What may in the largest and most general sense be called the superficies of the earth, is threefold in character, and yet one in function; consisting of a highly elastic body, the atmosphere, water, and the solid ground. These three forms are variously proportioned; the more elastic is universal, the fluid form is more restricted, and the solid one prevails still less. The more dense the body, the nearer it is found to the center of the earth. The lightest of all floats over the entire periphery of the globe like a graceful mantle of cloud. Man, and in fact all organisms, live by contact with all three of these forms. The investigation of the elements, and phenomena of the air, _regarded in themselves_, is the province of meteorology. The mercury-column is the true language of the atmosphere, and tells us in distinct tones of all the changes there. Mineralogy and geology make us acquainted with all the qualities and all the elements of the soil, not in their relation to man, but regarded in themselves. Geography deals with the conflict of all these bodies, their relations to each other, their mutual action and reaction. Meteorology gives occasion for the study of climate, and for the observation of the phenomena of the lower strata of the atmosphere,—the fall of rain and snow, for example. Geology and mineralogy give rise to the study of plains and mountain formations, as well as of volcanic phenomena, affecting the surface of the earth as they do in earthquakes, upheavals of whole districts, and the opening of hot springs. Thus, geography has it own province clearly defined, and uses all this and studies it in relation to the organic world, and to man foremost of all. The most highly elastic covering of the earth is unbroken, the other two are sundered, and each only occupies a part of the surface. Formerly, in most ancient times, the water seems to have covered the entire earth. The study of this is, however, within the domain of geology. We have to do only with the historic period which followed. We have to look at the earth in its present relations, and as the home of man. Now, the portions covered with water are, by far, the largest part of the surface; a little less than three-fourths are water, a little more than one-fourth land. The whole water-mass is composed largely of the oceans, which, in one sense, constitute a continent of their own: in looking at them as we do now, we are not to regard them as ceasing at the outlines of the great land-masses, but as penetrating these as far as to the springs which feed the rivers; for the world of waters, embracing springs, brooks, rivers, lakes, seas, and oceans, is one, and but one.