This section is from the book "Chromatography; Or, A Treatise On Colours And Pigments, And Of Their Powers In Painting", by George Field. Also available from Amazon: Chromatography, or A Treatise on Colours and Pigments, and of Their Powers in Painting.
Cologn Earth, incorrectly called Culteris-earth, is a native pigment, darker than the two last, and in no respect differing from Vandyke brown in its uses and properties as a colour. Similar earths abound in our own country. They are all bituminous ochres.