skilfully and successfully, by the French chemists. The only thing left unexpressed by them was the exact proportion in which the elements were combined; and even this, since the establishment of the atomic theory, it has been found possible to express by a simple adaptation of their phraseology. But where the characters which must be taken into consideration in order sufficiently to designate the Kind, are too numerous to be all signified in the derivation of the name, and where no one of them is of such preponderant importance as to justify its being singled out to be so indicated, we may avail ourselves of a subsidiary resource. Though we cannot indicate the distinctive properties of the Kind, we may indicate its nearest natural affinities, by incorporating into its name the name of the proximate natural group of which it is one of the species. On this principle is founded the admirable binary nomenclature of botany and zoology. In this nomenclature the name of every species consists of the name of the genus, or natural group next above it, with a word added to distinguish the particular species. The last portion of the compound name is sometimes taken from some _one_ of the peculiarities in which that species differs from others of the genus; as Clematis _integrifolia_, Potentilla _alba_, Viola _palustris_, Artemisia _vulgaris_; sometimes from a circumstance of an historical nature, as Narcissus _poeticus_, Potentilla _tormentilla_ (indicating that the plant was formerly known by the latter name), Exacum _Candollii_ (from the fact that De Candolle was its first discoverer); and sometimes the word is purely conventional, as Thlaspi _bursa-pastoris_, Ranunculus _thora_; it is of little consequence which; since the second, or as it is usually called, the specific name, could at most express, independently of convention, no more than a very small portion of the connotation of the term. But by adding to this the name of the superior genus, we may make the best amends we can for the impossibility of so contriving the name as to express all the distinctive characters of the Kind. We make it, at all events, express as many of those characters as are common to the proximate natural group in which the Kind is included. If even those common characters are so numerous or so little familiar as to require a further extension of the same resource, we might, instead of a binary, adopt a ternary nomenclature, employing not only the name of the genus, but that of the next natural group in order of generality above the genus, commonly called the Family. This was done in the mineralogical nomenclature proposed by Professor Mohs. "The names framed by him were not composed of two, but of three elements, designating respectively the Species, the Genus, and the Order; thus he has such species as _Rhombohedral Lime Haloide_, _Octohedral Fluor Haloide_, _Prismatic Hal Baryte_."[22] The binary construction, however, has been