1866. Manchester brown introduced, the second azo-colour; leading to the manufacture of sodium nitrite, and of dinitrobenzene. 1866. Iodine green introduced; leading to further use for methyl iodide. 1866. Diphenylamine blue introduced; leading to manufacture of diphenylamine. 1868. Blue shade of methyl violet introduced; leading to manufacture of benzyl chloride. 1868. Saffranine introduced. 1869. Nitrobenzene process for magenta discovered. 1876. Chrysoidine introduced, the third azo-colour. 1876. Methylene blue introduced; leading to manufacture of nitrosodimethylaniline. 1877. Acid magenta discovered. 1878. Methyl green introduced; leading to utilization of waste from beet-sugar manufacture. 1878. Malachite green discovered; leading to manufacture of benzoic aldehyde. 1878. Acid yellow discovered; leading to new use for aniline yellow. 1879. Neutral red and allied azines introduced; leading to a new use for nitrosodimethylaniline. 1883. Phosgene colours of rosaniline group introduced; leading to manufacture of phosgene. CHAPTER III. Among the most venerable of natural dye-stuffs is indigo, the substance from which Unverdorben first obtained aniline in 1826. The colouring matter is found in a number of leguminous (see Fig. 7), cruciferous, and other plants, some of which are largely cultivated in India, China, the Malay Archipelago, South America, and the West Indies; while others, such as woad (see Fig. 8), are grown in more temperate European climates. The tinctorial value of these plants was known in India and Egypt long before the Christian era. Egyptian mummy-cloths have been found dyed with indigo. The dye was known to the Greeks and Romans; its use is described by the younger Pliny in his Natural History. Indigo was introduced into Europe about the sixteenth century, but its use was strongly opposed by the woad cultivators, with whose industry the dye came into competition. In France the opposition was strong enough to secure the passing of an act in the time of Henry IV. inflicting the penalty of death upon any person found using the dye. The importance of indigo as an article of commerce is sufficiently known at the present time; more than 8000 tons are produced annually, corresponding in money value to about four million pounds. It is of importance to us as rulers of India to remember that the cultivation and manufacture of indigo is one of the staple industries of that country, from which the European markets derive the greater part of their supply. [Illustration: FIG. 7.--INDIGO PLANT (_Indigofera tinctoria_).]