70 ELEMENTS OF STATIC ELECTRICITY. 



that point ; since the removal of electricity from any 

 point on a surface creates a difference of potential be- 

 tween that and surrounding points, producing an elec- 

 tric movement in the direction of the point of no 

 .resistance, which must extend to every part of the sur- 

 face, and continue till equilibrium is restored. 



Instead of the cylinder with cone-shaped ends, we 

 may use one with needles attached to the ends, as repre- 

 sented in Fig. 15. A wooden cylinder covered with 

 tin-foil can easily be changed in this way. 



It will be impossible to 

 charge such a cylinder, even if 

 only a single needle be at- 

 tached to any part of the sur- 

 face. A projecting angle on 

 any part of a conductor will 

 tend to produce the same re- 

 sult. 



Effects somewhat analogous 

 to these may be obtained by 

 W i7h Points Dipping into water a spherical 

 Attached. body, and also a sharp-pointed 



spike having the same amount of surface. On lifting 

 out the spherical body, water will adhere to it, and col- 

 lect in a large drop at the lowest part ; being held there 

 by adhesion and atmospheric pressure. But if the 

 spike be lifted out, point downwards, the water will 

 drop off when it reaches the lowest point, there being 

 no surface there on which it can be retained by those 

 forces. 



ELECTRIFIED SPHEROID. If a metal sphere be flat- 

 tened at the poles till it assumes the form of an oblate 

 spheroid, as shown at A, Fig. 16, the face of a cross- 



