The genera are established upon characters derived from all the parts of fructification compared together, according to their number, figure, proportion, and situation; but as this volume was intended to contain all the plants known to the author, the _natural_ characters thus formed could not be employed on account of their length, and he has used the _essential_ character, which is shorter, and consists of those marks that serve to distinguish the genera from each other in the natural orders; while at the head of each class, the genera are synoptically disposed, being defined by their _factitious_ characters, or those by which one is distinguished from another in the artificial order only. The remarks which we have already made respecting the generic and specific names, apply equally to this department. These last, in the systems of former botanists, were lengthened descriptions, taken from various circumstances, and seldom in any degree distinctive; but Linnaeus reduced them to twelve words at most, and derived them from some remarkable difference in the leaves, roots, stems, or other unvarying properties. These short phrases he continued to call the specific name, but they are now properly considered as the specific character; while he invented what he called the _trivial_ name, consisting of a single word added to the generic, and which we now use as the specific. The number of species mentioned in the Systema Naturae amounts to upwards of 7800. We come now to the third and last volume, containing his arrangement of the objects forming the mineral kingdom. This department has received less elucidation from him than the others. In 1736, he first digested a mineralogical system, in which he attempted to found the genera on definite characters; but he seems to have lost sight of the subject until obliged to attend to it when editing the twelfth edition of his work. There he prefixes to his arrangement a brief account of his theory on the origin of fossil bodies in general, and of their several combinations. His views, however, are extremely fanciful, and cannot be said to have produced any beneficial effect on the study of this science. As they have long ago passed into oblivion, it may afford amusement, if not instruction, to present an outline of them. The earth originated from water, agreeably to the testimony of Moses, Thales, and Seneca! The sea becoming pregnant gradually produced the dry land, from which the dew rose by evaporation, was elevated into clouds, and again descended in showers. No certain indications of a universal deluge have yet been found, but we every where perceive that land has been formed from the sea.