With regard to the subject of Classification, I have in most instances followed that which is adopted by the Geological Survey. But I have introduced some modifications in the classification of the Cambrian, Silurian, and Permian rocks, because they have the sanction of those high in authority, and because in such cases, where even the best of doctors' disagree, I have necessarily had to use my own judgment. In these instances I have not neglected to indicate the opinions thus opposed to each other. Questions of classification are, indeed, of little moment as affecting the truth of geological deductions, and as our knowledge increases, it becomes more and more difficult to define the exact limits of any one period so called, for the history of the earth is but the record of one continued series of more or less gradual changes in scene and in life. It has been considered unnecessary to enter into much detail regarding the geographical distribution of each formation, as this can be best understood by reference to a Geological Map, such as that of Ramsay or Greenough, or the larger Map published in separate sheets by the Geological Survey. The Map accompanying this volume, which has been drawn by Mr. C. L. Griesbach, will be useful as an indexmap, as it displays the geographical extent of the great groups of strata where they are exposed at the surface. I had intended to give the Foreign Equivalents of our strata; but I must confess that I became bewildered with the multiplicity of names, and soon arrived at the conclusion that any effort to do justice to this subject would not only require the constant labour of many years, but would, after all, be somewhat similar to an effort to place in columns the reigns of the several contemporary kings, emperors, and other rulers of different countries, an effort which would entail little else but confusion by reason of the innumerable brackets that such a plan would render necessary. I have therefore strictly confined myself to the geological history of England and Wales. My task has been to gather together all the principal facts, and to arrange them as far as possible in systematic order. Such a record in itself can prove by no means of an entertaining nature. A 'Geology made interesting,' in the popular sense, must necessarily be free from details; but those who seek to understand the principles' will soon make the subject interesting to themselves, especially if they buckle on the hammer and go into the field to study. Not the least difficult portion of my work has been the effort to give due credit to those whose labours are condensed in this volume. I have given a list of the principal publications which I have consulted, but I have refrained from burdening the text with references, believing that not only would this necessitate much repetition, but that in many cases, unless the foot-notes exceeded in bulk the other material, it would be invidious to enumerate the works wherein the facts were originally noticed and discussed. And in many instances it would be well nigh impossible, in a work of so general a nature as the present, to determine to whom we were first indebted for the indication of facts which, after all, would be patent to any observer, and may be regarded as common property. As Edward Forbes observed, the time will come when the author of a view shall be set aside, and the view only taken cognizance of. To many friends and colleagues, however, I am particularly indebted; and firstly I must record very grateful thanks to my Uncle, Mr. Henry Woodward, who has ever been ready to give advice and assistance throughout the progress of the work. To Professor Hughes I am indebted for many corrections and suggestions in the Cambrian and Silurian Chapters, and to Professor Green similarly in regard to the Carboniferous Chapter. Mr. Bristow and Mr. Etheridge kindly examined the Oolitic Chapter; Mr. Topley revised the Lower Cretaceous portions of the book, and Mr. Whitaker those referring to Chalk and Eocene strata. To Professor Rupert Jones I am indebted for sundry remarks upon Chalk-flints; and to Mr. James Geikie for notes on the Glacial Period. I am likewise indebted to Mr. Rutley for several notes in addition to those on the classification of the Igneous and Metamorphic Rocks. Lastly I must record my obligations to Mr. William Longman for the kindly interest he has taken in this work; and both to him and to Mr. C. Puller I must return thanks for many valuable hints and emendations with which they have furnished me while passing the work through the press. The Diagram-sections are either original or from acknowledged sources. The pictorial sections have been prepared by my friend Mr. Edward Fielding, some from photographs, others from very rough drawings furnished by myself; and all the woodcuts have been engraved by Mr. G. Shayler. While I acknowledge the kind assistance of friends, I must add that they are by no means responsible for any errors or omissions that may be found in the chapters they have looked over, nor for any of the opinions given, except where expressly stated. Notices of all errors and omissions will be gratefully received, with, it is hoped, a full pardon for such transgressions. 8th July, 1876. HORACE B. WOODWARD. |