ON THE ELECTRICAL PROPERTIES OR PURE SULPHUR, 
147 
The partly insoluble plates were annealed in some cases in order that the difference 
of specific inductive capacity might be observed in one and the same plate. The 
annealing produced both buckling and cracking ; the latter does not matter, and the 
former has been dealt with. In cases where the plates were annealed the analysis 
was made on samples collected during the turning or milling of the final surfaces. 
The formula of calculation is best given in the following form :— 
- — ( Pi + Pi \ 8 
- I\ U/K + pj ’ 
where F and Fj are the forces observed, (p : + p 2 ) is the distance between the fixed 
and suspended plates, p 1 is the thickness of the sulphur, and K is the quantity we 
are in search of. The results will be sufficiently evident from the following table, 
which includes unsatisfactory values as well as satisfactory ones. The former are 
included with a view of showing how we gradually improved our results as we 
eliminated various sources of error—-bad conductivity of silver coating, irregularity of 
driving, effect of brushes due to imperfect dusting, or too high voltage, &c., &c. 
