Christian Friedrich Schoenbein to Faraday   25 November 1850

My dear Faraday

Will you be kind enough to forward the parcels inclosed to their places of destination.

There is no hurry in it, you may deliver them quite leisurely.

If you should happen to get the parcel with my sulphuret-papers it is very possible that those of lead have turned brown again. I see that by degrees sulphate of lead is acted upon by paper in the dark, so as to become brown i.e. sulphuret of lead.

I at least cannot account in another way for the fact that sulphuret of lead paper often having been completely bleached by ozonized or insolated oxigen turns gradually brown again in the dark.

The silhouettes laid by, which except the figures were once quite white will show you that action.

Yours | very truly | C.F. Schoenbein

Bâle 25, Nov. 1850.