THE BUILDING OF THE BRITISH ISLES: A STUDY IN GEOGRAPHICAL EVOLUTION. BY A. J. JUKES-BROWNE, B. A., F. G. S., OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES; Illustrated by Maps and Woodcuts. SECOND EDITION, REVISED. LONDON: GEORGE BELL & SONS, YORK ST., COVENT GARDEN, AND NEW YORK. 1892. (141411 Vidi ego quod fuerat quondam solidissima tellus Esse fretum. Vidi factas ex æquore terras. OVID, Metam. xv. 262. The hills are shadows and they flow From form to form, and nothing stands; They melt like mist, the solid lands, Like clouds they shape themselves and go. TENNYSON, In Memoriam. 50 G THE PREFA CЕ. `HE domain of Geological Science has many pathways, and these paths lead toward many different goals. The complete geological investigation of a country is the work of many heads and hands; many individual workers must survey the ground, note the exposures, and collect the fossils, before any of these pathways can be followed to its ultimate issue, or any complete history can be constructed out of the torn and scattered pages of the geological record. From this record several distinct histories may be transcribed. The biologist may restore the successive faunas and floras which have occupied the region; the petrologist may describe the various kinds of rocks, both aqueous and igneous, which have been formed during each successive period of time; the physical geologist may expound the conditions under which these rocks have been formed, or may endeavour to restore the geographical outlines of the seas and lakes in which they have been accumulated; the physical geographer may explain the gradual development of the present physical features of the country. The aim of this volume is the restoration of the physical and geographical conditions which prevailed in the British area during each of the great periods of time which make up our geological sequence. The pioneer in this branch of geological science was Mr. Godwin-Austen, whose masterly essays published in the "Quarterly Journal of the Geological Society," between 1856 and 1866, may still be read with advantage, for many of his conclusions have been confirmed by the information subsequently derived from deep borings in the eastern and midland counties. Many geologists have dealt in more or less detail with the geographical conditions of particular epochs, but the first systematic treatise on the geography of successive geological periods was that by Professor Hull, published in 1882, and entitled, "Contributions to the Physical History of the British Isles." The larger part of Professor Hull's book, however, is devoted to the consideration of the Paleozoic periods and the origin of the Atlantic Ocean; the space allotted to the Neozoic periods being hardly proportionate to the knowledge that we really possess concerning them. The aim and scope of the present volume are somewhat different from Professor Hull's, the successive periods of Neozoic time being treated at much greater length than those of Paleozoic time, partly because much more information is available, but chiefly because it is my object to trace out the succession of physical and geographical changes which have led up to the existing disposition of land and water in the north-western portion of Europe. The restoration of the geography of any past period is a problem of great difficulty, and the more remote that period is from the present time the greater does this difficulty become. In the first edition of this book I felt that the available evidence was really insufficient to warrant very definite restorations of any of the Paleozoic periods except the Carboniferous and the Permian. In preparing this edition I have availed myself of the many recent discoveries among the Paleozoic and Archæan rocks, and have thus been able to improve upon my former attempts; but we |