Any kind of dye found in nature can be made in the laboratory whenever its composition is understood and usually it can be made cheaper and purer than it can be extracted from the plant. But to work out a profitable process for making it synthetically is sometimes a task requiring high skill, persistent labor and heavy expenditure. One of the latest and most striking of these achievements of synthetic chemistry is the manufacture of indigo. Indigo is one of the oldest and fastest of the dyestuffs. To see that it is both ancient and lasting look at the unfaded blue cloths that enwrap an Egyptian mummy. When Caesar conquered our British ancestors he found them tattooed with woad, the native indigo. But the chief source of indigo was, as its name implies, India. In 1897 nearly a million acres in India were growing the indigo plant and the annual value of the crop was $20,000,000. Then the fall began and by 1914 India was producing only $300,000 worth! What had happened to destroy this profitable industry? Some blight or insect? No, it was simply that the Badische Anilin-und-Soda Fabrik had worked out a practical process for making artificial indigo. That indigo on breaking up gave off aniline was discovered as early as 1840. In fact that was how aniline got its name, for when Fritzsche distilled indigo with caustic soda he called the colorless distillate "aniline," from the Arabic name for indigo, "anil" or "al-nil," that is, "the blue-stuff." But how to reverse the process and get indigo from aniline puzzled chemists for more than forty years until finally it was solved by Adolf von Baeyer of Munich, who died in 1917 at the age of eighty-four. He worked on the problem of the constitution of indigo for fifteen years and discovered several ways of making it. It is possible to start from benzene, toluene or naphthalene. The first process was the easiest, but if you will refer to the products of the distillation of tar you will find that the amount of toluene produced is less than the naphthalene, which is hard to dispose of. That is, if a dye factory had worked out a process for making indigo from toluene it would not be practicable because there was not enough toluene produced to supply the demand for indigo. So the more complicated napthalene process was chosen in preference to the others in order to utilize this by-product.