George Biddell Airy to Faraday   30 October 1846

Royal Observatory Greenwich | 1846 October 30

My dear Sir

I have just that small degree of learning about galvanism which the wisdom of antiquity has declared to be peculiarly dangerous, and I therefore come to you for a finish of my education.

Some person has proposed (in a newspaper) to prevent the water kept in lead cisterns from conveying the salts of lead to the human stomach, by inserting, in the water kept in the cistern, plates of zinc, upon which the salts of lead, carbonates and others, will be quietly deposited.

Now I wish to ask you -

1. Does not the presence of the zinc vastly increase the action of these acids upon the lead?

2. Is it certain that all this increased amount of salts will be deposited on the zinc? or is it not possible that a larger amount than before may be left in the water to act injuriously on the drinkers?

I am my dear Sir | Yours very truly | G.B. Airy

Michael Faraday Esq | &c &c &c