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.

The Badische Anilin-und-Soda Fabrik spent $5,000,000 and seventeen years in chemical research before they could make indigo, but they gained a monopoly (or, to be exact, ninety-six per cent.) of the world’s production.  A hundred years ago indigo cost as much as $4 a pound.  In 1914 we were paying fifteen cents a pound for it.  Even the pauper labor of India could not compete with the German chemists at that price.  At the beginning of the present century Germany was paying more than $3,000,000 a year for indigo.  Fourteen years later Germany was selling indigo to the amount of $12,600,000.  Besides its cheapness, artificial indigo is preferable because it is of uniform quality and greater purity.  Vegetable indigo contains from forty to eighty per cent. of impurities, among them various other tinctorial substances.  Artificial indigo is made pure and of any desired strength, so the dyers can depend on it.

The value of the aniline colors lies in their infinite variety.  Some are fast, some will fade, some will stand wear and weather as long as the fabric, some will wash out on the spot.  Dyes can be made that will attach themselves to wool, to silk or to cotton, and give it any shade of any color.  The period of discovery by accident has long gone by.  The chemist nowadays decides first just what kind of a dye he wants, and then goes to work systematically to make it.  He begins by drawing a diagram of the molecule, double-linking nitrogen or carbon and oxygen atoms to give the required intensity, putting in acid or basic radicals to fasten it to the fiber, shifting the color back and forth along the spectrum at will by introducing methyl groups, until he gets it just to his liking.

Art can go ahead of nature in the dyestuff business.  Before man found that he could make all the dyes he wanted from the tar he had been burning up at home he searched the wide world over to find colors by which he could make himself—­or his wife—­garments as beautiful as those that arrayed the flower, the bird and the butterfly.  He sent divers down into the Mediterranean to rob the murex of his purple.  He sent ships to the new world to get Brazil wood and to the oldest world for indigo.  He robbed