450 Mr. M. Donovan on the supposed Identity of the Agent 



circuit. The polar wires are in contact with the two coatings of 

 the jars ; the two coatings are therefore now the real polar con- 

 ductors, notwithstanding their extensive surface ; but they are not 

 in contact, for they are surrounded on all sides by an insuperable 

 barrier of glass ; they are in fact perfectly insulated. How is it 

 possible that the Leyden battery can, under such circumstances, 

 receive from an unclosed circuit a charge of what has a title to 

 be considered the true current of the voltaic agent, and which 

 can only circulate in the closed current ? 



The state of the case appears to be this. The opinion here 

 impugned is, that the current is the condition of voltaic electri- 

 city which produces the phenomena, and that it consists of an 

 enormous quantity of electricity in rapid flow. One of the 

 proofs offered is, that a Leyden battery receives an immediate 

 charge from a connexion with the voltaic series. But it has just 

 been shown, that, during this connexion with the voltaic series, 

 the current does not exist ; hence the charge of the Leyden 

 battery cannot be derived from it ; and were the charge ever so 

 great, it would prove nothing relative to the current. The 

 charge merely shows that, in the unclosed circuit, free electricity 

 is present, but that its quantity, at any moment, is in a position 

 which even the supporters of the hypothesis in question deny, 

 and justly, since it appears that the experiments of Sir H. Davy, 

 Van Marum, Professor E. Davy and myself with the Leyden 

 battery, evince that the quantity in the unclosed circuit is incon- 

 siderable. 



Indeed, it appears difficult to account for the shock given by 

 a voltaic series at all according to received opinions. The shock 

 of one or two thousand pairs of plates is tremendous and over- 

 powering. The intensity is admitted to be exceedingly feeble, 

 but the quantity is affirmed to be very great, and to its efficacy 

 the shock is attributed. Abstracting from all other objections, 

 the following seems to be of no small force. 



That intensity is the efficient condition of electricity for 

 giving a shock is shown by all known facts. If a person place 

 one hand on the negative conductor of the largest electric ma- 

 chine, and his other hand on the positive one, the utmost power 

 of the machine will not cause any sensation. But let him remove 

 one hand to a distance of ten or twelve inches, retaining the other 

 in its place, and he will obtain crooked sparks, every one of which 

 will amount to a severe shock. At the distance of three or four 

 inches he will be struck by a torrent of sparks which will be ab- 

 solutely intolerable, if the electric machine possess great power. 

 Yet here, the quantity of electricity is the same as when the two 

 hands touched the conductors, but the intensity is very different : 

 intensity gave powerful shocks, quantity did nothing. The in- 



