The Second System of Berzelius, though not tenable in its rigorous form, approaches far nearer than any previous system to a complete character, bringing together like substances in a large portion of its extent. The System of Mohs also, whether or not unconsciously swayed by chemical doctrines, forms orders which have a community of chemical character; thus, the minerals of the order Haloide are salts of oxides, and those of the order Pyrites are sulphurets of metals. Thus the two methods appear to be converging to a common centre; and though we are unable to follow either of them to this point of union, we may learn from both in what direction we are to look for it. If we regard the best of the pure systems hitherto devised as indications of the nature of that system, perfect both as a chemical and as a natural-history system, to which a more complete condition of mineralogical knowledge may lead us, we may obtain, even at present, a tolerably good approximation to a complete classification; and such a one, if we recollect that it must be imperfect, and is to be held as provisional only, may be of no small value and use to us. The best of the mixed systems produced by this compromise again comes from Freiberg, and was published by Professor Naumann in 1828. Most of his orders have both a chemical character and great external resemblances. Thus his Haloides, divided into Unmetallic and Metallic, and these again into Hydrous and Anhydrous, give good natural groups. The most difficult minerals to arrange in all systems are the siliceous ones. These M. Naumann calls Silicides, and subdivides them into Metallic, Unmetallic, and Amphoteric or mixed; and again, into Hydrous and Anhydrous. Such a system is at least a good basis for future researches; and this is, as we have said, all that we can at present hope for. And when we recollect that the natural-history principle of classification has begun, as we have already seen, to make its appearance in our treatises of chemistry, we cannot doubt that some progress is making towards the object which I have pointed out. But we know not yet how far we are from the end. The combination of chemical, crystallographical, physical and optical properties into some lofty generalization, is probably a triumph reserved for future and distant years. Conclusion. The history of Mineralogy, both in its successes and by its failures, teaches us this lesson;-that in the sciences of classification, the establishment of the fixity of characters, and the discovery of such characters as are fixed, are steps of the first importance in the progress of these sciences. The recollection of this maxim may aid us in shap ing our course through the history of other sciences of this kind; in which, from the extent of the subject, and the mass of literature belonging to it, we might at first almost despair of casting the history into distinct epochs and periods. To the most prominent of such sciences, Botany, I now proceed. VOL. II.-23. Vatem aspicies quæ rupe sub altâ Fata canit, foliisque notas et nomina mandat. Behold the Sibyl !-Her who weaves a long, Unerring symbols and enduring names; For leaf on leaf a fitting place she finds; Their place once found, no more the leaves depart, But fixed rest :-such is her magic art. |