ELECTRICITV. 513 



6. Influence of balls and points. 



It has before been stated under (he head Distribution of 

 Electricity, that the fluid accumulates itself in a state of 

 great intensity at the pointed extremities of a charged 

 body, where it passes off in continued streams. On this 

 account a body containing any sharp or pointed parts, 

 can with great difficulty be charged with electricity. 



On the other hand if a body with all its extremities 

 properly rounded, is charged and brought, when in that 

 state, into the vicinity of any pointed bodies, its electrici- 

 ty is immediately and rapidly drawn off. So marked and 

 powerful is this effect that the greatest care is necessary, 

 or the successful operation of the machine will be entire- 

 ly prevented by the accidental presence of pointed sub- 

 stances in the vicinity. To avoid this every part of the 

 machine and of the apparatus about it, should be round- 

 ed, every wire should be terminated by a ball, no 

 roughness or raggedness of any kind should be left, 

 all dust should be removed, and every sharp or pointed 

 body should be taken away from the vicinity. A sharp 

 needle, held at the distance of several feet from the prime 

 conductor, will often effectually prevent its being charg- 

 ed. There are various distinct experiments by which 

 this influence of points may be strikingly shown. 



1. Attempt to charge the prime conductor and while 

 doing so hold at a little distance from it a needle with 

 the point towards it. The effort to charge the conduc- 

 tor will be vain, the electricity will pass off to the point 

 as fast as it enters the conductor, and in the dark, a lu- 

 minous star will be seen Upon the point of the needle. 



2. After the jar is charged bring a brass ball to it, and 

 observe the size of the spark. Then charge it again and 

 attempt to obtain a similar spark by means of a poinltd 

 body. The result will be that the electricity will pass to 

 the point silently, before it comes near enough for the 

 spark. 



3. The discharger, heretofore described, is usually 

 made with balls at the extremities, so constructed that 

 they may be unscrewed, leaving the extremities of the 

 wire pointed. If now the jar be charged, and then dis- 



VOL. i. NO. xxi. 45* 



