PREFACE IN the ten years spent on the Geological Survey of the Colony of the Cape of Good Hope I was brought into con- tact with most of the geological problems that are presented by our earth in a way which, I believe, is afforded nowhere else. The whole country, practically, is bare of soil and the rocks lie ready to the hammer everywhere, while the enor- mous gashes sawn through the land by the rivers reveal sections of unparalleled magnitude and clearness. As year by year went by the facts presented themselves to me in an order different from that stated in the text-books, and the theories as to their origin and nature became simplified and different from established ones. There seemed to me no need to speculate on enigmatical problems, but the facts observed, if allowed to arrange themselves according to their natural sequence, explained many of the problems that are the subject of so much controversy. I feared that in the isolation from centres of current geological thought I had gone off on a side track which led nowhere, but the publica- tion of Professor T. C. Chamberlins Planetismal Hypothesis l showed me that I was travelling in a direction which, at least, was being taken by others. The planetismal hypothesis allows known facts to weigh more than theories, and enables one to build up a system of geology without an appeal to the unknown and unknowable. It is not for me to judge the merits of this hypothesis, but in my opinion most positive advance in natural science that has been made for a very long it is the time. Buf there is more than the planetismal hypothesis there are the logical con- sequences of its acceptance, and as far as I know no comprehensive work has appeared dealing with these, though Professor C. R. van Rises gigantic book on Metamorphism l is a storehouse of facts in favour of the hypothesis. The hypothesis must stand or fall on the merits of the consequences of its acceptance, and I have endeavoured in my own way to set these forth. I have not attempted an exhaustive treatise on the subject-indeed, in this distant corner of the world my means are far too limited to accomplish such a task but I have put together, as far as I have been able to do so, a general statement of the readjustments of our outlook necessitated by this hypothesis. How much of the book owes its matter to the inspiration of the planetismal hypothesis, and how much is my own, I cannot say, but I accept all blame for mistakes in interpretation of the phenomena de- scribed. In many cases I have gone much further than Pro- fessor Chamberlin, but the object I have set before me is to lay the whole case from the single point of view of a solid earth. To look at the subject-matter in a different light I have presented logical deductions from obvious facts, and where they differ from accepted explanations, the fault may lie in my reasoning but as this has been the result of long and sustained association with geological phenomena in the field, some good may accrue from looking at the problems from a new point of view, even if eventually the interpretations are proved to be incorrect. 1 C. R. van Hise, A Treatise on Metamorphism, U.S. Geological Survey Monographs, vol. xlvii. Washington, 1904, pp. 1-1286, 30x23 cm. CONTENTS CHAP... --This text refers to the Paperback edition.