classes are again variously subdivided: thus the Terrains Yzemiens are _Thalassiques_, _Pelagiques_, and _Abyssiques_; and the Abyssiques are subdivided into _Lias_, _Keuper_, _Conchiliens_, _Pœciliens_, _Peneens_, _Rudimentaires_, _Entritiques_, _Houillers_, _Carbonifers_ and _Gres Rouge Ancien_. Scarcely any amount of new truths would induce geologists to burthen themselves at once with this enormous system of new names: but in fact, it is evident that any portion of truth, which any author can have brought to light, may be conveyed by means of a much simpler apparatus. Such a nomenclature carries its condemnation on its own face. Nearly the same may be said of the systematic nomenclature proposed for mineralogy by Professor Mohs. Even if all his Genera be really natural groups, (a doctrine which we can have no confidence in till they are confirmed by the evidence of chemistry,) there is no {293} necessity to make so great a change in the received names of minerals. His proceeding in this respect, so different from the temperance of Linnæus and Cuvier, has probably ensured a speedy oblivion to this part of his system. In crystallography, on the other hand, in which Mohs's improvements have been very valuable, there are several terms introduced by him, as _rhombohedron_, _scalenohedron_, _hemihedral_, _systems_ of crystallization, which will probably be a permanent portion of the language of science. I may remark, in general, that the only persons who succeed in making great alterations in the language of science, are not those who make names arbitrarily and as an exercise of ingenuity, but those who have much new knowledge to communicate; so that the vehicle is commended to general reception by the value of what it contains. It is only eminent discoverers to whom the authority is conceded of introducing a new system of names; just as it is only the highest authority in the state which has the power of putting a new coinage in circulation.