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Mr Wilson, A curvature method, etc. 
A curvature method for measuring surface tension. By C. T. R. 
Wilson, M.A., F.R.S., Sidney Sussex College. 
\Read 28 January 1907.] 
To measure the surface tension of mercury a circular hole 
of about a mm. in diameter is made through a glass plate closing 
the upper end of a vertical tube. The tube is filled with mercury, 
and sufficient pressure is applied to give a suitable curvature to 
the meniscus projecting into the aperture. 
The curvature is measured by making the meniscus serve as a 
convex mirror. A microscope is focussed (1) on the centre of 
curvature (when a reflected image of the eye-piece cross- wires will 
be seen in focus), (2) on a fibre stretched just above the meniscus, 
(3) on the virtual image of the fibre formed by the meniscus. 
From the vertical displacements of the microscope between these 
three positions the radius of curvature is obtained. If the pressure 
be changed by a known amount between two such measurements 
of curvature we can deduce the surface tension, for we have 
