Secondly, this disposition procures us the advantage of tracing the principles, from their source in the mineral kingdom, down to the last combinations into which they are capable of entering, that is, into animal matters; and of observing the successive alterations they undergo in passing out of one kingdom into another. Thirdly and lastly, I look upon the analysis of minerals to be the easiest of all; not only because they consist of fewer principles than vegetables and animals, but also because almost all of them are capable of enduring the most violent action of fire, when that is necessary to their decomposition, without any considerable change or diminution of their principles, to which those of other substances are frequently liable. Besides, I am not singular in this distribution of the three classes of bodies, which are the subjects of the chymical analysis: as it is the most natural, it has been adopted by several authors, or rather by most who have published Treatises of Chymistry. But there is something peculiarly my own in the manner wherein I have treated the analysis of each kingdom. In the mineral kingdom, for instance, will be found a considerable number of operations not to be met with in other Treatises of Chymistry; the authors having probably considered them as useless, or in some measure foreign, to the purpose of Elementary Books, and as constituting together a distinct art. I mean the processes for extracting saline and metallic substances from the minerals containing them. Yet, if it be considered that salts, metals, and semi-metals are far from being produced by nature in a state of perfection, or in that degree of purity which they are commonly supposed to have when they are first treated of in Books of Chymistry; but that, on the contrary, these substances are originally blended with each other, and adulterated with mixtures of heterogeneous matters, wherewith they form compound minerals; I imagine it will be allowed, that the operations by which these minerals are decomposed, in order to extract the metals, semi-metals, and other simpler substances, especially as they are founded on the most curious properties of these substances, are so far from being useless or foreign to the purposes of an Elementary Treatise, that they are, on the contrary, absolutely necessary thereto.