I have long made it a rule, and prescribed it to others, in explaining any object mentioned by the ancients, never to admit, without the strongest proofs, that the same article is denoted by different appellations. This, it is true, has been often done. By these means the small knowledge we possess of a thing that occurs under one name only may be increased. A wider field may thus be opened for conjecture, and more latitude may be given to the imagination; but at the same time one may fall into groundless explanations, and hazard assertions, which, with whatever caution and learning proposed, will, on closer examination, be found either false or highly improbable. According to this rule, I have carefully endeavoured not to suffer myself to be so far misled by the respectability of my predecessors, as to consider the _Indicum_ and _Indicum nigrum_ of the ancients to be the same substance. On further research I find that the latter not only appears by the epithet to be different from indigo, but that it is China, or, as the Dutch call it, Indian ink. To prove this, I must refer to the passage of Pliny[627] on which my assertion is founded; and perhaps the short illustrations added will render this minuteness less tedious to those who are fond of such disquisitions. In the passage referred to, Pliny enumerates all the materials which in his time were used for black ink. He therefore mentions two vitriolic substances, a slime or sediment (_salsugo_), and a yellow vitriolic earth (called also _misy_). Such minerals continued in use as long as men were unacquainted with the art of lixiviating the salt, and causing it to crystallize; or in other words, as long as they had no vitriol-manufactories. He speaks also of lamp-black being made in huts built for the purpose, which are described by Vitruvius, and from which the smoke of burning pine-wood was conveyed into a close apartment. The article was certainly adulterated, when soot, taken from the baths and other places where an open fire was maintained with wood of all kinds, was intermixed with it. It is very remarkable that black from burnt refuse of grapes, _noir de vigne_, which at present our artists, and particularly our copper-plate printers, consider as the most beautiful black, was made even at that period. Germany hitherto has obtained the greater part of this article from Mentz, through Frankfort, and on that account it is called Frankfort black. Some is made also at Kitsingen, Markbreit, and Munich. For this purpose the refuse of the grapes is charred in a close fire, and being then finely pounded is packed into casks. Pliny observes, that it was asserted that from this substance one could obtain a black which might be substituted for indigo. Another pigment was bone-black, or burnt ivory, which is highly esteemed even at present. Besides these, continues he, there is obtained from India what is called _Indicum_, the preparation of which I have not yet been