88 Scientific Proceedings, Royal Dublin Society. 
surface tension of the latter will be increased as soon as the 
platinum wire is made the positive electrode of a battery: 
the convexity of the mercury surface will accordingly 
become greater, and thereby it will be brought into contact with 
the closely adjacent electrode. But when this occurs the electric 
polarization of the liquid surface ceases, as the current now passes 
freely through the conducting wetallic circuit of mercury and 
wire; the polarization ceasing the augmented surface tension 
disappears and the mercury falls back to its original flattened 
condition. Contact will thus be broken and electrification again 
occur, the mercury will once more increase in convexity, rise, make 
contact, lose its convexity, fall away, and hence a rapid oscil- 
lation of the mercury ought to occur so long as the electrification 
is continued. A new form of contact-breaker is thus suggested. 
By enclosing the mercury in a capillary tube with another 
liquid over it, and the electrodes arranged as before, a greater 
vertical motion of the mercury should take place, and hence a 
smaller electromotive force ought to produce the rapid interrup- 
tion of the current. This is the principle of the little contact- 
breaker shown in the figure, and which an accidental eircum- 
py 
stance led me first to notice. By enclosing a telephone in the 
circuit the rapid make and break is rendered audible, even when 
