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copper. The white lead is roasted in a furnace, and,by the action of the fire, becomes red lead. This inven-tion was the result of observation in the case of anaccidental fire; and, by the process, a much bettermaterial is obtained than that which is procured frommines.

CHAPTER XIII.

OF PURPLE.

I shall now speak of purple, which, above all othercolours, has a delightful effect, not less from its raritythan from its excellence. It is procured from the marineshell which yields the scarlet dye, and possesses quali-ties not less extraordinary than those of any other bodywhatever. It does not in all places where it is foundpossess the same quality of colour ; hut varies in thatrespect according to the sun’s course. Thus, that whichis obtained in Pontus and in Galatia, from the nearnessof those countries to the north, is brown; in thosebetween the south and the west, it is pale; that whichis found in the equinoctial regions, east and west, is of aviolet hue; lastly, that which comes from southerncountries possesses a red quality: the red sort is alsofound in the island of Rhodes, and other places near theequator. After the shells are gathered they are brokeninto small pieces with iron bars; from the blows ofwhich, the purple dye oozes out like tears, and is drainedinto mortars and ground. It is called ostrum, becauseextracted from marine shells. Inasmuch as this colour,from its saltness, soon dries, it is prepared for use withhoney.