Page:Lifelettersoffaradayjonesvol1.djvu/39

1812.
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Æt. 20-1.

dense—white cloud of matter descended from the positive wire, and bubbles rose rapidly and in quick succession from the negative wire; but after a time I perceived that the action slackened: the white cloud was scarcely perceptible at the wire, though by the former action the lower part of the solution was perfectly opaque and the bubbles nearly ceased. I thought that the action of the battery was exhausted; but in philosophy we do not admit suppositions; and therefore, to prove whether the battery was inert, or whether any principle in the water was exhausted, I substituted a fresh portion of water for that which had been galvanised. Then the action commenced again, and went on as at first. The white precipitate again appeared, and bubbles rose as before; but after a while it ceased, as in the first instance.

'I make no affirmative conclusion from these phenomena, but this I presume, that the water was not decomposed. Our water comes through iron pipes, and is retained in a leaden cistern. I have also ascertained that it holds a small portion of muriatic acid, and have no doubt that it contains carbonic acid. Now, do you think that any part of the lead or iron (the lead I should rather fancy) is held in solution by the muriatic or carbonic acid, and that the bubbles are formed by the precipitation of the metal, whilst the acid—what a blunder! I mean that the bubbles are formed by the escape of the acid and the precipitate—is the metallic oxide? Explain this circumstance to me—will you?—either by your pen or your tongue. Another phenomenon I observed was this: on separating the discs from each other, I found that some of the zinc discs had got a coating—a very superficial one in some