188 Dr. Wilson on the Decomposition of Water by Platinum. 



same, not that the intensity of the agent called into play, or 

 its mode of action is identical. If this could be affirmed, we 

 should be able to announce as a general proposition, that 

 manifestations of the same force absolutely identical as to 

 quality, quantity and intensity, could produce totally oppo- 

 site results, which would be tantamount to affirming that un- 

 like effects may flow from the same cause, without any altera- 

 tion in the qualities or conditions of the latter. 



The last observation I would make refers to the curious 

 fact noticed by Mr. Grove, namely, that when a platinum wire 

 is heated white-hot in steam, " in a few seconds a small bub- 

 ble of gas is formed; but if the action be continued for a 

 week, it does not increase in quantity *.^^ 



Are we to suppose that the wire is at the same time decom- 

 posing water around itself, and producing water at a little 

 distance, undoing in one place what it effects in another, so 

 that no permanent accumulation of gas is allowed to take 

 place ? This is possible, but I think not likely. The ob- 

 servation made by Mr. Grove seems sufficiently explicable, 

 on the supposition that as soon as the wire is completely en- 

 veloped in steam, the thermo-circulatory currents which the 

 high temperature occasions in the vapour prevent it from 

 remaining long enough in contact with the wire to become 

 heated white-hot. The steam probably circulates endlessly 

 around the wire without a trace of decomposition occurring 

 in it. It seems not unlikely indeed that in Mr. Grove's ex- 

 periments with his eudiometer it was not steam that yielded 

 the hydrogen and oxygen obtained, but the last film of water 

 below the wire, which could not escape from the metal, but 

 tended rather, in consequence of its expansion, to rise towards 

 it, and was thus compelled to acquire a white heat, and to 

 break up into its elements. If this view be correct, an ar- 

 rangement where a white-hot wire or sheet of platinum foil 

 was kept grazing the surface of water, might be found to 

 effect a continuous decomposition of the liquid in question. 



It is no objection to this view that an electric spark decom- 

 poses steam readily, for the duration of the spark is so short, 

 that there is no time for the production of thermo-currents, 

 nor any possibility of the steam escaping from the powerful 

 topical action of the discharge. The spark may be compared 

 to fulminating silver, whose action is instantaneous and vio- 

 lent, but quite local, — the heated platinum to gunpowder, the 

 effect of which is cumulative and more general. 



* Athenaeum, Sept. 19tli, 1846, p. 966. 



