Advanced textbook of physical geography Author:David Page Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: III. THE EARTH—ITS INDIVIDUAL STRUCTURE AND COMPOSITION. The Rooky Crust—Its Constitution and Formation. 24. Having considered in the preceding chapter ... more »some of the more obvious relations of the globe as a member of the Solar system, and the terms usually employed to express their connections, we now proceed to describe the leading features of its own special structure. As the knowledge of its general relations was derived chiefly from Astronomy, so a knowledge of its individual structure is mainly obtained from the teachings of Geology. As the one set of facts could be taught without going deeply into the problems of the astronomer, so the other may be understood without entering largely into the reasonings of the geologist. What, for instance, is the nature of the earth's rocky crust ? How are its rocks arranged, and how does this arrangement affect its superficial character? What has stretched out the level plain and upheaved the rugged mountain ? What renders one soil obnoxious and sterile, and another genial and fertile ? And as the earth's crust is continually undergoing modification under the operations of external and internal forces, what the effects of such modifications on the general geography of the globe ? These and similar problems geology endeavours to solve, and, with a little explanation, these solutions may be rendered intelligible to the student of Physical Geography. 25. Geologists speak of the "crust of the globe" just as the housewife talks of the " crust of her loaf." The crust of the loaf is one thing, the inside of it another. The crust or exterior portion of the earth, composed of rocks and rock-materials that can be seen and handled, is one thing ; the interior, of which we can know nothing by direct observation, may be, and in all likelihood...« less