of Edinlurgh, Session 179 
rausch ; and this method is no doubt the most general and most 
accurate which has yet been applied. 
It occurred to me some years ago that electrometer measurements 
might give results sufficiently accurate for most practical purposes. 
To measure the difference of potential between the electrodes by 
which the current enters and leaves the electrolyte is of course out 
of the question ; but by dipping into the liquid two otherwise insu- 
lated platinum points which are connected to the electrometer, we 
may minimise the effect of polarisatiou. 
The apparatus used in the experiments to be described was con- 
structed fully a year ago, and was simply a horizontal glass tube (1 1‘8 
cm. long) fused into the sides of two vertical test-tubes, and having 
two platinum wires fused into it at points distant 7 '3 cm. from 
each other. The platinum points just projected into the inside of 
the tube, the bore of which was 0‘9 sq. cm. in cross-section. The 
electrolyte stood in the vertical tubes at a sufficient height to fill 
the horizontal connecting tube completely; and into the vertical 
tubes platinum plates were inserted to act as the current electrodes. 
A current from two Bunsen cells was driven through the electrolyte 
