CAPACITY OP GLASS, AND OF LIQUIDS. 
357 
determined by the following method, which I arranged for myself, unaware that a 
similar method had been used by Mr. Sabine.* A condenser of known capacity is 
connected to A through a known resistance ; the condenser receives a known charge 
whilst connected to the electrometer ; the piece B is struck by the pendulum, and the 
Fig. 1. 
remaining charge is observed. Two experiments were made ; in each the condenser 
was of tinfoil and paraffin, such as are used by Messrs. Clark, Muirhead, and Co. 
for telegraph purposes, and had a capacity of 0'29 microfarad. The resistances were 
respectively 512 ohms and 256 ohms. The results gave respectively duration of 
discharge 0 0000592 second and 0‘0000595 second. We may take it that the dura¬ 
tion of discharge was less than 0‘00006 second. The condenser was now replaced by 
the flask. The flask was charged for some seconds from the battery, was insulated 
and discharged by the pendulum, and the remaining charge read off on the electrometer 
so soon as the image came to rest. In a first experiment the charge was from four 
elements ( = 444 divisions of the scale), and the charge remaining gave deflection 
34 divisions. In a second experiment the charge was from eight elements ( = 888 
divisions), and the remaining charge was 61 divisions. Even this small residual 
charge is largely due to the inductive action of the needle of the electrometer on the 
quadrant connected to the flask. To prove this, the experiment was varied by begin¬ 
ning with the quadrant separated from the flask, and only connecting these after 
discharge had been made. With eight battery elements, the remaining charge in the 
flask was found to be 25 divisions; with 20 elements, 61 divisions. From these 
experiments we may conclude that, if a flask of light flint glass be charged for some 
seconds and be discharged for 0‘00006 second, the residual charge coming out in the 
next three or four seconds is certainly less than 3 per cent, of the original charge. It 
* Philosophical Magazine, May, 1876. 
3 A 2 
