CAPACITY OF GLASS, AND OF LIQUIDS. 361 
4°. e, f, g, It, k connected together. 
5°. Connection of k and h broken. 
In other words we ha ve¬ 
il 0 . Initially r Guard ring. 
< Guard ring condenser plate, and 
L One pole of battery. 
f Sliding condenser. 
1 Other pole of battery. 
2°. All condensers insulated. 
3°. f Guard ring. 
L Earth. 
f Guard ring condenser plate. 
I Sliding condenser. 
4°. Mixed charges to electrometer. 
5°. Electrometer insulated. 
Mixing of charges. 
The whole switch, binding screws and all, is covered with a brass cover connected to 
earth and provided with apertures for the connecting wires. The ebonite legs which 
carry the pieces a, b, c, cl, e f, g, k are attached to a brass base plate, so that if any 
leakage occur from a, b, c, cl, e, or f it shall be to earth and not to the electrometer. 
The connecting wires are insulated with gutta-percha, covered with a metallic tape as 
an induction shield, this tape being of course connected to earth. 
The mode of experiment was substantially as before. A glass plate was introduced 
in the guard ring condenser, and the sliding condenser adjusted till the capacities 
were equal; the glass plate was removed and the guard ring condenser, with air as its 
only dielectric, was adjusted till its capacity was equal to that of the sliding condenser. 
In every case the battery was reversed and the mean taken. 
The following tables give the results obtained:— 
All measures are given in terms of turns of the micrometer screw of the guard ring 
condenser, of which there are 25 to the inch. 
Column I. gives the circumstances of the particular experiment. 
Column II. the distance between the plates of the condenser with glass in. 
Column III. the same distance with air only when the capacity is the same as in II. 
Column IV. the thickness of air plate equivalent to glass plate. 
Column Y. resulting value of K. 
