258 
Proceedings of the Royal Society of Edinburgh. [Sess. 
adjustment. Owing to the sparking at d it was found necessary to arm 
the terminals with pieces of platinum. These pieces were riveted on, not 
soldered. They are 2-3 mm. thick, and their flat polished surfaces are 
about 2 mm. square. 
By means of the cell shown in fig. 4, polarisation and the heating effect 
of the current are avoided. 
The following points were found to be important : — (1) The cross-section 
of the liquid between the electrodes must not be too small, or heating cannot 
