84 SECRETIONS. 



at the south. When the plant is about six months old, 

 these leaves are gathered and macerated in water, till 

 they begin to ferment ; they are then removed, and 

 the colouring material, which is extracted by the wa- 

 ter, is soon afterwards deposited. It is green^at first, 

 but in consequence of exposure to the atmosphere, it 

 gradually becomes blue. Similar to this is theWoad, 

 Isatis tinctoria, with which the ancient Britons stained 

 their bodies, that they might appear more terrible to 

 their enemies in battle. The culture of this plant has 

 been strongly recommended to the American farmer, 

 and as a dyeing material, it is scarcely inferior to the 

 preceding. 



RED colours exist in various plants. Madder, which 

 is obtained from the dried roots and stems of Rubia 

 tinctorum, is not only beautiful but very penetrating, 

 for it tinges the bones of animals, when mixed with 

 their food. From different species of Lichen a similar 

 colour is obtained ; and this is the origin of the Litmus, 

 much celebrated as the chemical test of alkalies and 

 acids. From the flowers of the Carthamus tinctorius^ 

 usually but improperly named Saffron, a red colour is 

 extracted, from which rouge is manufactured, by mix- 

 ing it with the powder of talc. The celebrated Cam- 

 peachy, and Brasil woods, whose names allude to the 

 countries from which they are imported, are well 

 known, and important colouring materials. 



YELLOW is also obtained from different plants, par- 

 ticularly from the bark of Quercitron, and some species 

 of Sumach. The Anatto of commerce, "is obtained 

 from the Bixa orellana, a tree that grows in South 

 America, and produces fruit twice in a year. The 

 seeds are bruised and kneaded with a little oil into a 

 paste, known by the name of rocou, from the decoction 



