a rapid succession of Electrical Discharges, 329 



can be so insulated as to be perfectly free from this influence ; 

 indeed there can be very little doubt that the air itself induces 

 upon electrified bodies, by assuming the condition of a polarized 

 atmosphere about them. The quantity of electricity which a 

 conductor is capable of taking up, depends upon the extent of 

 its surface and its contiguity to surrounding bodies, these latter 

 by their proximity causing the electricity of the electrified body 

 to become, as it were, latent or disguised ; since if any electrified 

 conductor, placed within a given distance of an uninsulated con- 

 ductoi', exhibit a certain amount of electrical tension, that tension 

 is immediately increased, and its electricity rendered more free, 

 by the removal of the vicinal conductor. 



The quantity of electricity capable of being retained upon the 

 surfaces of the binding screws forming the terminals of the in- 

 duced wire, must be exceedingly small compared with the quan- 

 tity sent forward to them by each induced wave ; and therefore 

 if the wave occupy any amount of time, however small, certain 

 portions of the eiFect transmitted to the terminals will pass for- 

 ward, impelled by those from behind, and the discharge will be 

 stream-like. This being the case, the electricity will pass with 

 a less force through external circuits, uniting the terminals than 

 through the induced wire itself, since these circuits have no 

 magnetism inducing on them to give direction and force to the 

 current, and simply therefore offer resistance which retards the 

 current and diminishes its effect, as is sti'ikingly evident when 

 an external circuit of three or four miles is introduced. It can 

 hardly be expected, then, that greater thermal effects will be pro- 

 duced in the external circuit than in the induced wire itself. If 

 the conducting surfaces of the terminals be increased, they assume 

 the condition of insulated conductors, whose electrical tension or 

 intensity will be gradually less than that of the simple terminal, 

 in proportion as their surfaces increase and they are brought 

 under the influence of external induction. This is evidenced by 

 the greater brilliancy and increased noise of the spark, and by a 

 gradual diminution in its length. If these conducting surfaces 

 be so far increased as to be al)le to contain all the electricity sent 

 forward to the terminals by each wave and discharge it at once, 

 it is evident that a much greater effect would be produced on an 

 external circuit, than by the slow, wire-drawn current from the 

 small terminals alone. 



Since the increase of conducting surface and the approxima- 

 tion of an uninsulated to an insulated conducting surface are one 

 and the same thiug, so far as electrical effects are concerned, the 

 Leyden jar furnishes the extreme condition of which this arrange- 

 ment is susceptible ; and we here find all that might be expected 

 from the sudden discharge of an accumulated quantity, moving 



