The coal itself, as now universally admitted, is of vegetable origin. Under the microscope, in the most compact specimens, the tissues by which all the coal plants are more or less distinguished can be distinctly traced. Chemically considered, its vegetable origin is equally well established. Carbon constitutes the principal ingredient of the mineral the quality of which enters most abundantly into the composition of vegetables. One theory of its formation is, that vegetable matter, carried to the sea or extensive lakes, has undergone a process of decomposition, by which, while some of its principles may have escaped or been evolved in new combinations, the carbon, with a portion of the hydrogen, has remained; this, mixed with more or less earthy matter, has in its soft state been consolidated by the force of aggregation simply, or by compression from the superincumbent strata, and the action of a higher degree of temperature than now exists. Others are of opinion that coal is the altered residuum of trees and smaller plants that have grown on the spot where we now find them—that the forests were submerged and covered by detrital matter, which was upraised to form a foundation and a soil for another forest, to be in its turn submerged and converted into coal—and that thus the alternations which the vertical section of a coal-field exhibits are to be accounted for. The former views are maintained by Sir R. Murchison and other eminent geologists. The latter have been adopted by Sir Charles Lyell, in consequence mainly of the arrangements and structure observed in the remarkable coal-field of Nova Scotia, where he states that there is a range of perpendicular cliffs in the Bay of Fundy, composed of regular coal-measures, inclined at an angle between twenty-four and thirty degrees, whose united thickness is between four and five miles. By neither theory, perhaps, nor by any other yet advanced, is it possible to reconcile all the appearances which that singular compound, a COAL-FIELD exhibits—the various changes which the vegetable matter has undergone to convert it into lignite, jet, common coal, cannel coal, and anthracite, two or more of these varieties often occurring in the same coal-measures—in one quarter the clearest indications that the sea has let in its floods and mingled its spoils with those of the land, and in another quarter, through fourteen thousand feet, for example, of the drift accumulations in Nova Scotia, that there is not a trace even of any substance of a _marine_ character, all appearing to have been deposited in fresh water. But while no explanation yet given of the phenomena can be regarded as satisfactory, while Nature withholds much, and ever will, of the wonderful processes through which she attains her ends, the vegetable source of the product cannot be questioned; nay, the origin of coal from the extinct forests, from the trees and plants of a former age, is so very probable, that some beds