It was found that up to at 
least 68° *5 the deflections (D) agreed very nearly with the formula 
D = 33*62(£ - 7*2) , 
t being the temperature of the hot junction; so that the curve is a 
straight line. From 74° *4 C. up to 150° C. the readings agree very 
fairly with the formula 
D= - T348/2 + 79-22* -2879, 
i.e ., a parabola whose vertex is at 
t= 293°*8. 
The last two columns in the table give the values of D calculated 
from the two formulae above. The curve in the diagram is from the 
second and third columns. At 8° C. the position of the line of this 
allpy in the thermoelectric diagram is between the iron and copper 
lines. 
In conclusion, we see from the above formulae that from 7° C. up 
to about 73° C. (the melting point), the line of this specimen of 
Wood’s metal runs very nearly parallel to the iron line, and that at 
the melting point it takes a sudden bend away from the iron line, 
but almost immediately bends towards it again, keeping straight till 
