Parætonium[1] is so called from the place[2] of that name in Egypt. It is sea-foam,[3] 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[4] 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.