CHAPTER XLIII.
PHYSICAL GEOGRAPHY.—I. GEOLOGY.
GEOGRAPHY AND GEOLOGY—THE EARTH’S CRUST—ORIGIN OF THE EARTH—DENUDATION AND EXCAVATION BY WATER—ROCKS, GRAVEL, AND SAND—CLASSES OF ROCKS.
Fig. 636.—Cliffs worn by the sea.
When we were at school, and learnt the various countries of Europe, we had maps showing us the several divisions of one realm from another; the mountains, lakes, and other prominent features of the continent were learned and repeated, but we, maybe, seldom, perhaps never, bestowed a thought upon the formations of the mountains, and the manner in which rivers ran down into and through lakes to the ocean. There were the mountains, there were the lakes and rivers, and capes, and headlands, and there they are still, to all intents and purposes, the same to see, to climb up, to sail down, as the case may be. But the map of Europe has undergone a visible change. Territory has changed hands. Germany has gripped France, England has got Cyprus, Turkey has been dismembered, and Austria is annexing territory. This study is called Geography,—Political Geography,—for it marks the political boundaries. The knowledge of the formation of hills, headlands, lakes, rivers, seas, their causes, constitution, and effects, how they rose, how they exist and wax or wane during the course of centuries is Physical Geography, which we propose to consider.
This tree of knowledge includes some very important branches, almost parent stems. As a magnificent oak spreads forth its brawny arms, with smaller branches and twigs, each of these great branches being as large as an ordinary tree, so Physical Geography includes other arms such as Geology, Meteorology, Botany, and Physiology—even Astronomy in its comprehensive embrace. We find it is a difficult task to separate these kindred sciences from the great tree. We may have therefore to refer to earth, air, and water, and their various forms in hills and mountains, wind, vapour, rain, glaciers, and sea. We must learn how this earth has been gradually cooled, and what the various stages of its growth have done. We must consider plant and animal life upon our planet, and how the atmosphere affects them. All this is Physical Geography, and its satellite sciences of Geology, Meteorology, “Climatology,” Botany, and Physiology.
Fig. 637.—Disintegrated granite.
“Everything must have a beginning,” and the earth must have had a beginning, although the actual manner of the physical creation of the planet is a disputed fact. We are not about to discuss the religious side of the question, although we should undoubtedly find that Biblical and Geologic teaching run side by side towards the same end, and the testimony of the earth and sky bears witness to the Divine hand that created the universe, which we can trace back to the dim and distant ages when “the earth was without form and void, and darkness was upon the face of the deep.”
With this brief preface, let us consider some of these aspects, and pick up interesting facts from the ground.