Page:South African Geology - Schwarz - 1912.djvu/10

 example, the Planetismal Hypothesis. As this is accepted all over America, and is taught in at least two universities in England, I could not in justice to the science insert the old exploded Nebular Hypothesis, with its mediaeval visions of fire and brimstone. Brun's work on volcanoes is still in the expensive French edition, and is unknown to most geologists, yet his work is too thorough to permit of doubt but that the steaming-volcano people are wrong. In the case of the igneous rocks I have allowed myself to dilate on the absorption of sedimentary rocks in defiance of ex cathedra statements that basic selvages to laccolites are due to magmatic differentiation; but here I have such unmistakable proofs that my reading is correct that it would be misleading to instruct the South African student otherwise, when by looking out of the railway carriage he can see for himself the facts of the case. In the stratigraphical part I have been guided by the present state of the geological surveys, and have put in all the separate systems of Pal-Afric rocks, though I believe that half of them are only modifications of the other half. Teachers will have to indicate where their views differ from mine, but the scheme here presented will, I think, help the student to grasp the main principles better than a mere cataloguing of isolated facts.

Some people collect postage stamps, others, called geologists, collect facts and docket and label them with an intelligence equal to that devoted by the stamp collectors to their subject. My book will be of very little use to those who wish to become scientists of this kind. I have endeavoured to describe the facts as far as possible in relation to their causes, and to give some insight into the processes of geological reasoning. I have used the simplest possible language, because I hope that the book may fall into the hands of many people who, though not skilled in all the intricacies of scientific nomenclature, take an interest in nature and have a longing for a better understanding of the glories of this wonderful land of South Africa.