VIII 



THERMO-ELECTRIC CRYOSCOPY 



161 



one would like to connect the leads coming from 

 the junctions on the pine supports directly with 

 the terminals of the galvanometer. The importance 

 of reversing the current through the galvanometer owing 

 to shifts in the zero position of the mirror, and the 

 advantages of being able to disconnect the couple readily 

 from the galvanometer during various manipulations, 

 render a key of some form or other necessary in the circuit. 



50 



100 150 



Deflection in millimetres 



Fk!. 26. 



200 



250 



Such a break in the continuity of the leads involves a 

 pair of junctions. Experience shows that even when the 

 junctions are between two pieces of the same wire, thermo- 

 electric effects are produced if they are not at the same 

 temperature. In order to keep the two junctions as closely 

 as possible at the same temperature, the following arrange- 

 ment was adopted : 



The leads coming from the couple are disposed so that 



M 



