218 ON MAGNETISM. 



91. Note on thermo-electric or thermo-galvanic 

 currents, and on their possible connexion with terrestrial 

 magnetism. 



In Figure 73, let A and B be two dissimilar metals, 



Fig. 73. 



soldered together at C ; and let their ends D and E be 

 connected by a wire. (The metals found to be most 

 favourable are antimony and bismuth.) Then if heat 

 be applied at their point of union C, galvanic currents 

 will be created through the wire DE, which can be 

 measured by the deflexion of the needle of a galvano- 

 meter. The current which issues from the antimony- 

 end of the combination is of the same quality as that 

 which issues from the graphite-end of a galvanic 

 battery. 



If there be a number of pairs of bars of the same 

 metals, as in Figure 74, and if heat be applied simul- 

 taneously to all the points of junction C, C, C, where 

 the metals follow in the same order, the intensity of 

 the galvanic current through DE is proportionally 



