CAPACITY OF GLASS, AND OF LIQUIDS. 
367 
two of a set of four horizontal rods of varnished glass. The plates can thus be placed 
parallel to each other at any distance apart that may be desired. The distance 
between the pldtes was measured by a pair of common callipers and a millimeter rule to 
the nearest \ nlillimeter, For convenience, let the plates be named A, B, C, D, E, as 
Fig. 5. 
Half full size. 
in the accompanying diagram. In a first experiment B and D were respectively con¬ 
nected to the quadrants of an electrometer of which the jar was charged in the usual 
way. A and E were connected to one pole of a battery of 20 AgCl elements, C to 
the other pole through an ordinary electrometer reversing hey, E was adjusted till 
the disturbance of the image was a minimum, when the key was reversed. This 
method was unsatisfactory, probably because in the act of reversing all the plates 
A, C, E were momentarily connected to one of the poles, and also because the insula¬ 
tion of the plates B, D was imperfect. The experiments, however, sufficed to prove 
beyond doubt that the instrument gave diminishing values to the specific inductive 
capacity of glass, as the distance of the five plates from each other was increased from 
12 millims. to 32 millims., also that it gave values less than unity for the specific 
inductive capacity of brass in the form of a plate 3 '5 millims. thick. More satisfactory 
