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II. On the Time-relations of the Excursions of the Capillary Electrometer, ivith a 
Description of the Method of Using it for the Investigation of Electrical Changes 
of Short Duration. 
By George J. Burch, B.A., Oxon. 
Communicated by Professor Bartholomew Prtce, F.R.S. 
Received September 3,—Read November 19, 1891. 
[Plates 3-6.] 
In a preliminary note “ On a Method of Determining the Value of Rapid Variations 
of a Difference of Potential by Means of the Capillary Electrometer,” I indicated 
briefly the results of an investigation of the time-relations of the excursions of the 
capillary electrometer. The object of the present paper is to give further details 
concerning the method of measurement which I then put forward, and to describe the 
experiments which led to it. 
The theory of the instrument has been treated by Lippmann, Hermann, and others, 
mainly from a mathematical stand-point, and the phenomena have been ascribed to 
polarization, but no adequate attempt appears to have been made to establish by 
actual measurement the accuracy of the formula for the time-relations, nor to ascertain 
whether there were any other influences at work besides those assumed in stating the 
problem. Poiseuille’s experiments on the velocity of the flow of liquids through 
capillary tubes seem to have been overlooked, and no sufficient investigation made of 
the effect of the form and dimensions of the tubes upon the rate of movement of the 
meniscus. 
It seemed, therefore, that there was scope for a thorough examination of the 
problem by the experimental method, with a view, not only to the further elucidation 
of the theory, but also to the discovery of the best manner of using the instrument so 
as to render available those special properties which make it unlike any other form of 
electrometer or galvanometer. 
In the course of the investigation, which has occupied more than three years, over 
a hundred electrometers were made, besides many additional capillaries- used in 
preliminary experiments. 
MDOCCXCII.—A. M 
6.4.92. 
