Formerly, Geography was regarded as a mere auxiliary of History, Politics, Military Science, Natural History, the Industrial Arts, and Commerce. And in truth it does reach out and teach all these departments of knowledge and action; but only in the most recent times has it assumed the place of an independent branch of study. Only through the widening of the whole circle of sciences has room been made for this. Geography used, for the sake of commerce, to be divided into three divisions: mathematical, physical, and political. This was at the time when it was thought that the whole frame-work of the sciences was a disjointed and sundered thing; before that minor principle of unity which binds them all together was recognized as one of the noblest conceptions that the mind can cherish. In the first two of these arbitrary divisions into which Geography was severed, the relations of astronomy, mathematics, and physics were studied, and their applications to the confused phenomena of the globe investigated. Yet the most important thing of all escaped notice; students overlooked their chief task, the tracing of causation and interdependence in the phenomena, and the relation of every one to the country which supplies its conditions of being. It was not suspected that each phenomenon was one link of a great chain of phenomena, the whole revealing a comprehensive law. Men discussed porphyritic formations, basaltic columns, hot springs, and a thousand features which dot the earth, and a thousand kinds of rock which rift the surface of the globe, and treated them singly as if each was a spore and the whole combination only a sporadic group. They did not discover that in the one feature was to be found the reason of the existence of its neighbor; that all the layers of stone owe their singularities of structure to one another rather than to themselves; that each one stands in the closest connection with the upheaval of the loftiest mountains, with the formation of great volcanic islands, and, in truth, with the building up of entire continents. And, in like manner, plants were discussed as if they were obedient to no law of grouping, as if they were scattered broadcast over the earth, having no relation to zones of vegetation, to isothermal and isochimenal lines; as if, in fact, there was no suspicion of any principle underlying the very existence of the whole vegetable kingdom. And so, too, with such phenomena as the Aurora Borealis; they were treated as isolated features, rather than in their relations to the globe; the connection was not seen between the maritime discoveries of voyagers and the great system of oceanic currents, on which voyagers are so dependent; in fact, the whole influence of the world of matter on the world of mind was unexplored.