VOL. LXVIII.J PHILOSOPHICAL TRANSACTIONS. • 443 



a ball, and the middle of it resting in equilibrio on a pivot, on which it has a 

 free oscillation upwards and downwards ; if in this state a point is placed under 

 the end most distant from the prime conductor, the machine being then worked, 

 the other end will approach so near the prime conductor, as that the stream of 

 electricity will flow freely into it, as fast as it is produced by the action of the 

 wheel. In this case there will be no explosion ; and the reason is obvious, 

 because the 2d conductor, when it approaches so near the first as to form an 

 uninterrupted channel for the electric stream, becomes virtually a part of the 

 first. Hence the point operates on both together, just as it does when presented 

 directly to the prime conductor, that is, it steals away the electricity by little 

 and little, leaving not enough to give an explosion. When, instead of the point, 

 a polished ball is placed under the same end as before, this being less disposed to 

 receive the electric fluid, conveys away none of it; so that accumulating to a 

 certain degree on the prime conductor, it explodes on the contiguous end of the 

 2d, which, having a free oscillation, flies up with the stroke, and carries the 

 opposite end towards the ball, where, being saturated, it gives a snap ; the 

 recoil of which snap throws that end up, and the contrary end back towards the 

 conductor, and so on alternately, as long as the machine continues working. 



The event however is widely different when the 2d conductor, instead of 

 having a free oscillation, is screwed down in one place, and at such a distance 

 from the prime conductor, as not to receive the electric fluid till considerabi) 

 accumulated. For then the sharp point, previously opposed to its other end, 

 discharges it, as before observed, not in a continued stream and silently, but at 

 intervals, and with a strong explosion. 



The last of Mr. Nairne's experiments, and the only one yet unconsidered, is 

 that of the sharp point, which, being fixed to a kind of inverted pendulum, 

 oscillated with great velocity under the prime conductor, without receiving any 

 explosion. Now from this experiment I do not comprehend how any general 

 conclusion can possibly be drawn. It has been already shown, from the acknow- 

 ledgement of Dr. Franklin, and the experiments of Mr. Henly and Mr. 

 Nairne, that electricity, accumulated to a certain degree, will explode on a point. 

 If therefore, in any particular instance it does not explode, what can we infer 

 from it, but that the accumulation in every such instance was not sufficiently 

 great ; which may happen either from the smallness of the apparatus, or from 

 want of care in making the experiment. 



And now if we look back upon Mr. Nairne's experiments (which, by the bye, 

 have not all of them the merit of novelty) we shall find them to be nothing 

 more than different exemplifications of this well-known principle, that sharp 

 points, giving less resistance to the ingress of the electric fluid, will draw it off at 

 a greater distance than blunt or spherical terminations, and where the quantity 



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