At the creation of the earth every great continental division received (as every other organism has, regarded by itself, and not in relation to the greater whole of which it forms a part) its own special form. Each continent is like itself alone; its characteristics are not shared by any other. Each one was so planned and so formed as to have its own special function in the progress of human culture. This may be seen by reviewing the history of the past; this may fairly be suspected yet to be in the future. The individuality of each continent raises it to a place where its characteristics give it an independent character, and a capacity of development of itself, up to a certain point, but never beyond it. The continents are never to be regarded as high, dead masses of land, but as vital and effective instruments, working upon each other ceaselessly, and helping each other to attain the consummation intended in the counsels of the Divine Mind. The unity of the earth, the unity of the continents, the unity of every physical feature of the continents, and the building all up together in a perfect symmetry and mutual adaptation of parts, is the crowning thought of Geographical Science. The study of first causes has no less clear illustrations in the course of our investigations than elsewhere. It is the task of science to show the nature and mutual relations of all the subjects which fall within the scope of Natural History. The nature of the parts is only understood from a comprehension of the whole; not the reverse, however. That is a most just saying of Plato. The knowledge of the universal cannot proceed from a knowledge of the special. As the part is formed only in view of and on account of the whole, in its study, dissociated from the whole, it becomes a mere unit and independent existence. From understanding the solar system, we might arrive at a knowledge of the motion of the earth; and so, from a knowledge of the earth, we may advance to its continents, their relations, the characteristics of the different natural divisions, their subdivisions, their phenomena, and their living organization, embracing man, animals, and plants. The external formation of the globe, or what we may call the configuration of the continents, rests upon two characteristics—the horizontal and vertical dimensions. 1. The horizontal dimensions are designated by the sea-line boundary—the geographical limitation. 2. The vertical dimensions—the physical limitation—are defined by the elevation of terraces and highlands, and they exhibit the greatest diversity of phenomena.