Note 1904 — BOOK XXXV. AN ACCOUNT OF PAINTINGS AND COLOURS.
John Bostock translation
“Carbones infectos.” The reading is very doubtful. It may possibly mean “charred bones tainted with dirt.” This would make an inferior ivory-black. The earth before-mentioned is considered by Ajasson to be a deuto-sulphate of copper, a solution of which, in gallic acid, is still used for dyeing black. The water near copper-mines would very probably be also highly impregnated with it. Beckmann considers these to have been vitriolic products. Vol. II. p. 265.