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PRINCIPLES OF GEOLOGY -- VOLUME 3 |
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View of the Volcanoes around Olot in Catalonia PRINCIPLES OF GEOLOGY, BEING AN ATTEMPT TO EXPLAIN THE FORMER CHANGES OF THE EARTH'S SURFACE, BY REFERENCE TO CAUSES NOW IN OPERATION. BY
CHARLES LYELL, ESQ., F.R.S., IN THREE VOLUMES. VOL. III. LONDON:
JOHN MURRAY, ALBEMARLE-STREET. LONDON: TO
RODERICK IMPEY MURCHISON, ESQ., F.R.S., My DEAR MURCHISON, I HAVE great pleasure in dedicating this volume to you, as it contains the results of some of our joint labours in the field, in Auvergne, Velay, and Piedmont -- results which had not yet been communicated to the public through any other channel. When we quitted England together for a tour on the continent. in May, 1828, the first sketch only of my 'Principles of Geology' was finished. Since that time you have watched the progress of the work with friendly interest, and, as President of the Geological Society, have twice expressed in your Anniversary Addresses, your participation in many of my views, which were warmly controverted by others. The eulogy which you have lately pronounced from the chair, on the last part of my work, (whether I attribute your approval to the exercise of an unbiassed judgment or to the partiality of a friend,) could not fail to be most gratifying to my feelings, and I trust that you will long enjoy health and energy to continue to promote with enthusiasm the advancement of your favourite science. Believe me, my dear Murchison, Yours, &c. &c. CHARLES LYELL. PREFACE THE original MS. of the 'Principles of Geology' was delivered to the publisher at the close of the year 1827, when it was proposed that it should appear in the course of the year following, in two volumes octavo. Since that time many causes have concurred to delay the completion of the work, and, in some degree, to modify the original plan. In May, 1828, when the preliminary chapters on the History of Geology, and some others which follow them in the first volume, were nearly finished, I became anxious to visit several parts of the continent, in order to acquire more information concerning the tertiary formations. Accordingly, I set out in May, 1828, in company with Mr. Murchison, on a tour through France and the north of Italy, where we examined together many districts which are particularly mentioned in the body of this work. We visited Auvergne, Velay, Cantal, and the Vivarais, and afterwards the environs of Aix, in Provence, and then passed by the Maritime Alps to Savona, thence crossing to Piedmont by the Valley of the Bormida. At Turin we found Signor Bonelli engaged in the arrangement of a large collection of tertiary shells obtained chiefly from the Italian strata; and as I had already conceived the idea of classing the different tertiary groups, by reference to the proportional number of recent species found fossil in each, I was at pains to learn what number Signor Bonelli had identified with living species, and the degree of precision with which such identifications could be made. With a view of illustrating this point, he showed us suites of shells common to the Subapennine beds and to the Mediterranean, pointing out that in some instances not only the ordinary type of the species, but even the different varieties had their counterparts both in the fossil and recent series. The same naturalist informed us that the fossil shells of the hill of the Superga, at Turin, differed as a group from those of Parma and other localities of the Subapennine beds of northern Italy; and, on the other hand, that the characteristic shells of the Superga agreed with the species found at Bordeaux and other parts of the South of France. I was the more struck with this remark, as Mr. Murchison and myself had already inferred that the highly-inclined strata of the Valley of the Bormida, which agree with those of the Superga, were older than the more horizontal Subapennine marls, by which the plains of the Tanaro and the Po are skirted. When we had explored some parts of the Vicentin together, Mr. Murchison re-crossed the Alps, while I directed my course to the south of Italy, first staying at Parma, where I studied, in the cabinets of Signor Guidotti, a beautiful collection of Italian tertiary shells, consisting of more than 1000 species, many of which had been identified with living testacea. Signor Guidotti had not examined his fossils with reference to their bearing on geological questions, but computed, on a loose estimate, that there were about 30 per cent. of living species in the Subapennine beds. I then visited Florence, Sienna, and Rome, and the results of my inquiries respecting the tertiary strata of those territories will be found partly in the body of the work, and partly in the catalogues given in Appendix II. On my arrival at Naples I became acquainted with Signor O. G. Costa, who had examined the fossil shells of Otranto and Calabria, and had collected many recent testacea from the seas surrounding the Calabrian coasts. His comparison of the fossil and living species had led him to a very different result in regard to the southern extremity of Italy, from that to which Signors Guidotti and Bonelli had arrived in regard to the north, for he was of opinion that few of the tertiary shells were of extinct species. In confirmation of this view, he showed me a suite of fossil shells from the territory of Otranto, in which nearly all the species were recent. In October, 1828, I examined Ischia, and obtained from the strata of that island the fossil shells named in Appendix II., p. 57. They were all, with two or three exceptions, recognized by Signor Costa as species now inhabiting the Mediterranean, a circumstance which greatly astonished me, as I procured some of them at the height of 2000 feet above the level of the sea (Vol. iii. p. 126). Early in November, 1828, I crossed from Naples to Messina, and immediately afterwards examined Etna, and collected on the flanks of that mountain, near Trezza, the fossil shells alluded to in the third volume (p. 79, and Appendix II., p. 53). The occurrence of shells in this locality was not unknown to the naturalists of Catania, but having been recognized by them as recent species, they were supposed to have been carried up from the sea-shore to fertilize the soil, and therefore disregarded. Their position is well known to many of the peasants of the country, by whom the fossils are called 'roba di diluvio.' In the course of my tour I had been frequently led to reflect on the precept of Descartes, C that a philosopher should once in his life doubt every thing he had been taught;' but I still retained so much faith in my early geological creed as to feel the most lively surprise, on visiting Sortino, Pentalica, Syracuse, and other parts of the Val di Noto, at beholding a limestone of enormous thickness filled with recent shells, or sometimes with the mere casts of shells, resting on marl in which shells of Mediterranean species were imbedded in a high state of preservation. All idea of attaching a high antiquity to a regularly stratified limestone, in which the casts and impressions of shells alone were discernible, vanished at once from my mind. At the same time, I was struck with the identity of the associated igneous rocks of the Val di Noto with well known varieties of 'trap' in Scotland and other parts of Europe, varieties, which I had also seen entering largely into the structure of Etna. I occasionally amused myself with speculating on the different rate of progress which Geology might have made, had it been first cultivated with success at Catania, where the phenomena above alluded to, and the great elevation of the modern tertiary beds in the Val di Noto, and the changes produced in the historical era by the Calabrian earthquakes, would have been familiarly known. From Cape Passaro I passed on by Spaccaforno and Licata to Girgenti, where I abandoned my design of exploring the western part of Sicily, that I might return again to the Val di Noto and the neighbourhood of Etna, and verify the discoveries which I had made. With this view I travelled by Caltanisetta, Piazza, Caltagirone, Vizzini, Militello, Palagonia, Lago Naftia, and Radusa, to Castrogiovanni, and from thence to Palermo, at which last place I procured the shells named in Appendix II. p. 55. The sections on this new route confirmed me in my first opinions respecting the Val di Noto, as will appear by the 6th, 8th, and 9th chapters of the third Volume. When I again reached Naples, in January, 1829, I found that Signor O. G. Costa had examined the ter tiary fossils which I had sent to him from different parts of Sicily, and declared them to be for the most part of recent species. I then bent my course homeward, seeing at Genoa, Professor Viviani and Dr. Sasso, the last of whom put into my hands his memoirs on the strata of Albenga (see vol. iii. p. 166) in which I found, that, according to his list of shells, the tertiary formations at the foot of the maritime Alps contained about 50 per cent. of recent species. I next re-visited Turin, and communicated to Signor Bonelli the result of my inquiries respecting the tertiary beds of the south of Italy, and of Sicily, upon which he kindly offered to review his fossils, some of which had been obtained from those countries, and to compare them with the Subapennine shells of northern Italy. He also promised to draw up immediately a list of the shells characteristic of the green-sand of the Superga, and common to that locality and Bordeaux, that I might publish it at the end of my second volume; but the death of this amiable and zealous naturalist soon afterwards deprived me of the benefit of his assistance. I had now fully decided on attempting to establish four sub-divisions of the great tertiary epoch, the same which are fully illustrated in the present work. I considered the basin of Paris and London to be the type of the first division; the beds of the Superga, of the second; the Subapennine strata of northern Italy, of the third; and Ischia and the Val di Noto, of the fourth. I was also convinced that I had seen proofs, during my tour in Auvergne, Tuscany and Sicily, of volcanic rocks contemporaneous with the sedimentary strata of three of the above periods. On my return to Paris, in February, 1829, I communicated to M. Desnoyers some of the new views to which my examination of Sicily had led me, and my intention to attempt a classification of the different tertiary formations in chronological order, by reference to the comparative proportion of living species of shells found fossil in each. He informed me, that during my tour he had been employed in printing the first part of his memoir, not yet published, 'on the Tertiary Formations more recent than the Paris basin,' in which he had insisted on the doctrine 'of the succession of tertiary formations of different ages.' At the end of the first part of his memoir, which was published before I left Paris, [1] he annexed a note on the accordance of many of my views with his own, and my intention of arranging' the tertiary formations chronologically, according to the relative number of fossils in each group, which were identifiable with species now living. At the same time I learned from M. Desnoyers, that M. Deshayes had, by the mere inspection of the fossil shells in his extensive museum, convinced himself that the different tertiary formations might be arranged in a chronological series. I accordingly lost no time in seeing M. Deshayes, who explained to me the data on which he considered that the three ter tiary periods mentioned in the Tables, Appendix I., might be established. I at once perceived that the fossils obtained by me in my tour would form but an inconsiderable contribution to so great a body of zoological evidence as M. Deshayes had already in his possession. I therefore requested him to examine my shells when they arrived from Italy, and expressed my great desire to obtain his co-operation in my work, in which, as will appear in the sequel, I was fortunate enough to succeed. The preparation of my first volume had now been suspended for nine months, and was not resumed until my return to London in the beginning of March, 1829. Before the whole was printed another summer arrived, and I again took the field to examine 'the Crag,' on the coasts of Essex, Norfolk, and Suffolk. The first volume appeared at length in January, 1830, after which I applied myself to perfect what I had written on 'the changes in the organic world,' a subject which merely occupied four or five chapters in my original sketch, but which was now expanded into a small treatise. Before this part was completed another summer overtook me, and I then set out on a geological expedition to the south of France, the Pyrenees, and Catalonia. On my return to Paris, in September, 1830, I studied for six weeks in the museum of M. Deshayes, examining his collection of fossil and recent shells, and profiting by his instructions in conchology. As he had not yet published any of the general results deducible from his valuable collection, I requested him to furnish me with lists of those species of shells which were common to two or more tertiary periods, as also the names of those known to occur both in some tertiary strata and in a living state. This he engaged to do, and we agreed that the information should be communicated in a tabular form. After several modifications of the plan first proposed for the Tables, we finally agreed upon the manner in which they should be constructed, and the execution was left entirely in the hands of M. Deshayes, in whose name they were to appear in my second volume. The tables were sent to me in the course of the following spring (1831), and additions and corrections several months later. They contained not only the information which I had expected, but much more, for the names of several hundred species were added, as being common to two or more formations of the same period, whereas it was originally proposed to insert those only which were known to be common to two or more distinct periods. Thus, for example, more than 50 shells are now included in the tables, on the ground that they are common to the tertiary strata both of the London and Paris basins, although they only occur in the Eocene period to which the strata of those basins belong. The names thus added will increase the value of the tables, and give a more complete view of the point to which fossil conchology has now reached; at the same time, it must be admitted that tables of shells cannot be perfected on this plan, as the science advances from year to year, without soon outgrowing the space which could reasonably be allotted to fossil conchology in a work on geology, for they would soon embrace the names of the greater number of known shells, nearly all of these being common to different groups of strata of the same period. Some of the catalogues which I have given in Appendix II., of fossil shells from the neighbourhood of the Red Sea, and from some other localities, may illustrate this remark, as they lead us to anticipate that, at no distant time, we may find a large proportion of all the Recent species in a fossil state. In treatises on fossil conchology, such as I trust M. Deshayes will soon publish, we cannot have too complete a catalogue of all the species which have been found fossil in every locality, together with their synonyms; but in geological works we can only illustrate the more important theoretical points by catalogues of those shells which are either characteristic of particular periods, as being exclusively confined to them, or which show the connexion of two periods, by being common to each. For this purpose we must select certain normal groups which do not approximate too closely to each other, and enumerate by name the species common to more than one of these. Thus, for example, we might omit in our tables the Newer Pliocene formations altogether, and enumerate the shells common to the Recent and Older Pliocene beds. I have arranged the tertiary formations in four groups, as I had determined to do before I was acquainted with M. Deshayes; and in his tables he has referred the shells to three periods, according to which he had classed them before he had any communication with me. No confusion, however, will arise from this want of conformity between the tables and my classification, since I have named two of my periods (the Newer and Older Pliocene) as subdivisions of one of his; and by reference to the Synoptical Table, at p. 61, the reader will see which localities mentioned in M. Deshayes's Tables belong to the Newer and which to the Older Pliocene period. In the summer of 1831 I made a geological excursion to the volcanic district of the Eifel, and on my return I determined to extend my work to three volumes, the second of which appeared in January, 1832. The last volume has been delayed till now by many interruptions, among which I may mention a tour, in the summer of 1832, up the valley of the Rhine, when I examined the loess (vol. iii. p. 151), and a visit, on my way home through Switzerland, to the Valorsine, where I had an opportunity of verifying the observations of M. Necker on the granite veins and altered stratified rocks of that district. I may also mention the time occupied in the correction of the second edition of the first and second volumes, and the delivery of a course of Lectures in May and June, 1832, at King's College, London, on which occasion I had an opportunity of communicating to the scientific world a great part of the views now explained in my last volume. London, April, 1833. TABLE OF CONTENTS:
Table I. Showing the relations of the various classes of rocks, the Alluvial, the Aqueous, the Volcanic, and the Hypogene, of different periods Table II. Showing the order of superposition of the principal European groups of sedimentary strata mentioned in this work Notes in explanation of the Tables of fossil shells in Appendix I. Appendix I. Tables of fossil shells by Monsieur G. P. Deshayes Appendix II. Lists of fossil Shells chiefly collected by the author in Sicily and Italy, named by M. Deshayes Glossary, containing an explanation of geological and other scientific terms used in this work Index LIST OF PLATES AND WOOD-CUTS IN THE THIRD VOLUME. PLATES. Frontispiece. View of the volcanos around Olot, in Catalonia. See p. 186. This view is taken from a sketch by the author; an attempt is made to represent by colours the different geological formations of which the country is composed. The blue line of mountains in the distance are the Pyrenees, which are to the north of the spectator, and consist of primary and ancient secondary rocks. In front of these arc the secondary formations~ described in chap. xiv., coloured purplish-grey of different tints, to express different distances. The flank of the hill, in the foreground, called Costa di Pujou, is composed partly of secondary rocks, which are seen to the left of a small bridle- road, and partly of volcanic, the red colour expressing lava and scoriae. Several very perfect volcanic cones, chiefly composed of red scoriae, and having craters on their summits, are seen in the immediate neighbourhood of Olot, coloured red. The level plain on which that town stands has clearly been produced by the flowing down of many lava-streams from those hills into the bottom of a valley, probably once of considerable depth, like those of the surrounding country, but which has been in a great measure filled up by lava. The reader should be informed, that in many impressions of this plate Montsacopa is mis-spelt 'Montescopa,' and Mount Garrinada is mis-spelt 'Gradenada.' Plate 1. The shells represented in this plate have been selected by M. Deshayes as characteristic of the Pliocene period of the Tables, Appendix I. The greater part of them are common both to the older and newer Pliocene periods of this work. Eight of the species, Nos. 1, 3, 5, 6, 7, 9, 13, and 14, are now living, but are given as being also found in the Older Pliocene formations. Fusus crispus is not found either recent or in the Miocene or Eocene formations, but occurs both in the Newer and Older Pliocene strata. Mitra plicatula has been found only in the older Pliocene deposits. The Turbo rugosus was considered as exclusively Pliocene when selected by M. Deshayes, but M. Boue has since found it in the Miocene strata at Vienna and Moravia (see Tables, Appendix I. p. 26). Buccinum semistriatum is also a Miocene shell, but was inserted as being peculiarly abundant in the Pliocene strata. Plate II. All the shells figured in this plate, except Cardita Ajar, are very characteristic of the Miocene formations; that is to say, they are found in that period and no other. Cardita Ajar is also very common in the Miocene strata, but is also a Recent species. It has not yet been observed in any Pliocene deposit. Plate III. The species of shells figured in this plate are characteristic of the Eocene period, as being exclusively confined to deposits of that period, and for the most part abundant in them. Plate IV. The microscopic shells of the order Cephalopoda, figured in this plate, are characteristic of the Eocene period, and are distinct from the microscopic shells of the Older Pliocene formations of Italy. The figures are from unpublished drawings by M. Deshayes, who has selected some of the most remarkable types of form. The reader will observe, that the minute points, figures 4, 8, 11, 14, and 18, indicate the natural size of the species which are represented. (For observations on these shells see p. 251.) Plate V. Geological Map of the south-east of England, exhibiting the Denudation of the Weald. This map has been compiled in great part from Mr. Greenough's Geological Map of England, and Mr. Mantell's Map of the south-east of England. (Illustrations of Geol. of Sussex, and fossils of Tilgate Forest, 1827.) The eastern extremity of the 'denudation' is reduced from Mr. Murchison's Map of that district. (Geol. Trans., 2nd series, vol. ii. part i. plate 14.) The object of this map is fully explained in chapters xxi. and xxii. of this volume. LIST OF WOOD-CUTS. 1. Diagram showing the order of succession of stratified masses 2. Diagram showing the relative position of the Primary, Secondary, and Tertiary strata 3. Diagram showing the relative age of the strata of the Paris basin, and those of the basin of the Loire, in Touraine 4. Diagram showing the same in the strata of Suffolk and Piedmont 5. Diagram containing sections in the Val di Noto, Sicily 6 & 7. Horizontal sections of dikes near Palagonia 8. Section of horizontal limestone in contact with inclined strata of Tuff in the hill of Novera, near Vizzini 9. Section of calcareous grit and peperino, east of Palagonia, south side of the pass 10. Section of the same beds on the north side of the pass 11. Outline view of the cone of Etna from the summit of the limestone platform of Primosole 12. Section from Paterno by Lago di Naftia to Palagonia 13. Section of beds of clay and sand capped by columnar basalt and conglomerate at La Motta, near Catania 14. View of the Isle of Cyclops, in the Bay of Trezza 15. Diagram showing the contortions in the newer Pliocene strata of the Isle of Cyclops 16. Horizontal section showing the invasion of the newer Pliocene strata of the Isle of Cyclops by lava 17. Wood-cut showing the great valley on the east side or Etna 18. Diagram explanatory of the origin of the Valleys of Calanna and St. Giacomo, on Etna 19. View of dikes at the base of the Serre del Solfizio, Etna 20. View of tortuous dikes or veins of lava, Punto di Guimento, Etna 21. View of the rocks Finochio, Capra, and Musara, in the Val del Bove 22. View from the summit of Etna into the Val del Bove 23. View of the Valley called Gozzo degli Martiri, below Melilli 24. Diagram showing the manner of obliteration of successive lines of sea-cliff 25. View of dikes or veins of lava at the Punto del Nasone, on Somma 26. Diagram showing the superposition of alluvium and cave deposits containing extinct quadrupeds to a limestone containing recent shells 27. Diagram showing the position of the Cave of San Ciro, near Palermo 28. Diagram showing the position of Tertiary strata at Genoa 29. Section from Monte Calvo to the sea by the Valley of Magnan, near Nice 30. Diagram showing the manner in which the Crag may be supposed to rest on the chalk 31. Section of shelly crag near Walton, Suffolk 32. Section at the light-house near Happisborough 33. Section of Little Cat Cliff, showing the inclination of the layers of quartzose sand in opposite directions 34. Lamination of shelly sand and loam, near the Signal-House, Walton 35. Diagram illustrative of the successive deposition of strata 36. Section of ripple marks caused by the wind on loose sand 37. Bent strata of loam in the cliffs between Cromer and Runton 38. Folding of the strata between East and West Runton 39. Section in the cliffs east of Sherringham 40. Section east of Sherringham, Norfolk 41. Side view of a promontory of chalk and crag, at Trimmingham, Norfolk 42. Northern protuberance of chalk, Trimmingham 43. Map of the volcanic district of Catalonia 44. Section of volcanic sand and ashes in a valley near Olot 45. Section above the bridge of Cellent 46. Section at Castell Follit 47. Superposition of rocks in the volcanic district of Catalonia 48. Map of the volcanic district of the Lower Rhine 49. View of the Gemunden Maar 50. Section of the same and other contiguous lake-craters 51. Section of tertiary strata overlying chalk near Dax 52. Section explaining the position of the Eocene strata in the Bordeaux basin 53. Section of Inland cliff near Dax 54. Position of the Miocene alluviums of Mont Perrier (or Boulade) 55. Section of the fresh-water formation of Cadibona 56. Map of Auvergne, Cantal, Velay, &c. 57. Section of Vertical marls near Clermont 58 & 59. Superposition of the formations of the Paris basin 60. Section of the Hill of Gergovia near Clermont 61. Lavas of Auvergue resting on alluviums of different ages 62. Map of the principal tertiary basins of the Eocene period 63. Section from the London to the Hampshire basin across the Valley of the Weald 64. Section of the country from the confines of the basin of London to that of Hants, with the principal heights above the level of the sea on a true scale 65. View of the chalk escarpment of the South Downs, taken from the Devil's Dike, looking towards the west and south-west 66. Chalk escarpment as seen from the hill above Steyning, Sussex. The castle and village of Bramber in the foreground 67. Section of lower terrace of firestone 68. Diagram explanatory of anticlinal and synclinal lines 69 & 70. Sections illustrating the gradual denudation of the Weald Valley 71. Section from the north escarpment of the South Downs to Barcombe 72. Section of cliffs west of Sherringham 73. View of the transverse valley of the Adur in the South Downs 74. Supposed section of a transverse valley 75. View of Lewes Coomb 76. Section of a fault in the cliff-hills near Lewes 77. Hypothetical section to illustrate the question of the denudation of the Weald Valley 304 78. Ground plan of the Valley of Kingsclere 79. Section across the Valley of Kingsclere from north to south 80. Section of the Valley of Kingsclere with the heights on a true scale 81. Hypothetical section illustrating the denudation of the Weald Valley and the contemporaneous origin of the Eocene strata 82 & 83. Diagrams illustrative of the relative antiquity of mountain-chains 84. Diagram showing the relative position of the Hypogene sedimentary and volcanic rocks 85. Granite veins traversing stratified rocks 86. Granite veins traversing gneiss at Cape Wrath in Scotland 87. Granite veins passing through hornblende slate, Carnsilver Cove, Cornwall 88. View of the junction of granite and limestone in Glen Tilt 89. Lamination of clay-slate, Montagne de Seguinat, near Gavarnie, in the Pyrenees 90. Junction of granite with jurassic or oolite strata in the Alps 91. Diagram showing the different order of position in the Plutonic and Sedimentary formations of different ages 92. Diagram to explain the meaning of the term 'fault,' Glossary 93. Diagram to explain the term' salient angle,' Glossary ERRATA. Page 89, line 11 from the top, for vivid, read livid.
Plate 1. The shells represented in this plate have been selected by M. Deshayes as characteristic of the Pliocene period of the Tables, Appendix I. The greater part of them are common both to the older and newer Pliocene periods of this work. Eight of the species, Nos. 1, 3, 5, 6, 7, 9, 13, and 14, are now living, but are given as being also found in the Older Pliocene formations. Fusus crispus is not found either recent or in the Miocene or Eocene formations, but occurs both in the Newer and Older Pliocene strata. Mitra plicatula has been found only in the older Pliocene deposits. The Turbo rugosus was considered as exclusively Pliocene when selected by M. Deshayes, but M. Boue has since found it in the Miocene strata at Vienna and Moravia (see Tables, Appendix I. p. 26). Buccinum semistriatum is also a Miocene shell, but was inserted as being peculiarly abundant in the Pliocene strata.
Plate II. All the shells figured in this plate, except Cardita Ajar, are very characteristic of the Miocene formations; that is to say, they are found in that period and no other. Cardita Ajar is also very common in the Miocene strata, but is also a Recent species. It has not yet been observed in any Pliocene deposit.
Plate III. The species of shells figured in this plate are characteristic of the Eocene period, as being exclusively confined to deposits of that period, and for the most part abundant in them.
Plate IV. The microscopic shells of the order Cephalopoda, figured in this plate, are characteristic of the Eocene period, and are distinct from the microscopic shells of the Older Pliocene formations of Italy. The figures are from unpublished drawings by M. Deshayes, who has selected some of the most remarkable types of form. The reader will observe, that the minute points, figures 4, 8, 11, 14, and 18, indicate the natural size of the species which are represented. (For observations on these shells see p. 251.)
[In the original publication, Plate V was hand painted in six colors. We have adapted the colors to shading in order to print the map in black and white.] Plate V. Geological Map of the south-east of England, exhibiting the Denudation of the Weald. This map has been compiled in great part from Mr. Greenough's Geological Map of England, and Mr. Mantell's Map of the south-east of England. (Illustrations of Geol. of Sussex, and fossils of Tilgate Forest, 1827.) The eastern extremity of the 'denudation' is reduced from Mr. Murchison's Map of that district. (Geol. Trans., 2nd series, vol. ii. part i. plate 14.) The object of this map is fully explained in chapters xxi. and xxii. of this volume. _______________ Notes: 1. Ann. des Sci. Nat., tome xvi. p. 214. |
