Page:South African Geology - Schwarz - 1912.djvu/13

 DESCRIPTIVE GEOLOGY

Definition of Geology.—The Science of Geology is concerned with the study of the Mineral Kingdom, and therefore is a science parallel with Zoology and Botany, which are concerned respectively with the Animal and Vegetable Kingdoms. Like the two latter sciences, Geology deals with specimens—mineral or fossil species—which can be examined in the laboratory; but there is a far larger sub-section of the science which deals with specimens in the bulk, minerals aggregated into rocks, and rocks aggregated into land masses, continents, islands, mountains, and so forth; and all these must be considered in relation to the globe as a whole. A great part of Geology is thus concerned with vast masses which cannot be examined at leisure in the study, but which must be investigated in the field, and our ideas about them must be formed gradually as experience accumulates and our travels show us more and more of the diversities of the earth's surface. In this lies at once the disadvantage and the fascination of Geology. In our inability to see the whole of a mountain range or a continent, we formulate certain theories as to their 9