590 ACTION OF POINTS. 



tricity of the opposite kind which had been attracted to 

 the point has escaped at the point and passed to the 

 glass rod, of which it partially neutralised the original 

 charge, being of the opposite kind. The whole charge 

 of the glass rod is, however, not neutralised under these 

 circumstances, because the quantity of electricity which 

 escapes at the point is, at the distance at which the 

 glass rod is held from it, much smaller than the quantity 

 in the glass rod; but if the latter is brought into the 

 close vicinity of the point, its charge may be completely 

 neutralised. If the spherical conductor is strongly 

 charged, and the point of a needle which is held be- 

 tween the fingers is brought to within about l mm of it, 

 scarcely the faintest spark will be obtained when the 

 conductor is afterwards touched with the finger ; on the 

 other hand, if no point be previously brought near and 

 thus allowed to neutralise the charge of the con- 

 ductor, a smart spark will be obtained from the con- 

 ductor if the finger is brought into contact with it. 



The point attached to the neutral body becomes 

 electrical by the inductive action of the electrified body 

 near it. Its electricity is of the opposite kind and the 

 dispersive action of the point causes it to be rapidly 

 transmitted to the electrified body, where it partially 

 neutralises the original charge. If the neutral body 

 is insulated, electricity of the same kind as that of the 

 electrified body near it will thus gradually accumulate 

 in it, and the ultimate effect will be that the point in 

 this case appears to collect electricity, while, as we have 

 seen, a point attached to an electrified body tends to 

 disperse the electricity. Nevertheless both effects are 

 due to the same cause, viz. to the dispersive action oi 



