Previous to the year 1856 the colouring matters derived from coal-tar were practically unknown. Until then, that black evil-smelling substance was looked upon as almost worthless; but gradually the unsightly grub emerged into a beautiful butterfly, clothed first in mauve and next in magenta. After its long winter of neglect, there sprung from coal-tar the most vivid and varied hues, like flowers from the earth at spring. At a touch of the fairy wand of science, the waste land became a garden of tropic tints, and colour succeeded colour, until the whole gamut had been gone through. Never was transformation more dazzling or more complete. The once despised refuse was now a valued commercial product--indeed a trade in itself. Perfectly fascinated by the study, chemists threw themselves heart and soul into coal-tar, and coal-tar colours were to be seen everywhere. It were beside our purpose to enter into the various stages through which coal has to pass to become colour. Enough to state that to the introduction of gas-light we are indebted for the acquisition of coal-tar colours, the starting point for the production of mauve, magenta, &c., being the manufacture of coal-gas. From the destructive distillation of coal, coal-tar oil results; and from this are obtained the products which yield the colours in question. Among these products may be mentioned aniline, rosaniline, napthaline, chinoline, carbolic acid, picric acid, &c., with their derivatives. Of the fifty-one compounds furnished by the distillation of coal, perhaps the most popularly associated with coal-tar colours is aniline, to which we will therefore confine ourselves. Discovered in 1826, this body was formerly prepared from indigo--in Spanish, _anil_, whence the name; but is now produced on a larger scale from benzol, a coal-tar product. As the source of mauve and magenta, aniline must be considered the parent of coal-tar colours generally. Little was known of it at one time except that on being mixed with a solution of chloride of lime there was formed a splendid purple liquid, which immediately gave place to a dingy reddish precipitate. From the investigation of this simple fact, however, by Mr. W. Perkin, there was created a new and important branch of chemical industry--the manufacture of coal-tar colours. The violet mauve led the way, followed by the red magenta, the blue azuline, the yellow phosphine, the green emeraldine, the orange aurine, by purple, and brown, and black. Such were the hues, with many intermediate tints and shades, which one reaction brought forth. The world rubbed its eyes with astonishment; and truly it seemed almost as wonderful to produce the colours of the rainbow from a lump of coal, as to extract sunshine from cucumbers.