Jens Jacob Asmussen Worsaae,
The Primeval Antiquities of Denmark…
(1849)
“ Silver usually assumes a blackish tinge. Bronze and copper in peat bogs obtain a red or blackish tint; while in the earth they usually become green. Iron, of course, becomes very rusty indeed, except in the peat bogs. Lead becomes oxydized; amber acquires a resemblance to resin, by lying in the earth; glass becomes covered with a thick coating and looks like mother of pearl. Bones are calcined, and become brown in the bogs, where they are always best preserved. Nevertheless, antiquities should never be cleaned, for they are injured by this means, and so lose much of their value. ”
