=The study of earth features and their significance.=—The features upon the surface of the earth have all their deep significance, and if properly understood, a flood of light is thrown, not only upon present conditions, but upon many chapters of the earth’s earlier history. Here the relation of our study to topography and geography is very close, so that the lines of separation are but ill defined. The terms “physiographical geology”, “physiography”, and “geomorphology” are concerned with the configuration of the earth’s surface—its physiognomy—and with the genesis of its individual surface features. It is this genetical side of physiography which separates it from topography and lends it an absorbing interest, though it causes it to largely overlap the division of dynamical geology or the study of geological processes. In fact, the difference between dynamical geology and physiography is largely one of emphasis, the stress being laid upon the processes in the former and upon the resultant features in the latter. Under dynamical geology are included important subdivisions, such as seismic geology, or the study of earthquakes, and vulcanology, or the study of volcanoes. Another large subject, glacial geology, belongs within the broad frontier common to both dynamical geology and physiography. A relatively new subdivision of geological science is orientational geology, which is concerned with the trend of earth features, and is closely related both to physiography and to dynamical and structural geology. =Tabular recapitulation.=—In a slightly different arrangement from the above order of mention, the subdivisions of geology are as follows:— _Subdivisions of Geology_ _Petrographical Geology._ Materials of the earth. _Geotectonic Geology._ Architecture of the earth’s outer shell. _Dynamical Geology._ Earth processes. Seismic Geology—earthquakes. Vulcanology—volcanoes. Glacial Geology—glaciers, etc. _Physiographical Geology._ Earth physiognomy and its genesis. _Orientational Geology._ The arrangement and the trend of earth features. In one way or another all of the above subdivisions of geology are in some way concerned in the genesis of earth physiognomy, and they must therefore be given consideration in a work which is devoted to a study of the meaning of earth features. The compiled record of the rocks is, however, something quite apart and without pertinence to the present work. As already indicated its subdivisions are:—