On Electromotive Force and Surface Tension. 89 
the electro-motive of a single Leclanché cell is employed. By 
using « micrometer screw the distance across which polarization 
can occur so as to produce contact can be estimated, and thus a 
- ready means of measuring the E.M.F. of a cell suggests itself, after 
the manner of Lippman’s delicate capillary electrometer. It is 
not impossible that a useful practical application of the simple 
arrangement might be made in connexion with telegraphy. 
The liquid I have used in contact with the mercury is glycerine 
and water, as it is not sufficiently conducting to allow of more 
than very slight electrolytic action taking place. 
