TOL. XLV.] PHILOSOPHICAL TRANSACTIONS. 455 



as from small ones under the same circumstances, will not be considerable, un- 

 less the circuit be completed ; that is, unless some matter, non-electnc in a con- 

 siderable degree, and in contact with the coatings of the phials, is brought into 

 contact, or nearly so, with such non-electrics as communicate with the matter 

 contained in the phials themselves. When indeed the circuit can be completed, 

 the explosion from the large glasses is prodigious; the whole quantity of electri- 

 city accumulated, or nearly so, being discharged in an instant. But the fact is 

 otherwise if the circuit is not completed, and the iron rod in the mouth of one 

 of these phials is touched by a non -electric (the hand of a man for instance) not 

 in contact with the tail wire : for then there will be no explosion, no shock ; but 

 the person approaching his finger near the iron rod, will see a succession of small 

 sparks, more intensely red than that large one seen when the phials explode at 

 once ; and the person making the experiment will feel a very pungent pain, but 

 confined to that finger which touches the iron rod. This succession of sparks 

 continues till the electricity accumulated in the phials is nearly exhausted. So 

 that the explosion from any given quantity of electricity, accumulated as before- 

 mentioned, is greater or less in proportion to the time expended in making that 

 explosion: in like manner as a given quantity of grained gunpowder rammed 

 hard in a pistol, is almost instantaneously fired, and that with a great report; 

 when the same quantity of gunpowder rubbed fine, and rammed hard, takes 

 a considerable time in burning as a squib, and makes no explosion. 



From what he has advanced, it may possibly be conjectured, that the electrical 

 effluvia occupy only the surfaces of bodies electrised; as we found that a very 

 small quantity of matter, distributed under a very large surface, would occasion 

 a greater accumulation of electricity, than a much more considerable quantity of 

 matter under a less. But that the electricity occupies the whole masses of bodies 

 electrised, and passes through their constituent parts, Mr. W. thinks is clearly 

 demonstrated by the following experiments. 



He enveloped an iron rod, about 3 feet in length, with a mixture of wax and 

 resin, leaving free from this mixture only one inch at each end. This iron was 

 warmed, when thus fitted, that the whole of its surface where it was intended 

 might be covered. This rod, when electrised at one of its ends, snapped as 

 strongly at the other, as though it was without the wax and resin. This could 

 not have happened from the electricities passing along the surface of the iron rod, 

 because there it was prevented by the originally electrics, and consequently must 

 of necessity pass through it. — Again, a phial of water in the experiment of Ley- 

 den can be electrised, and may be caused to explode, though the wire, touching 

 the water in the phial in making that experiment, be run through a wax stop- 

 ple, exactly fitted to the mouth of the phial. 



He caused a glass tube, open at each end, and about 2 feet and a half long, 



