Not the least romantic chapter of coal-tar chemistry is this production of fragrant perfumes from the evil-smelling tar. Be it remembered that these products--which Nature elaborates by obscure physiological processes in the living plant--are no more contained in the tar than are the hundreds of colouring-matters which have been prepared from this same source. It is by chemical skill that these compounds have been built up from their elemental groups; and the artificial products, as in the case of indigo and alizarin, are chemically identical with those obtained from the plant. Among the late achievements in the synthesis of vegetable products from coal-tar compounds is that of juglone, a crystalline substance found in walnut-shell. It was shown by Bernthsen in 1884 that this compound was hydroxy-naphthaquinone, and in 1887 its synthesis from naphthalene was accomplished by this same chemist in conjunction with Dr. Semper. Another recent development in the present branch of chemistry brings a coal-tar product into competition with sugar. In 1879 Dr. Fahlberg discovered a certain derivative of toluene which possessed an intensely sweet taste. By 1884 the manufacture of this product had been improved to a sufficient extent to enable it to be introduced into commerce as a flavouring material in cases where sweetness is wanted without the use of sugar, such as in the food of diabetic patients. Under the name of "saccharin," Fahlberg thus gave to commerce a substance having more than three hundred times the sweetening power of cane-sugar--a substance not only possessed of an intense taste, but not acted upon by ferments, and possessing distinctly antiseptic properties. The future of coal-tar saccharin has yet to be developed; but its advantages are so numerous that it cannot fail to become sooner or later one of the most important of coal-tar products. In cases where sweetening is required without the possibility of the subsequent formation of alcohol by fermentation, saccharin has been used with great success, especially in the manufacture of aerated waters. Its value in medicine has been recognized by its recent admission into the Pharmacopoeia. The remarkable achievements of modern chemistry in connection with coal-tar products do not end with the formation of colouring-matters, medicines, and perfumes. The introduction of the beautiful dyes has had an influence in other directions, and has led to results quite unsuspected until the restless spirit of investigation opened out new fields for their application. A few of these secondary uses are sufficiently important to be chronicled here. In sanitary engineering, for example, the intense colouring power of fluorescein is frequently made use of to test the soundness of drains, or to find out whether a well receives drainage from insanitary sources. In photography also coal-tar colouring-matters are playing an important part by virtue of a certain property which some of these compounds possess.