of Edinburgh, Session 1877-78. 615 
be inserted between the electrodes of a decomposing cell it ought, 
except in extreme cases, to produce almost precisely the same 
result as a similar and equal slip of glass or mica. This was easily 
verified. Here we have the singular result of a marked diminu- 
tion of the current by the insertion into the electrolyte of a sub- 
stance which is in itself a much superior conductor. Even when 
the platinum completely closes the path from one electrode to the 
other, so as to form two decomposing cells instead of one, a compara- 
tively small hole made in it at once changes its function from 
that of common electrode to each of two decomposing cells into that 
of a mere obstruction in one cell. It is an interesting experimental 
inquiry to trace the intermediate stages between these two states, as 
a pinhole in the platinum is gradually enlarged. Whatever, then, 
be the behaviour of the particles of an electrolyte, they do 7iot 
behave like little pieces of platinum. 
5. Note on Thermal Conduction. By Professor Tait. 
Monday , 6th May 1878. 
Sir C. WYVILLE THOMSON, Vice-President, in the Chair. 
The following Communications were read : — 
1. On the Indications of Molecular Action in the Telephone. 
By II. M. Ferguson, Ph.D. 
The accepted theory of the telephone represents that the vibra- 
tions of the sending plate to and from the pole of the magnet before 
which it is fixed is the origin of the currents generated in the pole 
bobbin of wire, and that these currents transmitted to the receiving 
telephone produce corresponding to-and-fro excursions of its plate. 
This theory, which is that of the inventor, may be shortly desig- 
nated, in the happy words of Sir William Thomson for a kindred 
action, the push-and-pull theory. We have had in this session of 
the Society two communications of a practical nature, which seem 
directly confirmatory of this view. I refer to the lucid exposi- 
tion of Gott’s telephone experiment in the island of St Pierre, and 
