What Dioscorides calls _Indicon_, and Pliny and Vitruvius _Indicum_, I am strongly inclined to believe to have been our indigo[615]. It was a blue pigment brought from India, and used both in painting and in dyeing. When pounded it gave a black powder, and when suspended in water it produced an agreeable mixture of blue and purple. It belonged to the costly dye-stuffs, and was often adulterated by the addition of earth. On this account, that which was soft without any roughness, and which resembled an inspissated juice, was esteemed the best. Pliny thinks[616] that pure indigo may be distinguished from that which is adulterated by burning it, as the former gives an exceedingly beautiful purple flame, and emits a smell similar to that of sea-water. Both he and Dioscorides speak of two kinds, one of which adheres to reeds, in the form of slime or scum thrown up by the sea; the other, as Dioscorides says, was scraped from the sides of the dye-pans in the form of a purple-coloured scum; and Pliny expressly remarks, that it was collected in this manner in the establishments for dyeing purple. The former relates also, that _Indicum_ belonged to the astringent medicines; that it was used for ulcers and inflammations, and that it cleansed and healed wounds. This is all, as far as I know, that is to be found in the works of the ancients respecting _Indicum_. I have given it at full length, as accurately as possible, and I have added, in order that the reader may be better able to compare and judge, references to the original words of the authors. _Indicon_, it is true, occurs in other passages; but it was certainly different from the one already mentioned. I allude, for example, to the black _Indicon_ of Arrian and the _Indicon_ of Hippocrates. Of the former I shall treat in particular hereafter; and in regard to the latter, I refer to the author quoted in the note below[617]. It is not at all surprising that these names should be applied to more Indian commodities, since at present we give to many kinds of fruit, flowers, fowls and other things, the appellation of Indian. The ancients, indeed, were not so careful as to distinguish always, by a proper addition, the many articles to which they gave the name of _Indica_; and they had reason to expect that their contemporaries would readily comprehend by the connexion, the kind that was properly meant. Their commentators, however, in later times have for the most part thought only of one species or thing, and by these means they have fallen into mistakes which I shall here endeavour to rectify.