It is found by experience, and particularly in hot climates, that substances containing _ammonia_ (volatile alkali) quite developed, have the property of raising and rendering more intense the red colours. It has been found, too, that the bones of animals retain the colour of _madder_ very strongly, when they have been given that colouring material; and the vivacity of the colour has been attributed in such cases, it is presumed with truth, to the ammonia which the bones contain. There are, therefore, in regard to _vegetables_ in particular, some things, the nature and properties of which it is absolutely necessary that the dyer should understand: for want of a knowledge of one of them, it is a fact that losses are very often sustained to a serious amount. It may seem surprising, but the author has not seen in any writer on dyeing or chemistry, a proper method of working the pastil or _woad vat_; nor how to renew and work it down, again and again, with an assurance that it will be neither decomposed nor spoiled; and which, for want of a proper knowledge, it has often been. We shall therefore endeavour to give some directions by which those fatal and expensive disasters may be avoided. Although, at first sight, it seems easy to distinguish the three kingdoms of nature from each other, yet there is such an imperceptible transition from one to the other, that it will be difficult to give such a definition as shall embrace all the individuals of each, and, at the same time, exclude those of the other kingdoms. On examination, indeed, we do find that there is in fact no natural distinction of this kind; and that there is scarcely a function common to vegetables and minerals which some of the animal tribe do not enjoy, and _vice versâ_. Yet it must, however, be noted, that most animals have the power of voluntary loco-motion, and are thus rendered peculiarly different from all other bodies which we find upon or in the earth. The substances constituting _vegetable_ differ from those constituting _mineral_ bodies, in their being of a more complex kind; and though vegetables are extremely susceptible of decomposition in various ways, not one can be, by any art, synthetically produced. Yet, although what are called by chemists the _proximate constituents of vegetables_ are numerous, such are _water_, _starch_, _sugar_, _gum_, _gluten_, _wax_, _oil_, _camphor_, _resins_, _colouring matter_, _extractive matter_, _several acids_, &c. &c. all of which are capable of being decomposed, the _ultimate constituents of vegetables_ are very few; the chief are _carbon_, _hydrogen_, and _oxygen_; some afford _nitrogen_; in some are traces of _sulphur_, _potassa_, _lime_, _soda_, _magnesia_, _silica_, &c.; in nearly all vegetables are traces of _iron_; in many _manganese_.