Transverse Galvanomagnetic and Thermomagnetic Effects. 45 
Signs of the Effects. 
The diagram (fig. 1) indicates the directions of the effects corresponding 
R S Q P 
“f - Warm 
Fig. 1. 
Cold 
Electric 
Current 
Wat 
> 
to positive values of the coefficients ; it being understood that the magnetic 
field is acting downwards perpendicular to plane of paper. 
Apparatus. 
The apparatus and measuring arrangements have been described in 
detail in the author’s earlier paper, and the description need not be repeated 
here. In dealing with the galvanomagnetic temperature effect it was found 
necessary to introduce a modification in order to make the measurement 
possible. This effect consists in a temperature difference set up between 
the two edges of a small plate of metal, carrying an electric current, when 
it is placed in a magnetic field whose direction is perpendicular to the plane 
of the plate. This temperature difference is extremely small, and cannot be 
measured in the usual way by thermocouples attached directly to the plate, 
since with this arrangement the deflections of the galvanometers in circuit 
with the couples are due mainly, not to the temperatures of the junctions, but 
to electromotive forces set up by the current in the plate. Under these cir- 
cumstances it was useless to increase the sensibility of the galvanometers. 
The difficulty was overcome by using, in place of the two couples, a 
small thermopile of ten pairs of junctions. This was built up (see fig. 2) on 
