Of the other kinds of rubrica, those of Egypt and Africa are of the greatest utility to workers in wood, from the fact of their being absorbed with the greatest rapidity. They are used also for painting, and are found in a native state in iron-mines.[1876] CHAP. 16.—OCHRA: REMEDIES DERIVED FROM RUBRICA. It is from rubrica also, that ochra[1877] is prepared, the rubrica being burnt[1878] in new earthen pots well luted with clay. The more highly it is calcined in the furnace, the better the colour is. All kinds of rubrica are of a desiccative nature, and hence it is that they are so useful for plasters, and as an application even for erysipelas. CHAP. 17.—LEUCOPHORON. Half a pound of Pontic sinopis, ten pounds of bright sil,[1879] and two pounds of Greek melinum,[1880] well mixed and triturated together for twelve successive days, produce “leucophoron,”[1881] a cement used for applying gold-leaf to wood. CHAP. 18.—PARÆTONIUM. Parætonium[1882] is so called from the place[1883] of that name in Egypt. It is sea-foam,[1884] they say, solidified with slime, and hence it is that minute shells are often found in it. It is prepared also in the Isle of Crete, and at Cyrenæ. At Rome, it is adulterated with Cimolian[1885] earth, boiled and thickened. The price of that of the highest quality is fifty denarii per six pounds. This is the most unctuous of all the white colours, and the most tenacious as a coating for plaster, the result of its smoothness. CHAP. 19.—MELINUM: SIX REMEDIES. CERUSE. Melinum, too, is a white colour, the best being the produce of the Isle of Melos.[1886] It is found also in Samos; but this last kind is never used by painters, in consequence of its being too unctuous. The persons employed in extracting it, lie at full length upon the ground, and search for the veins among the rocks. In medicine it is employed for much the same purposes as eretria;[1887] in addition to which, it dries the tongue, acts as a depilatory, and has a soothing effect. The price of it is one sestertius per pound. The third of the white pigments is ceruse, the nature of which we have already[1888] explained when speaking of the ores of lead; there was also a native ceruse, formerly found on the lands of Theodotus at Smyrna, which the ancients made use of for painting ships. At the present day, all ceruse is prepared artificially, from lead and vinegar,[1889] as already stated. CHAP. 20.—USTA. Usta[1890] was accidentally discovered at a fire in the Piræus, some ceruse having been burnt in the jars there. Nicias, the artist above-mentioned,[1891] was the first to use it. At the present day, that of Asia, known also as “purpurea,” is considered the best. The price of it is six denarii per pound. It is prepared also at Rome by calcining marbled sil,[1892] and quenching it with vinegar. Without the use of usta shadows cannot be made.[1893] CHAP. 21.—ERETRIA.