CONDENSERS OF ELECTRICITY. 



611 



should be rubbed over with a little tallow ; a thin covering of tallow 

 prevents the formation of a conducting layer on the surface of the 

 glass very well, and can be simply wiped off' again afterwards. 



47. Condensers of Electricity. Effects of electrical dis- 

 charge. The tendency which electricity has to escape 

 from bodies, its tension, assigns a limit to the quantity of 

 electricity which may be accumulated in a conductor of 



FIG. 322 (an proj. | real size). 



a definite size. A conductor of a given magnitude of 

 surface can only hold a certain quantity of electricity, 

 which becomes less the greater the number of project- 

 ing points, corners, and sharp edges which the surface 

 of the conductor contains. A small disc of thin metal 

 insulated on a stick of sealing-wax, like that at A in 

 fig. 322, gives but very small sparks, whether it is elec- 



B B 2 



