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VII. Polarization of Metallic Surfaces in Aqueous Solutions. On a new Method of 
obtaining Electricity from Mechanical Force , and certain relations between Electro- 
static Induction and the Decomposition of Water. By Cromwell Fleetwood 
Varlet. Communicated by Sir W. Thomson, F.B.S. 
Received October 5, 1870, — Read January 12, 1871. 
In 1860, having need of condensers of enormous capacity, the author found that pla- 
tinum plates immersed in a solution of sulphuric acid and water had enormous capacity, 
and could, under certain conditions, be used as condensers with potentials below that 
necessary for decomposing water. 
When one of the platinum plates was replaced by mercury, and a powerful battery 
was applied so as to make the mercury negative, the latter flattened out and increased 
its surface. 
When a pasty amalgam was employed of the proper consistency on a flat surface, this 
flattening out was sometimes increased to more than double the original surface. The 
reversion of the current immediately brought the amalgam to its original dimensions. 
This experiment suggested a means of obtaining dynamic electricity by reversing this 
process. 
Plate II. fig. 1 represents a large glass vessel (A) cemented into a groove in the board B. 
The funnel-shaped glasses C and D, which are inside A, are connected with E and F 
outside of A. Under the board B is fixed a transverse bar of wood, so that the whole 
can be rocked from side to side. When tilted to the right the mercury in C runs into 
E, while that in F runs into D. The reverse operation takes place when the hoard is 
tilted to the left ; consequently when the surface of mercury in C is diminished, that in 
D is augmented, and vice versa. The galvanometer G connects the two by the spiral 
wires W. 
The glass vessel (A) is filled half full with diluted sulphuric acid. If the two poles 
of a voltaic battery be immersed in A, the positive pole in connexion with the acid and 
water, the negative in connexion with the mercury in C, the latter becomes polarized 
with “ nascent hydrogen.” 
The mercurial surface in C will retain its polarity for a long time after the removal 
of the polarizing-battery. 
If the two cups E F be now connected by the galvanometer G, a current of electricity 
will be seen to flow between them, the polarization will be equally shared by the two 
mercurial surfaces, and then the current will cease. If, now, the board be rocked from 
right to left, and vice versa, the mercury surface in the one vessel will diminish, while 
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