WOAD, or PASTEL, is obtained from a plant growing in various parts of Europe and also in this country; it is the _Isatis tinctoria_, and is cultivated with care for the dyeing matter which it affords, and which is obtained from the leaves of the plant, collected and prepared in a particular manner. Woad gives a full-bodied and fast blue to wool, yet not very bright, so that it is usually mixed with indigo[3]. Besides the preceding substances we may mention that _annatto_ is used for dyeing several colours; _kermes_, _madder_, and _Brazil wood_ for _reds_; _logwood_ for _purple_ and _black_; _peach-wood_ for _maroon_, &c.; _fustic_, _dyer's-broom_, _saw-wort_, _French-berries_, &c. for _yellow_; _walnut-root_, and the outside _green shell of the nuts_ for _browns_. We may also mention _prussiate of potash_, _acetate of lead_, commonly called _sugar of lead_, and _oxide of manganese_, as occasional articles used for various purposes by the dyer. Several other substances are also used in dyeing, which we cannot enumerate; some are mentioned in the subsequent pages. We may, however, name _cam-wood_, _bar-wood_, _redsanders_, and _myrobolans_. We ought also to observe that how desirable soever it may be to have all _woods_ for dyeing, in powder, in order to obtain the greatest quantity of colouring matter from them by decoction or otherwise, yet, as in a _powdered_ state they are much more likely to be adulterated than in _chips_, it is most advisable to purchase them in this last state; _logwood_ in particular ought never to be purchased in powder. _On the Component Parts of Vegetable and Animal substances._ In order more correctly to understand the theory and practice of dyeing, it is essential that the pupil should become acquainted with the nature of the substances upon which and with which he must necessarily operate. We shall not enter into the theories of _light_ and of _colours_, as propounded by Sir Isaac Newton, as well as many illustrious chemists, who have already done so much for the art of dyeing, but shall simply refer to such writers as URE, BANCROFT, BERTHOLLET, BRANDE, &c. from whom may be learnt what is of most importance to be known concerning this curious subject.