7. The question here offers itself, whether this Idea of Natural Affinity is applicable to inorganic as well as to organic bodies;—whether there be Natural Affinities among Minerals. And to this we are now enabled to reply by considering whether or not the principle just stated is applicable in such cases. And the conclusion to which our principle leads us is,—that there are such Natural Affinities among Minerals, since there are different sets of characters which may be taken, (and have by different writers been taken,) as the basis of classification. The hardness, specific gravity, colour, lustre, crystallization, and other external characters, as they are termed, form one body of properties according to which minerals may be classified; as has in fact been done by Mohs, Breithaupt, and others. The chemical constitution of the substances, on the other hand, may be made the principle of their arrangement, as was done by Haüy, and more recently, and on a different scheme, by Berzelius. Which of these is the true and natural classification? To this we answer, that each of these arrangements is true and natural, then, and then only, when it coincides with the other. An arrangement by external characters which gives us classes possessing a common chemical character;—a chemical order which brings together like and separates unlike minerals;—such classifications have the evidence of truth in their agreement with one another. Every classification of minerals which does not aim at and tend to such a result, is so far merely arbitrary; and cannot be subservient to the expression of general chemical and mineralogical truths, which is the proper purpose of such a classification.
8. In the History of Mineralogy I have related the advances which have been made among mineralogists and chemists in modern times towards a System [165] possessing this character of truth. I have there described the mixed systems of Werner and Haüy;—the attempt made by Mohs to form a pure Natural History system;—the first and second attempt of Berzelius to form a pure chemical system; and the failure of both these attempts. But the distinct separation of the two elements of which science requires the coincidence threw a very useful light upon the subject; and the succeeding mixed systems, such as that of Naumann, approached much nearer to the true conditions of the problem than any of the preceding ones had done. Thus, as I have stated, several of Naumann’s groups have both a common chemical character and great external resemblances. Such are his Anhydrous Unmetallic Haloids—his Anhydrous Metallic Haloids—Hydrous Metallic Haloids—Oxides of metals—Pyrites—Glances—Blendes. The existence of such groups shows that we may hope ultimately to obtain a classification of minerals which shall be both chemically significant, and agreeable to the methods of Natural History: although when we consider how very imperfect as yet our knowledge of the chemical composition of minerals is, we can hardly flatter ourselves that we shall arrive at such a result very soon.
We have thus seen that in Mineralogy, as well as in the sciences which treat of organized bodies, we may apply the Idea of Natural Affinity; of which the fundamental maxim is, that arrangements obtained from different sets of characters must coincide.
Since the notion of Affinity is thus applicable to inorganic as well as to organic bodies, it is plain that it is not a mere modification of the Idea of Organization or Function, although it may in some of its aspects appear to approach near to these other Ideas. But these Ideas, or others which are the foundation of them, necessarily enter in a very prominent and fundamental manner into all the other parts of Natural History. To the consideration of these, therefore, we shall now proceed.
BOOK IX.
THE
PHILOSOPHY
OF
BIOLOGY.
La vie est donc un Tourbillon plus ou moins rapide, plus ou moins compliqué, dont la direction est constante, et qui entraine toujours des molecules de mêmes sorts, mais où les molecules individuelles entrent et d’où elles sortent continuellement, de manière que la Forme du corps vivant lui est plus essentielle que sa Matière.
Tant que ce mouvement subsiste, le corps où il s’exerce est vivant; il vit. Lorsque le mouvement s’arrête sans retour, le corps meurt.