It may be pointed out that the greatest confusion exists in the nomenclature of pigments, to such an extent that, in many cases, neither the chemist nor the manufacturer knows precisely what pigment is implied by a given name. The confusion is still further increased by the use of names taken from different languages. TRUE UMBER Umber, properly so called--also known as Turkish, Cyprian or Sicilian umber, from the country of origin--derives its name, according to some authorities, from the province of Umbria (Italy), where a brown earth is found, though others ascribe it to the Latin “umbra” (shade) because of the pigment being used for painting shadows. True umber is an earthy mass of fine texture and liver-brown colour, merging into chestnut in some of the lumps. Chemically, it consists of a double silicate of iron and manganese combined with water, a portion of these metals being usually replaced by alumina. The greater hardness (1·5) and higher specific gravity (2·2) of true umber in comparison with Cologne earth (which is quite arbitrarily termed “umber”), form a ready means of differentiation between the two. According to Viktor Merz, the umber found in Cyprus consists of: ferric oxide, 52%; manganese oxide, 14·5%; and alumina, 3%; and is, possibly, merely a mixture of clay with hydroxide of iron or manganese. An umber examined by Klaproth contained 13% of silica, 5% of alumina, 48% of ferric oxide, 20% of manganese oxide and 14% of water. The tone of umber can be modified, in the direction of red, by calcination, but this process is seldom employed, the dark brown shade of this colour being the one most appreciated. In some parts of northern Germany, Thuringia in particular, the iron mines contain smaller or larger pockets of ferric hydroxide, of a fine earthy texture, from which umber is prepared, by levigation and calcination. The product is sold under various names: chestnut brown, wood brown, mahogany brown, bistre flea brown, roe brown, according to the shade of the calcined pigment. A mineral (“siderosilicate,” according to Von Walterhausen) composed of ferric silicate, and approximating in this respect to terra di Siena, is found in the neighbourhood of Passaro (Sicily) in deposits of tuff. It forms masses which are transparent at the edges and are usually liver-brown to chestnut in colour. The hardness of the mineral is 2·5, the sp. gr. 2·713, and the average chemical composition: silica, 34%; ferric oxide, 48·5%; alumina, 7·5%; and water, 10%.