360 
DR, J. HOPKINSON OH THE ELECTROSTATIC 
Pig. 4. 
Section on line s, t, w. 
determine capacities when the residual charge was great, as in the case of plate glass, 
and was unsatisfactory to anyone who held that flint glass condensers discharged very 
much more in a time comparable with one second than in a minute fraction of a second. 
The new switch was arranged to effect the further operation of breaking contact 
between the condensers and the quadrant immediately after the contact was made. 
It is also arranged for much higher insulation, the old switch being quite useless for 
the greater battery power used. 
a, c are stiff insulated horizontal contact bars connected to the two poles of the 
battery, d, e, f are insulated springs normally touching a and c on the under side, 
d is connected by a wire to the guard ring, e to the plate of guard ring condenser, 
f to the sliding condenser, b is an insulated binding screw connected wuth c for the 
purpose of more conveniently introducing the battery wire. 1 is a spring connected to 
earth, k is a stiff insulated piece, carrying an adjustable point m, normally in contact 
with the upper side of the insulated spring A. From k a wire leads to the quadrant of 
the electrometer, k can at any moment be put to earth by a spring key. The 
insulated spring g has its end between e, f, and A, and is normally in contact with 
neither. The springs d, e, f can be simultaneously bent downwards by an insulated 
plunger. When this plunger is struck downwards we have the following operations 
effected in a fraction of a second— 
1°. Cd and e are in contact with a. 
L f in contact with c. 
2°. d, e, and f insulated. 
3°. rd connected to l. 
\ e, f, and g connected together. 
