1558 
DR. J. HOPKINS ON ON THE ELECTROSTATIC 
was important to learn if this 3 per cent, was sensibly diminished if the time of 
discharge was somewhat increased. For this purpose the time of oscillation was 
increased, and the arrangement of piece B and knife-edge C was duplicated, so that 
the flask was twice discharged within an interval of about second between. The 
result was, with charge from eight elements and the flask initially connected to the 
Fig. 2. 
quadrant, a remaining charge of G 'l divisions, exactly the same as wdien the discharge 
only lasted 17 1 00 second. I conclude that, with this glass, it matters not whether the 
discharge of the flask last tto ow second or g 3 ^ second ; its capacity is the same. 
This is in precise accord with what Sir W. Thomson told me before I began the 
experiments for my former paper. 
(II.) Determinations with the guard ring condenser * 
It has been suggested that my former results were liable to uncertainty from the 
small potentials used and from the comparatively long time of discharge. The main 
purpose of the present experiments has been to ascertain the force of the objections. 
As the principle of the method is the same as in the earlier paper, it is only needful to 
explain the alterations the apparatus have undergone. 
The battery .—A chloride of silver battery of 1000 elements was constructed and 
very carefully insulated, both as regards cell from cell and tray from tray. Each tray 
contained 50 cells and the set of 20 trays was conveniently enclosed in a wooden case 
provided with suitable terminals. As my experience of the battery is but short 
* The cost of the additional instruments used has been defrayed by a Royal Society Grant. The 
battery and some of the other instruments were made by Messrs. L. Clark, Muirhead, and Co., the 
remainder by Mr. Groves. 
