This has been generally acknowledged by the most philosophical naturalists of modern times. Thus Linnæus begins that part of his Botanical Philosophy in which names are treated of, by stating that the foundation of botany is twofold, _Disposition_ and _Denomination_; and he adds this Latin line, Nomina si nescis perit et cognitio rerum. {289} And Cuvier, in the Preface to his _Animal Kingdom_, explains, in a very striking manner, how the attempt to connect zoology with anatomy led him, at the same time, to reform the classifications, and to correct the nomenclature of preceding zoologists. I have stated that in Mineralogy we are still destitute of a good nomenclature generally current. From what has now been said, it will be seen that it may be very far from easy to supply this defect, since we have, as yet, no generally received system of mineralogical classification. Till we know what are really different species of minerals, and in what larger groups these species can be arranged, so as to have common properties, we shall never obtain a permanent mineralogical nomenclature. Thus _Leucocyclite_ and _Tesselite_ are minerals previously confounded with Apophyllite, which Sir John Herschel and Sir David Brewster distinguished by those names, in consequence of certain optical properties which they exhibit. But are these properties definite distinctions? and are there any external differences corresponding to them? If not, can we consider them as separate species? and if not separate species, ought they to have separate names? In like manner, we might ask if _Augite_ and _Hornblende_ are really the same species, as Gustavus Rose has maintained? if _Diallage_ and _Hypersthene_ are not definitely distinguished, which has been asserted by Kobell? Till such questions are settled, we cannot have a fixed nomenclature in mineralogy. What appears the best course to follow in the present state of the science, I shall consider when we come to speak of the form of technical terms. I may, however, notice here that the main Forms of systematic nomenclature are two:--terms which are produced by combining words of higher and lower generality, as the binary names, consisting of the name of the genus and the species, generally employed by natural historians since the time of Linnæus;--and terms in which some relation of things is indicated by a change in the form of the word, for example, an alteration of its termination, of which kind of {290} nomenclature we have a conspicuous example in the modern chemistry. APHORISM X. _New terms and changes of terms, which are not needed in order to express truth, are to be avoided._