Name: The Medals of Creation, Volumes 1 and 2 First Lessons in Geology and the Study of Organic Remains
Author: Gideon Algernon Mantell

Opening

Transcriber Note

To preserve cross-references between the volumes, both have been combined into one. Text emphasis denoted by Italics. Whole and fractional parts of numbers displayed as 123-4/5.

THE

Medals of Creation;

OR,

FIRST LESSONS IN GEOLOGY,

AND

THE STUDY OF ORGANIC REMAINS.

VOL. I.

"If we look with wonder upon the great remains of human works, such as the columns of Palmyra, broken in the midst of the desert; the temples of Pæstum, beautiful in the decay of twenty centuries; or the mutilated fragments of Greek sculpture in the Acropolis of Athens, or in our own museums, as proofs of the genius of artists, and power and riches of nations now past away; with how much deeper feeling of admiration must we consider those grand monuments of nature which mark the revolutions of the Globe; continents broken into islands; one land produced, another destroyed; the bottom of the ocean become a fertile soil; whole races of animals extinct, and the bones and exuviæ of one class covered with the remains of another; and upon the graves of past generations--the marble or rocky tombs, as it were, of a former animated world--new generations rising, and order and harmony established, and a system of life and beauty produced out of chaos and death; proving the infinite power, wisdom, and goodness of the Great Cause of all things!"--Sir H. Davy.

THE

Medals of Creation;

OR,

FIRST LESSONS IN GEOLOGY,

AND

THE STUDY OF ORGANIC REMAINS.

GIDEON ALGERNON MANTELL, LL.D. F.R.S. V.P.G.S.

PRESIDENT OF THE WEST LONDON MEDICAL SOCIETY, ETC. AUTHOR OF THE WONDERS OF GEOLOGY, ETC.

"Voilà! une nouvelle espèce de médailles, beaucoup plus importantes, et incomparablement plus anciennes, que toutes celles des Grecs et des Remains!"--Knorr, Monumens des Catastrophes.

IN TWO VOLS.--VOL. 1.

CONTAINING

Fossil Vegetables, Zoophytes, Echinoderms, and Molluscs.

SECOND EDITION, ENTIRELY REWRITTEN.

LONDON:

HENRY G. BOHN, YORK STREET, COVENT GARDEN.

MDCCCLIV

LONDON:

R. CLAY, PRINTER, BREAD STREET HILL.

MY SONS,

WALTER MANTELL,

OF WELLINGTON, NEW ZEALAND,

AND

REGINALD NEVILLE MANTELL,

OF KENTUCKY, UNITED STATES,

This Work

MY LAST ATTEMPT TO PROMOTE THE ADVANCEMENT

OF SCIENTIFIC KNOWLEDGE,

IS MOST AFFECTIONATELY INSCRIBED.

G. A. M.

Chester Square, Pimlico, Feb. 3, 1853.

[The above having been penned by the much-lamented author of the "Medals" some months previous to his decease, it is retained in this posthumous edition of his favourite work as an appropriate dedication, dictated by the parental affection of one of the chief promoters of geological science in England, and addressed to his absent sons, whose works have already shown them to be enthusiastic labourers in the same field, both at home and in distant parts of the world.]

PREFATORY NOTE TO THE SECOND EDITION.

The untimely Decease of the lamented Author of the "Medals of Creation" during the progress of the present edition through the press has unavoidably delayed its publication.

The First Volume has been wholly rewritten by the Author.

The materials of the Second Volume had been elaborately revised and much enlarged by Dr. Mantell previously to his Decease. The Editor has laboured to carry out the intentions of the Author in rendering this part of the Work as complete a compendium as possible of the Palæontological history of the Organic Beings of which it treats, and in adapting it to the requirements of the Geological Student of the present time.

The various sources from which palæontological and zoological information has been derived have, for the most part, been adverted to in the text or in the footnotes. The Editor, however, has especially to acknowledge the kindness of Mr. J. Morris, F.G.S., in allowing him to refer to the proof-sheets of the forth-coming edition of his "Catalogue of British Fossils," and thereby affording him important assistance in making correct statements of the distribution of the Fossil Remains of the Crustacea, Insecta, and Vertebrata, in the strata of the British Islands.

T. Rupert Jones.

PREFACE TO THE FIRST EDITION.

In the first edition of the Wonders of Geology, an intention was expressed of immediately publishing, as a sequel to those volumes, "First Lessons," or an Introduction to the Study of Petrifactions, for persons wholly unacquainted with the nature of Fossil Remains; but the completion of the contemplated work was unavoidably postponed, from year to year, by the long and severe indisposition of the Author.

In the meanwhile several works professing the same object have issued from the press; and an enlarged edition of Sir C. Lyell's "Elements" has also appeared, in which the elementary principles of physical Geology are fully illustrated, and numerous figures given of the characteristic fossils of the several formations, or groups of strata. But that department of the science which especially treats of Organic Remains is necessarily considered in a cursory manner; and a work upon the plan originally contemplated by the Author seems still to be required, to initiate the young and uninstructed in the study of those Medals of Creation--those electrotypes of nature--the mineralized remains of the plants and animals which successively flourished in the earlier ages of our planet, in periods incalculably remote, and long antecedent to all human history and tradition.

With this conviction the present volumes are offered, with such modifications of the original plan as circumstances have rendered necessary, as a guide for the Student and the Amateur Collector of fossil remains; for the intelligent Observer who may desire to possess a general knowledge of the subject, without intending to pursue Geology as a science; and for the Tourist who may wish, in the course of his travels, to employ profitably a leisure hour in quest of those interesting memorials of the ancient physical revolutions of our globe, which he will find everywhere presented to his observation.

Crescent Lodge, Clapham Common, May, 1844.

ADDRESS TO THE READER.

"Some books are to be tasted--others to be swallowed--and some few to be chewed and digested; that is, some Books are to be read only in parts--others to be read, but not curiously--and some few to be read wholly and with diligence and attention."--Lord Bacon's Essays.

Anxious that the "Courteous Reader" should derive from this work all the information it is designed to impart, the Author presumes to offer a few words in explanation of the plan upon which it has been constructed, and some suggestions as to the best means of rendering its contents most available to the varied tastes and pursuits of different classes of readers.

In its arrangement, a three-fold object was had in view; namely, in the first place, to present such an epitome of Palæontology, the science which treats of the fossil remains of the ancient inhabitants of the Globe, as shall enable the intelligent Observer to comprehend the nature of the principal discoveries in modern Geology, and the method of investigation by which such highly interesting, and unexpected results, have been obtained..

Secondly, to assist the Collector in his search for Organic Remains,--directing attention to those objects which possess the highest interest, and are especially deserving of accurate examination--instructing him in the art of developing and preserving the specimens he may discover--and pointing out the means to be pursued, for ascertaining their nature, and their relation to existing plants or animals.

Thirdly, to place before the Student a familiar exposition of the elementary principles of Palæontology, based upon a general knowledge of the structure of vegetable and animal organization; to excite in his mind a desire for further information, and prepare him for the perusal and study of works of a higher order than these unpretending volumes; and to point out the sources from which the required instruction may be derived.

Although fully aware of the imperfect manner in which these intentions are fulfilled, the Author hopes that the indulgence claimed by one of the most able writers of our times may be extended to him; and that, "if the design be good upon the whole, the work will not be censured too severely for those faults, from which, in parts, its very nature would scarcely allow it to be free."[1]

[1] Sir E. B. Lytton--preface to the second edition of "The Disowned."

With regard to the best means of making use of these volumes, the advice of the great founder of Inductive Philosophy, on the Study of Books in general, expressed in the quotation prefixed to this address, is peculiarly applicable to the different classes of readers for whom the work is designed.

Thus, "the Book may be tasted, that is, read only in parts," by the intelligent reader, who requires but a general acquaintance with the subjects it embraces. The perusal of the introductory and concluding remarks of each chapter, of the general descriptions of fossil remains, and of the circumstances under which they occur,--omitting the scientific terms and descriptions,--and a cursory examination of the illustrations, will probably satisfy his curiosity; and the work may be transferred to the library for occasional reference, or taken as a travelling companion and guide to some interesting geological district.

But the Book "must be swallowed, that is, read, but not curiously," by the reader desirous of forming a collection of organic remains. A general acquaintance with its contents, and a careful investigation of the characters of the fossils, and comparison with the figures and descriptions, will be requisite to enable the amateur collector to determine the nature of the specimens he may discover.

By the Student the Book "must be digested, that is, read wholly, and with diligence and attention." He should fully comprehend one subject before he advances to the consideration of another, and should test the solidity of his knowledge by practical research. He should visit some of the localities described; collect specimens, and develope them with his own hands; examine their structure microscopically; nor rest satisfied until he has determined their general characters, and ascertained their generic and specific relations. Nor is this an arduous or irksome task; by a moderate degree of attention, a mind of average ability may quickly overcome the apparent difficulties, and will find in the knowledge thus acquired, and in the accession of mental vigour which such investigations never fail to impart, an ample reward for any expenditure of time and trouble.

It is, indeed, within the power of every intelligent reader, by assiduity and perseverance, to attain the high privilege of those who walk in the midst of wonders, in circumstances where the uninformed and uninquiring eye can perceive neither novelty nor beauty; and of being

"Even as one, Who by some secret gift of soul or eye, In every spot beneath the smiling sun. Sees where the Springs of living Waters lie!"

VOL. I.

Dedication, p. v.

Prefatory Note to the Second Edition, vii.

Preface to the First Edition, ix.

Address to the Reader, xi.

Table of Contents, xv.

Description of the Plates, xix.

List of Lignographs in Vol. I., xxxi.

Introduction, 1.

Preliminary Remarks:--On the Plan of the Work and the Arrangement and Subdivision of the subjects it embraces, 8. Works of Reference, 8. Explanation of Terms, 11. List of subjects, 12.

I. On the Nature and Arrangement of the British Strata and their Fossils, 15

Chapter II.--Synopsis of the British Strata, 23. Chronological Arrangement of the British Formations; Modern or Human Epoch; Post-Pliocene, 23. Tertiary Epochs, 24. Secondary Epochs, 25. Palæozoic Epochs, 30. Hypogene Rocks, 34. Volcanic Rocks, 35.

Chapter III.--On the Nature of Fossils or Organic Remains, 37. Incrustations, 38. Silicification, 40. Animal Remains, 43. Hints for Collecting Fossil Bones, 45.

II. Fossil Botany, 51

Chapter IV.--Fossil Botany, 51. Fossil Vegetables, 51. On the investigation of the Fossil Remains of Vegetables, 54. Endogenous Stems, 56. Exogenous Stems, 56. Structure of Coniferæ, 57. Botanical principles, 58. Exogens, 59. Endogens, 59. Investigation of Fossil Stems, 61. Fossil Leaves, 64. On the Microscopical Examination of Fossil Vegetables, 65. Mode of preparing slices of Fossil Wood, 66.

Chapter V.--On Peat-wood, Lignite, and Coal, 69. Submerged Forests; Peat, 70. Lignite, Brown-coal, Cannel-coal, 71. Bovey-coal, 72. Jet, 72. Wealden Coal, 73. Coal, 76. Stratification of a Coal-field, 80. Origin and Nature of Coal, 82.

Chapter VI.--Fossil Vegetables, 86. Fossil Cryptogamia, 87. Recent Diatomaceæ, 88. Fossil Diatomaceæ, 93. Fossil Coniferæ, 100. Fossil Fucoids, 101. Chondrites, 101. Moss-agates and Mocha-stones, 103. Equisetaceæ, 105. Calamites, 107. Filicites or Fossil Ferns, 109. Pachypteris, 112. Sphenopteris, 112. Cyclopteris, 114. Neuropteris, 115. Glossopteris, 115. Odontopteris, 116. Anomopteris, 116. Tœniopteris, 117. Pecopteris, 118. Lonchopteris, 119. Phlebopteris, 120. Clathropteris, 121. Stems of Arborescent Ferns, 122. Caulopteris, 123. Psarolites, 123. Sigillariæ and Stigmariæ, 125. Internal Structure of Sigillariæ, 130. Stigmaria, 132. Lepidodendron, 137. Lepidostrobus, 140. Triplosporite, 142. Lycopodites, 143. Halonia and Knorria, 143. Asterophyllites, 145. Sphenophyllum, 147. Cardiocarpon, 147. Trigonocarpum, 148. Fossil Cycadaceæ, 150. Pterophyllum, 152. Zamites, 152. Trunks and Stems of Cycadaceæ, 156. Mantellia, 157. Clathraria, 159. Endogenites, 163. Fossil Coniferæ, 164. Fossil Coniferous Wood, 167. Palæoxylon, 167. Pence, 168. Araucarites, 168. Sternbergia, 168. Petrified Forests of Conifers, 169. Coniferous Wood in Oxford Clay, 172. Coniferous Wood in Chalk, 173. Tertiary Coniferous Wood, 175. Fossil Foliage and Fruit of Coniferæ, 175. Araucaria, 175. Pinites, 176. Walchia, 177. Abietites, 178. Thuites, 180. Voltzia, 180. Taxites, 181. Nœggerathia, 181. Fossil Resins and Amber, 181. Fossil Palms, 183. Fossil Palm-leaves, 185. Fossil Fruits of Palms, 186. Fossil Fruits from the Isle of Sheppey, 186. Nipadites, 190. Fossil Fruit of Pandanus, 192. Wood perforated by Teredines, 193. Fossil Liliaceæ, 194. Fossil Fresh-water Plants, 195. Fossil Fruits of Chara, 195. Fossil Nymphaeæ, 197. Fossil Flowers, 197. Fossil Angiosperms, 197. Fossil Flora of Œningen, 200. Carpolithes, 202. Fossil Dicotyledonous Trees, 203. Dicotyledons of the Cretaceous Epoch, 205. Retrospect of Fossil Botany, 206. On Collecting British Fossil Vegetables, 211. British localities of Fossil Vegetables, 213.

III. Fossil Zoology, 216

Chapter VII.--Fossil Zoophytes; Porifera or Amorphozoa; Polypifera or Corals; Bryozoa or Molluscan Zoophytes, 218. Fossil Porifera, 219. On the Sponges in Chalk and Flint, 222. Spongites, 223. Fossil Zoophytes of Faringdon, 226. Scyphia, 227. Cnemidium, 228. Chenendopora, 228. Tragos, 229. Siphonia, 230. Choanites, 233. Paramoudra, 236. Clionites, 238. Spicula of Sponges, 238. Spiniferites, 239. Ventriculites, 242. Polype in Flint, 250. Fossil Polypifera, 251. Graptolites, 255. Fungia, 256. Anthophyllum, 257. Turbinolia, 257. Caryophillia, 257. Favosites, 258. Catenipora, 259. Springopora, 259. Lithostrotion, 260. Cyathophyllum, 260. Astræa, 262. Madrepora, 264. Millepora, 264. Lithodendron, 264. Gorgonia, 265. Fossil Bryozoa, 265. Flustra, 266. Crisia, 269. Retepora, 269. Fenestrella, 270. Petalæpora, 270. Pustulopora, 270. Homœsolen, 271. Idmonea, 271. Verticillipora, 273. Lunulites, 273. Geological Distribution of Fossil Zoophytes, 273. On Collecting Fossil Corals, 276. British localities, 278.

Chapter VIII.--Fossil Stelleridæ; comprising the Crinoidea and the Asteriadæ, 280. Crinoidea, 281. Pentacrinus, 282. Fossil Crinoidea, 283. Fossil Stems of Crinoidea, 284. Pulley-stones, 285. Apiocrinus, 288. Bourqueticrinus, 291. Encrinus, 292. Pentacrinites, 293. Actinocrinus, 295. Cyathocrinus, 295. Rhodocrinus, 297. Eugeniacrinus, 297. Pentremites, 297. Cystidea, 298. Marsupites, 299. Fossil Asteriadæ, 301. Fossil Ossicula of Star-Fishes, 303. Ophiura, 304. Goniaster, 306. Asterias, 307. Geological Distribution of the Crinoidea, 308.

Chapter IX.--Fossil Echinidæ, 311. Cidaritidæ, 314. Cidaris, 316. Diadema, 318. Echinus, 318. Salenia, 318. Spines of Cidarites, 319. Flint Casts of Cidarites, 320. Cidaritidæ of the Palæozoic Rocks, 321. Clypeasteridæ, 322. Galerites, 322. Holectypus, 324. Discoidea, 324. Clypeideæ, 325. Clypeus, 325. Nucleolites, 326. Spatangidæ, 326. Ananchytes, 327. Micraster, 328. Toxaster, 329. Holaster, 330. Geological Distribution of Echinites, 330. On Collecting and Developing Echinodermata, 331.

Chapter X.--Fossil Foraminifera; and Microscopical Examination of Chalk and Flint, 336. Foraminifera, 339. Classification of the Foraminifera, 342. Nummulites, 344. Orbitoides, 346. Siderolina, 346. Fusulina, 346. Nodosaria, 347. Cristellaria, 348. Flabellina, 348. Polystomella, 348. Lituola, 348. Spirolina, 349. Globigerina, 350. Nonionina, 350. Rotalia, 351. Rosalina, 351. Textularia, 352. Verneuilina, 352. Strata composed of Foraminifera, 352. Foraminifera of the Chalk and Flint, 355. Fossil Remains of the Soft Parts of Foraminifera, 357. Foraminifera-Limestones of India, 362. Foraminifera-deposit at Charing, 363. Foraminifera of the Oolite, Lias, &c. 364. Foraminifera-deposits of the United States, 364. Foraminifera of the Carboniferous Formations, 365. Foraminifera-Limestone of New Zealand, 366. Tertiary Foraminifera, 366. Foraminifera of the Fens of Lincolnshire and Cambridgeshire, 367. Recent Foraminifera-deposit at Brighton, 368. Geological Distribution of the Foraminifera, 369. Instructions for the Microscopical Examination of Chalk, Flint, and other Rocks, 371.

Chapter XI.--Fossil Testaceous Mollusks, or Shells, 374. Mollusca, 374. Acephala, 375. Encephala, 378. Fossil Bivalve Shells, 381. Shell-Rocks, 382. Fossil Brachiopoda, 388. Terebratula, 389. Spirifer, 390. Rhynchonella, 391. Pentamerus, 391. Orthis, Leptæna, and Productus, 392. Calceola, 392. Crania, 392. Orbicula, 392. Obolus, 392. Lingula, 393. Hippurites, 393. Fossil Shells of the Lamellibranchiates, 394. Monomyaria, 395. Ostrea, 395. Gryphæa, 396. Spondylus, 398. Plagiostoma, 399. Plicatula, 400. Pecten, 400. Inoceramus, 401. Avicula, 404. Dimyaria, 404. Venericardia, 405. Pectunculus, 405. Nucula, 406. Pinna, 406. Mytilus, 407. Modiola, 407. Pholadomya, 408. Pholas, 408. Teredo, 410. Trigonia, 412. Fossil Fresh-water Bivalves, 413. Unio, 414. Cyclas, 416. Fossil Pteropoda, 417. Fossil Gasteropoda, 417. Fresh-water Univalves, 421. Paludina, 421. Limnæus, 423. Planorbis, 423. Melanopsis, 424. Marine Univalves, 424. Fusus, 425. Pleurotoma, 425. Cerithium, 425. Potamides, 425. Rostellaria, 426. Dolium, 426. Trochus,426. Solarium, 426. Conus, 426. Pleurotomaria, 427. Euomphalus, 429. Murchisonia, 430. Sphærulites, 430. Molluskite, 432. Geological Distribution of Bivalve and Univalve Mollusks, 436. On the Collecting and Arranging Fossil Shells, 441. British Localities of Fossil Shells, 443.

CONTENTS OF VOL. II.

Description of Frontispiece (Plate II.)

List of Lignographs in Vol. II.

Table of Contents.

XVI. Fossil Reptiles; Enaliosaurians and Crocodiles, 643

Chapter XVII.--Fossil Reptiles; Dinosaurians, Lacertians, Pterodactyles, Turtles, Serpents, and Batrachians, 684.

IV. Geological Excursions, 827

Miscellaneous, 905.

General Index, 909.

DIRECTIONS TO THE BINDER.

Plate I.--Frontispiece to Vol. I.

Plate II. Frontispiece to Vol. II.

Plates III., IV., V., and VI., to follow the Table of Contents, and be placed opposite the description of each.

Lign. 247, to face page 770.

DESCRIPTION

OF THE

FRONTISPIECE OF VOL. I.

PLATE I.

Fig. 1.--A Fern in Coal-shale, from Leicestershire.

2.--A Crustacean in Limestone, from Solenhofen.

3.--A Fish (Pycnodus rhombus) in Limestone; from near Castel-a-mare.

4.--Half the Lower Jaw of a Hyena, from a fissure in a sandstone rock, near Maidstone.

5.--An Ammonite, from the Isle of Portland.

DESCRIPTION OF THE VIGNETTE OF VOL. I.

A Group of Fossils, containing

Ammonites Mantellii, from the Chalk-marl, Sussex. Turrilites costatus, from the Lower Chalk, Rouen. Chondrites Bignoriensis, from the Chalk-marl, Sussex. Echinus and Fusus, from Tertiary strata, Palermo.

DESCRIPTION OF PLATE II.

The Frontispiece of Vol. II.

A Fossil Fish of the Salmon tribe, allied to the Smelt; from the Chalk, near Lewes, in Sussex.

[See Vol. II. pages 626 and 628.]

DESCRIPTION OF PLATE III.

Incrustations, and Fossil Plants.

Figs. 1, 2, 3.--Twigs of Larch and Hawthorn, coated with tufa, or travertine, from having been exposed to the dripping of an incrusting spring; from Russia; see p. 39.

5.--A branch of recent Chara, with its fruit, with a thin pellicle of incrustation. Matlock.

6, 7.--Hazel-nuts, from Belfast Lough: fig. 6 is lined with crystals of calcareous spar; fig. 7 is filled with a solid mass of the same mineral; see p. 71.

4, 8.--Impressions of Dicotyledonous Leaves in Gypseous Marlstone, from Stradella, near Pavia; see p. 201.

9.--Eocene Lacustrine or Fresh-water Limestone, from East Cliff Bay, Isle of Wight, with stems and seeds of Charge: slightly magnified; see p. 195.

10.--Encrusted Twigs, from Matlock; the vegetable matter has perished, and left tubular cavities; see p. 39, and p. 873.

DESCRIPTION OF PLATE IV.

Various species of recent Diatomaceæ, to illustrate the Fossil remains of this Tribe of Vegetables.

For detailed descriptions, see pages 87-100.

Figs. 1 to 5.--Various kinds of Xanthidia: figs. 2, 3, 4, found in a pond on Clapham Common, and fig. 1. living in a pond near Westpoint, United States.

1.--Xanthidium furcatum: 1/24 of a line in diameter.

2.-- --------- hirsutum: 1/36.

3.-- --------- aculeatum: 1/24.

4.-- --------- fasciculatum: 1/24.

5.-- -------------------- variety of the above.

2*.--Pyxidicula operculata; Carlsbad, Bohemia: 1/48 of a line in diameter.

6.--Bacillaria vulgaris. 1/36 of a line in diameter. Pond on Clapham Common.

7.--Cocconeis scutellum: from the Baltic: 1/24 of a line.

8.--Navicula viridis: 1/6 of a line. Ponds on Clapham Common.

9.--The same; a side view; showing the currents produced in the water by the animal when in locomotion.

10.--Gallionella lineata: 1/36 of a line. Ponds on Clapham Common.

11.--Gallionella moniliformis: 1/72 of a line.

12.--Synhedra ulna: 1/9 of a line: the point a, marks the pedicle of attachment. Ponds on Clapham and Wandsworth Commons.

13.--Podosphenia gracilis: 1/12 of a line; attached to a thread of Calothria and having by self-division formed a radiating cluster. Common in the ditches communicating with the Thames in Battersea-fields.

14.--Navicula splendida: 1/12 of a line in diameter.

15.--Lateral view of the same.

16.--Eunotia turgida: 1/14 of a line; the empty shell, with sixty-five ribs, viewed laterally.

17.--A living group of the same: 1/20 of a line: a piece of Conferva rivularis, beset with these animalcules. The smaller species are E. Westermanni.

[All the above organisms were figured and described by Ehrenberg as animals (Polygastrica), and are comprised in his family Bacillaria; they are now, however, regarded as unquestionably vegetable structures, belonging to the family of Algæ, termed Diatomaceæ.]

DESCRIPTION OF PLATE V.

Illustrative of the Structure of Fossil Vegetables.

Fig. 1.--Polished transverse section of silicified Monocotyledonous Wood, from Antigua; p. 185.

1_a_.--Magnified 20 times linear.

1_b_.--Magnified 75 times linear.

2_a_.--Transverse section of silicified Coniferous Wood (Abies Benstedi) from the Kentish Rag, near Maidstone (Iguanodon quarry), × 120 linear; p. 173.

2_b_.--Vertical or longitudinal section of the same, × 250 linear.

3_a_.--Transverse section of calcareous coniferous wood, from Willingdon, Sussex, × 80 linear; p. 173.

3_b_.--Longitudinal section of the above, × 120 linear.

4.--Slice of a transverse section of a recent Dicotyledonous Stem; showing, 1st, Pith or medullary column, occupying the centre; 2d, Four bands of woody layers, separated by condensed lines of elongated tissue in series, and having large regular openings of vessels, with numerous medullary rays running continuously from the central pith to the bark; 3d, the bark. (From Mr. Witham.)

5.--Slice of a transverse section of a recent gymnospermous phanerogamic stem (of a Cycas), having a central pith, with woody layers separated by a condensed line, and consisting of elongated cellular tissue, arranged in a regular series; medullary rays and bark. (From Mr. Witham.)

6.--Bundles of vascular tissue in Stigmaria ficoides, × 12 linear. See p. 135. The two strands of vessels that appear as if on the surface (and are of a looser texture) are part of the vascular tissue of the stem, and become inflected (that is, bent over), and give rise to a band of vessels (the darker band seen between the above), that passes towards the bark or cortical covering.

7.--Portion of a transverse section of one of the bundles of vascular tissue of Sigillaria elegans, × 20 linear. (From M. Brongniart.) See p. 131.

The convex portion on the left, and which in the original stem is situated towards the centre, is composed of the medullary vascular tissue formed of vessels irregularly disposed.

The longitudinal bundles are the woody fibres arranged in a radiated circle: the smooth interspaces are medullary rays.

The two distinct roundish spots of vascular tissue on the right of the ligneous zone occur irregularly on the outside of the woody circle, and are supposed to be detached bundles of the ligneous zone extending towards the leaves. See p. 131.

DESCRIPTION OF PLATE VI.

Illustrative of the Structure of Fossil Teeth.

Fig. 1_a_.--Tooth of Psammodus porosus, from the Mountain Limestone. See p. 587.

1_b_.--Vertical section, a portion × 75 linear.

1_c_.--Transverse section of the same, × 75.

2_a_.--Tooth of Ptychodus polygurus, from the Chalk, near Lewes. See p. 585.

2_b_.--Portion of longitudinal section, × 20.

2_c_.--Portion of transverse section, × 20.

3_b_.--Tooth of the Labyrinthodon Jægeri, from the New Red sandstone near Wirtemberg; half the natural size: the specimen presented by Dr. Jæger. See p. 742.

3_a_.--A moiety of a transverse polished section, × 20.

3_b_.--Portion of a vertical section near the apex, × 20.

3_c_.--One of the anfractuosities of fig. 3_a_ × ×.

4_a_.--Crown or upper portion of a tooth of a young Iguanodon, from Tilgate Forest. See p. 697.

4_b_.--Portion of a vertical section of the above, × 20.

4_c_.--A small portion of a transverse section of the same, × 20.

5.--Tooth of Goniopholis, Tilgate Forest: half the natural size. See p. 678.

6_a_.--Tooth of a reptile (probably of the Hylæosaurus), from Tilgate Forest; half the natural size. See p. 690.

6_b_.--Portion of a vertical section of the same, × 20.

7_a_.--Tooth of Megalosaurus, from Tilgate Forest. See p. 687.

7_b_.--Portion of a vertical section of the same, × 10.

8.--A small portion of a vertical section of a tooth of Dendrodus. See p. 618.

9.--Portion of a transverse section of the base of a tooth of Ichthyosaurus, × 20. See p. 665.

10_a_.--Tooth of Lepidotus, Tilgate Forest. See p. 606.

10_b_.--The upper figure is a transverse section, and the lower a vertical section of the same, × 20.

LIST OF LIGNOGRAPHS IN VOL. I.

============

(Illustrative of Fossil Botany.)

LIGN. PAGE

1. Sections of Recent Vegetables 55 2. Sections of Fern-Stems 62 3. Nodule of Ironstone, enclosing a Fern Leaf 69 4. Siliceous Frustules of Diatomaceæ, and Spicules of Spongillæ 94 5. Fossil Gallionellæ 96 6. Organic Bodies in Porcelain Earth 97 7. Microphytes from the Tertiary deposits at Richmond, U.S. 98 8. Confervites Woodwardii 101 9. Chondrites Bignoriensis 102 10. Delesserites (Fucoides) Lamourouxii 103 11. Moss and Conferva in transparent quartz 104 12. Equisetum Lyellii 105 13. Equisetites columnaris 106 14. Calamites decoratus 107 15. Calamites in Coal-shale 108 16. Pecopteris Sillimani 110 17. Pachypteris lanceolata 112 18. Sphenopteris elegans 112 19. Sphenopteris nephrocarpa 113 20. Sphenopteris Mantellii 113 21. Cyclopteris trichomanoides 114 22. Neuropteris acuminata 115 23. Glossopteris Phillipsii 116 24. Odontopteris Schlotheimii 116 25. Anomopteris Mougeotii 117 26. Tœniopteris latifolia 118 27. Fig. 1, Pecopteris Murrayana 118 2, Pecopteris lonchitica 118 28. Lonchopteris Mantellii 119 29. Fig. 1, Phlebopteris Phillipsii 120 2, Phlebopteris propinqua 120 30. Clathropteris meniscoides 121 31. Caulopteris macrodiscus 123 32. Base of a Trunk of a Sigillaria, with root 126 33. Sigillariæ, in Coal Shale 128 34. Sigillaria Saullii 129 35. Silicified Stem of Sigillaria elegans 130 36. Stigmaria ficoides 133 37. Transverse section of Stigmaria ficoides 135 38. Erect Stem of a Sigillaria, with Roots 136 39. A Terminal Branch of a Lepidodendron 138 40. Lepidostrobi, the Fruit of Lepidodendra 141 41. Stems of Halonia and Knorria, from the Coal Formation 144 42. Asterophyllites equisetiformis 147 43. Fig. 1, Sphenophyllum Schlotheimii 148 2, Sphenophyllum erosum 148 44. Fossil Fruits, or Seed Vessels 149 45. Foliage and upper part of the Stem of Cycas revoluta (recent) 150 46. Part of a leaf of Pterophyllum comptum 152 47. Part of a leaf of Zamites pectinatus 153 48. Fruit of Zamites Mantellii 154 49. Fossil Fruits of Cycadeous Plants 156 50. Mantellia nidiformis 157 51. Mantellia cylindrica 158 52. Clathraria Lyellii, inner Axis of the Stem of 159 53. Clathraria Lyellii, Stem of 160 54. Clathraria Lyellii, part of Stem of 161 55. Clathraria Lyellii, Petiole of 161 56. Clathraria Lyellii, summit of Stem, with petioles 162 57. Clathraria Lyellii, water-worn Stem of 163 58. Fragment of Coniferous Wood in Flint 174 59. Fig. 1, Part of a Branch of Araucaria peregrina 176 2, Calamites nodosus, with foliage 176 60. Walchia hypnoides 178 61. Abietites Dunkeri 179 62. Thuites Kurrianus 180 63. Nipadites and other Fossil Fruits from the Isle of Sheppey 188 64. Fossil Fruits from the Isle of Sheppey 189 65. Fossil Wood perforated by Teredines 193 66. Fossil Fresh-water Plants 196 67. Fossil Fruits and Flower 198 68. Imprints of Dicotyledonous leaves in Gypseous Marlstone 201

(lllustrative of Fossil Zoology.)

69. Coral and Spongites 224 70. Fossil Zoophytes 227 71. Fossil Sponge 228 72. Fossil Zoophytes 229 73. Siphoniæ from the Greensand 231 74. Polypothecia dichotoma 232 75. Choanites Königi 234 76. Paramoudra in the Chalk 237 77. A group of Spiniferites in Flint 239 78. Spiniferites Reginaldi 241 79. Spiniferites palmatus 241 80. Flints, the forms of which are derived from Zoophytes 243 81. Ventriculites radiatus 244 82. Portions of Ventriculites 245 83. Ventriculites alcyonoides 248 84. A Coral Polype, in flint 250 85. Graptolites in Wenlock Limestone 255 86. Favosites polymorpha 258 87. Corals from the Dudley Limestone 261 88. Fossil Corals 262 89. Corals from the Chalk and Mountain Limestone 268 90. Stems of Encrinites and Pentacrinites 284 91. Recent Comatula and Fossil Crinoidea 286 92. Fossil Crinoidea 289 93. Apiocrinites 291 94. Actinocrinites and Pentacrinite 294 95. Cyathocrinites planus 296 96. Marsupites Milleri 300 97. Fossil remains of Star-fishes 305 98. Goniaster Mantelli 306 99. Asterias prisca 308 100. Fossil Turban Echinus with its Spines 311 101. Cidarites from the Oolite and Chalk 316 102. Fossil Spines of Cidarites 319 103. Echinital remains in flint 320 104. Echinites from the Chalk 323 105. Holectypus inflatus 324 106. Discoidea castanea 325 107. Micraster cor-anguinum 328 108. Toxaster complanatus 329 109. Foraminifera from the Chalk 342 110. Nummulites, or Nummulina 344 111. Foraminifera from the Chalk 347 112. Spirolinites in flint 349 113. Nonionina Germanica (recent) 350 114. Foraminifera in Chalk and flint 351 115. Chalk-dust, chiefly composed of Foraminifera 355 116. Section of a Rotalia in flint 356 117. Rotalia in flint, with the fossilized body of the animal in the shell 358 118. Soft Bodies of Foraminifera extracted from the Chalk 359 119. Remains of Foraminifera in chalk and flint 361 120. Fossil Oyster, from the Chalk 374 121. Recent Bivalve Mollusc, showing the several parts of the shell and the animal 377 122. Turritellæ from Bracklesham 383 123. Shell-Conglomerate 385 124. Shell-Limestone, from the mouth of the Thames 386 125. Terebratula and Rhynchonella 388 126. Terebratula and Spirifer 390 127. Shells and Echinite from the Oolite and Lias 397 128. Spondylus spinosus in Chalk-flint 399 129. Inoceramus Cuvieri of the Chalk 401 130. Flint with fragments of Inoceramus perforated by Clionites 403 131. Unio Valdensis 415 132. Cyclas and Melanopsis 416 133. Fossil Shells of Gasteropoda 418 134. Polished Slab of Purbeck Marble 422 135. Univalves from the Chalk of Touraine 427 136. Univalves from the Mountain Limestone 428 137. Murchisonia bilineata 430 138. Sphærulites from the Chalk 431 139. Coprolites and Molluskite 432

THE

MEDALS OF CREATION.

⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼

Introduction

"Geology, in the magnitude and sublimity of the objects of which it treats, ranks next to Astronomy in the scale of the Sciences."--Sir J. F. W. Herschel.

Geology, a term signifying a discourse on the Earth, (from two Greek words: viz. γἡ, ge, the earth; and λὁγος, logos, a discourse,) is the science which treats of the physical structure of the planet on which we live, and of the nature and causes of the successive changes which have taken place in the organic and inorganic kingdoms, from the remotest period to the present time, and is therefore intimately connected with every department of natural philosophy.

While in common with other scientific pursuits it yields the noblest and purest pleasures of which the human mind is susceptible, it has peculiar claims on our attention, since it offers inexhaustible and varied fields of intellectual research, and its cultivation, beyond that of any other science, is in a great measure independent of external circumstances; for it can be followed in whatever condition of life we maybe placed, and wherever our fortunes may lead us.

The eulogium passed by a distinguished living philosopher on scientific knowledge in general, is strikingly applicable to geological investigations. "The highest worldly-prosperity, so far from being incompatible with them, supplies additional advantages for their pursuit; they may be alike enjoyed in the intervals of the most active business, while the calm and dispassionate interest with which they fill the mind, renders them a most delightful retreat from the agitations and dissensions of the world, and from the conflict of passions, prejudices, and interests, in which the man of business finds himself continually involved."[2]

[2] Sir J. F. W. Herschel, "Discourse on the Study of Natural Philosophy."

From the present advanced state of geological science, particularly of that department which it is the more especial object of these volumes to elucidate, namely Palæontology,[3] or the study of Organic Remains,--it seems scarcely credible, that but little more than a century ago it was a matter of serious question with naturalists, whether the petrified shells imbedded in the rocks and strata were indeed shells that had been secreted by molluscous animals; or whether these bodies, together with the teeth, bones, leaves, wood, &c. found in a fossil state, were not formed by what was then termed the plastic power of the earth; in like manner as minerals, metals, and crystals.

[3] Palæontology: from παλαιος, palaios, ancient--οντα, onta, beings--λὁγος, logos, a discourse.

In a "Natural History of England," published towards the end of the last century, it is gravely observed that at Bethersden in Kent, a kind of stone is found full of shells, "which is a proof that shells and the animals we find in them living, have no necessary connexion." Another amusing instance of the ignorance on such subjects which prevailed at no remote period, occurs in a "History of the County of Surrey," in which it is stated that in a search for coal near Guildford the borers broke, and "this was thought by Mr. Peter Lely, the Astrologer, to have been the work of subterranean spirits, who wrenched off the augers of the miners, lest their secret haunts should be invaded."

But in the latter part of the seventeenth century, there were several eminent men in England who were greatly in advance of the age in which they lived, and strenuously exerted themselves to discover and promulgate the true principles of Geology. Among these, Dr. Martin Lister, physician to Queen Anne, was one of the most distinguished. This accomplished naturalist, in his great work on shells, which remains to this day a splendid monument of his labours, and of the talents and filial affection of his two daughters, by whom all the plates were engraved, figures and describes many fossil shells as real animal productions, and carefully compares them with recent species. He also recognised the distinction of strata by the organic remains they contain; and to him the honour is due of having first suggested the construction of geological maps;[4] he was likewise well acquainted with the position and extent of the Chalk and other strata of the South of England.[5]

[4] See Notes on the Progress of Geology in England, by W. H. Fitton, M.D. &c. Philos. Mag. vols. i. and ii. for 1832 and 1833.

[5] This celebrated physician and British geologist died in 1712, and was interred in the old church at Clapham; where a tablet to his memory is affixed to the outside of the north wall of St. Paul's Chapel.

From the foreign writers, who at an early period had obtained some correct notions of the structure of our planet, and of the nature of the revolutions it had undergone, I select the following beautiful and philosophical illustration of the physical mutations to which the surface of the earth is perpetually subjected. It is from an Arabic manuscript of the thirteenth century;[6] the narrative is supposed to be related by Rhidhz, an allegorical personage.

[6] Quoted by Sir C. Lyell in his "Principles of Geology."

"I passed one day by a very ancient and populous city, and I asked one of its inhabitants how long it had been founded? 'It is, indeed, a mighty city,' replied he; 'we know not how long it has existed, and our ancestors were on this subject as ignorant as ourselves.' Some centuries afterwards I passed by the same place, but I could not perceive the slightest vestige of the city; and I demanded of a peasant, who was gathering herbs upon its former site, how long it had been destroyed? 'In sooth, a strange question,' replied he, 'the ground here has never been different from what you now behold it.' 'Was there not,' said I, 'of old a splendid city here?' 'Never,' answered he, 'so far as we know, and never did our fathers speak to us of any such.'

"On revisiting the spot, after the lapse of other centuries, I found the sea in the same place, and on its shores were a party of fishermen, of whom I asked how long the land had been covered by the waters? 'Is this a question,' said they, 'for a man like you? this spot has always been what it is now.'

"I again returned ages afterwards, and the sea had disappeared. I inquired of a man who stood alone upon the ground, how long ago the change had taken place, and he gave me the same answer that I had received before.

"Lastly, on coming back again, after an equal lapse of time, I found there a flourishing city, more populous and more rich in buildings than the city I had seen the first time; and when I fain would have informed myself regarding its origin, the inhabitants answered me, 'Its rise is lost in remote antiquity--we are ignorant how long it has existed, and our fathers were on this subject no wiser than ourselves.'"

We may smile at the ignorance of the inhabitants of the fabled cities, but are we in a condition to give a more satisfactory reply should it be inquired of us, "What are the physical changes which the country you inhabit has undergone?"--and yet cautious observation, and patient and unprejudiced investigation, are alone necessary to enable us to answer the interrogation.

Dismissing from his mind all preconceived opinions, the student must be prepared to learn that the earth's surface has been, and still is, subject to perpetual mutation,--that the sea and land are continually changing place,--that what is now dry land was once the bottom of the deep, and that the bed of the present ocean will, in its turn, be elevated above the water and become land,--that all the solid materials of the globe have been in a softened, fluid, or gaseous state,--that the relics of countless myriads of animals and plants are entombed in the rocks and strata,--and that vast mountain-chains, and extensive regions, are wholly composed of the petrified remains of beings that lived and died in periods long antecedent to the creation of the human race. Astounding as are these propositions, they rest upon evidence so clear and incontrovertible, that they cannot fail to be admitted by every intelligent and unprejudiced reader, who will bestow but a moderate share of attention to the examination of the phenomena, of which the following pages present a familiar exposition.

I cannot conclude these introductory observations, without adverting to the incalculable benefits which result from scientific pursuits in general, and of Geology in particular. An able modern writer has justly remarked:--"It is fearfully true, that nine-tenths of the immorality which pervades the better classes of society, originate from the want of an interesting occupation to fill up the vacant time; and as the study of the natural sciences is as attractive as it is beneficial, it must necessarily exert a moral and even religious influence upon the young and inquiring mind. The youth who is fond of scientific pursuits will not enter into revelry, for frivolous or vicious excitements will have no fascination for him. The overflowing cup, the unmeaning or dishonest game, will not entice him. If any one doubts the beneficial influence of these studies on the morals and character, I would ask him to point out the immoral young man who is devotedly attached to any branch of natural science: I never knew such an one. There may be such individuals--for religion only can change the heart--but if there be, they are very rare exceptions; and the loud clamours which are always raised against the man of science who errs, prove how rarely the study of the works of the Creator fails to exert an ennobling effect upon a well-regulated mind. Fortunate, indeed, are the youth of either sex, who early imbibe a taste for natural knowledge, and whose predilections are not thwarted by injudicious friends."

And while Geology exerts this hallowing influence on the character, it possesses the great advantage of presenting subjects adapted to every capacity; on some of its investigations the highest intellectual powers and the most profound acquirements in exact science are required; while many of its problems may be solved by any one who has eyes and will use them; and innumerable facts illustrative of the ancient condition of our planet, and of its inhabitants, may be gathered by any diligent and intelligent observer.

But it is surely unnecessary to dwell on the interest and importance of a study, which instructs us that every pebble we tread upon bears the impress of the Almighty's hand, and affords evidence of Creative wisdom; that every grain of sand, every particle of dust scattered by the wind, may be composed of the aggregated skeletons of beings, so minute as to elude our unassisted vision, but which possessed an organization as marvellous as our own;--a science whose discoveries have realized the wildest imaginings of the poet,--whose realities far surpass in grandeur and sublimity the most imposing fictions of romance;--a science, whose empire is the earth, the ocean, the atmosphere, the heavens;--whose speculations embrace all elements, all space, all time;--objects the most minute, objects the most colossal;--carrying its researches into the smallest atom which the microscope can render accessible to our visual organs,--and comprehending all the phenomena in the boundless Universe, which the powers of the telescope can reveal.

And as no branch of natural philosophy can more strongly impress the mind with that deep sense of humility and dependence, which the contemplation of the works of the Eternal is calculated to inspire, so none can more powerfully encourage our aspirations after truth and wisdom. Every walk we take offers subjects for profound meditation,--every pebble that attracts our notice, matter for serious reflection; and contemplating the incessant dissolution and renovation which are taking place around us in the organic and inorganic kingdoms of nature, we are struck with the force and beauty of the exclamation of the poet--

My heart is awed within me, when I think Of the great miracle which still goes on In silence round me--the perpetual work Of Thy Creation, finished, yet renewed For ever!

PRELIMINARY REMARKS.

ON THE PLAN OF THE WORK, AND THE ARRANGEMENT AND SUBDIVISION OF THE SUBJECTS IT EMBRACES.

With the view of economizing space, I would refer the reader to the following volumes for figures and descriptions of such fossils as are illustrated therein: by this arrangement I hope to afford the student a comprehensive view of Palæontology, and yet restrict this work within the limits which as a manual it would be inconvenient to exceed; at the same time it will be complete in itself, and afford all the information required by the amateur collector and general reader.

I. Dr. Buckland's Bridgewater Treatise: 2 vols. 8vo.--These volumes contain numerous excellent figures of organic remains; and as the work is, or ought to be, found in every good public or private library in the kingdom, it will be accessible to most of my readers.

II. The Wonders of Geology, or a Familiar Exposition of Geological Phenomena; sixth edition, in two vols, with coloured plates, and numerous figures; by the Author. Price 18_s._--This work is designed to afford a general view of Geological phenomena, divested as much as possible of scientific language: it is illustrated by numerous figures of organic remains.

III. Geological Excursions round the Isle of Wight and along the adjacent Coasts of Hampshire and Dorsetshire. One volume, richly illustrated. By the Author. Price 12_s._

IV. Petrifactions and their Teachings; or a Hand-book to the Gallery of Organic Remains in the British Museum. One vol. with many original figures of the most interesting objects. By the Author.[7] Price 5_s._

[7] The three works above named consist of four volumes uniform with the present edition of the "Medals of Creation:" this series of six volumes comprises the popular geological works of the Author.

V. A Pictorial Atlas of Fossil Remains; consisting of Coloured Illustrations selected from "Parkinson's Organic Remains of a Former World," and Artis' "Antediluvian Phytology." 1 vol. 4to. with seventy-four coloured plates, and several lignographs, containing nearly 900 figures of fossils. By the Author. Price 2_l._ 2_s._

To the above may be added Dana's Mineralogy, which treats of the various mineral substances that enter into the composition of the rocks and strata in which the fossil remains are imbedded.

A good geological map of Great Britain is indispensable. The small map published by the Society for the Diffusion of Useful Knowledge, edited by Sir R. Murchison, price 5_s._, is an excellent compendium; but Mr. Knipe's large "Geological Map of the British Isles" is the most complete and convenient for the traveller: price 3_l._ 3_s._ By reference to the map, the geological structure, and the prevailing fossils of a district, may be ascertained.

The above works are referred to as follows: viz.

Bd. Dr. Buckland's Treatise.

Wond. The Wonders of Geology.

Geol. I. of W. Geology of the Isle of Wight.

Petrifactions. Petrifactions and their Teachings.

Pict. Atlas. Pictorial Atlas of Organic Remains.

The following works, to which reference will often be made, are thus denoted:--

Foss. Flor. The Fossil Flora of Great Britain, by Dr. Lindley, and W. Hutton, Esq. 3 vols. 8vo.

Vég. Foss. Histoire des Végétans: Fossiles, par M. Adolphe Brongniart. 1 vol. 4 to.

Geol. Trans. Transactions of the Geological Society of London. 5 vols. 4to.; and New Series, in 5 vols.

Geol. Proc. Geological Proceedings.

---- Journ. ---------- Quarterly Journal.

Sil. Syst. The Silurian System, by Sir R. I. Murchison. 2 vols. 4to. with plates and map.

Org. Rem. Parkinson's Organic Remains of a Former World. 3 vols. 4to.

Oss. Foss. Ossemens Fossiles, par Baron Cuvier. 5 vols. 4to. 5^{me.} edit.

Min. Conch. Sowerby's Mineral Conchology. 6 vols. 8vo.

Odont. Odontography; a Treatise on the Comparative Anatomy of the Teeth, by Professor Owen. 2 vols. 8vo.

Brit. Mam. British Fossil Mammalia; by the same Author. 1 vol. 8vo.

Brit. Rep. Reports on British Fossil Reptiles in the British Association Transactions for 1839, and 1841; by the same Author.

Phil. York. Geology of Yorkshire, by Professor John Phillips. 2 vols. 4to.

South. D. Fossils of the South Downs, 1 vol. 4to. 42 plates by the Author. 1822.

Geol. S. E. Geology of the South-east of England. 1 vol. 8vo. by the same.

Tilg. For. Fossils of Tilgate Forest. 1 vol. 4to. 20 plates; by the same. 1827.

Poiss. Foss. Recherches sur les Poissons Fossiles, par M. Agassiz. 4 vols. 4to, and 2 vols, folio.

Man. Geol. Manual or Elements of Geology, by Sir C. Lyell. 1 vol. 8vo. Edit. 1852.

The following abbreviations are also employed:--

§ 1. Relative to the Rocks or Strata.

Drift. Alluvial deposits, or Drift.

Tert. Tertiary. Lond. C. London clay.

Cret. Cretaceous formation. U. Ch. Upper chalk. L. Ch. Lower chalk.

Trias. New Red Sandstone, or Triassic deposits.

Carb. Carboniferous or Coal formation.

Mt. L. Mountain or Carboniferous limestone.

Devon. Devonian or Old Red Sandstone formation.

Sil. Syst. Silurian System, or formation.

§ 2. Relative to Organic Remains.

nat. Natural size.

× Magnified in diameter: e.g. × 8, magnified eight diameters, &c.

× × Highly magnified; the degree not accurately determined.

inv. Invisible to the naked eye.

-- Less than natural: e.g. --2/3, reduced to two-thirds the diameter of the original.

Lign. Lignograph or woodcut.

Explanation of Terms.--Upon the occurrence of a scientific word apparently requiring explanation, the meaning, where practicable, is for the most part given in a parenthesis; for example, Caulopteris (fern-stem); Phascotherium (pouch-animal); carboniferous (coal-bearing); except in the case of arbitrary names, and of those whose derivation cannot be concisely expressed.[8] With the view of rendering these volumes more generally useful, English terminology is in many instances made use of, though involving inelegance of expression.

[8] Upwards of 300 scientific terms are explained in the Glossary, "Wonders," vol. ii. p. 915-921.Return to passage

The work is divided into four parts: the first is an Introduction to the Study of Organic Remains; the second treats of Fossil Botany; the third embraces Fossil Zoology; and the fourth, under the head of Geological Excursions, illustrates the principles enunciated in the course of the work, by practical observations on a few instructive British localities.

Part I

1. On the British Strata and their Fossils.

2. Arrangement and Characters of the British Formations.

3. On the Nature of Fossils or Organic Remains.

4. On Mineralized Vegetable Remains, and the mode of conducting their investigation.

5. On Peat, Lignite, and Coal.

II. FOSSIL BOTANY

Classification of Fossil Vegetables.

1. On the Fossil Remains of Cryptogamiæ. 2. " " Diatomaceæ. 3. " " Ferns. 4. " " Sigillariæ. 5. " " Lepidodendra. 6. " " Cycadaceæ. 7. " " Coniferæ. 8. " " Palms. 9. " " Angiosperms.

Retrospect.

British Localities of Fossil Plants.

III. FOSSIL ZOOLOGY

On the Fossil Remains of the Animal Kingdom.

1. Zoophytes; Amorphozoa. 2. " Polypifera. 3. Echinoderms; comprising the a. Crinoidea, or Lily-shaped animals. b. Asteriada, or Star-Fishes. c. Echinida, or Sea-Urchins. 4. Foraminifera. 5. Shell-bearing Mollusca. 6. Articulated animals; comprising a. Crustaceans. b. Insects. 7. Fishes. 8. Reptiles. 9. Birds. 10. Mammalia. 11. Man.

Retrospect.

Part IV

I. Geological Excursions in various parts of England, illustrative of the method of observing geological phenomena, and of collecting Fossil Remains.

II. Miscellaneous. On the prices of Fossils; lists of Dealers, &c.

II. Appendix.

Part I

⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼

Chapter I

ON THE NATURE AND ARRANGEMENT OF THE BRITISH STRATA, AND THEIR FOSSILS.

"To discover order and intelligence in scenes of apparent wildness and confusion is the pleasing task of the geological inquirer."--Dr. Paris.

The solid materials of which the earth is composed, from the surface to the greatest depths within the reach of human observation, consist of minerals and fossils.

Minerals are inorganic substances formed by natural operations, and are the product of chemical or electro-chemical action.

Fossils are the durable remains of animals and vegetables which have been imbedded in the strata by natural causes in remote periods, and subsequently more or less altered in structure and composition by mechanical and chemical agencies.

The soft and delicate parts of animal and vegetable organisms rapidly decompose after death; but the firmer and denser structures, such as the bones and teeth of the former, and the woody fibre of the latter, possess considerable durability, and under certain conditions will resist decay for many years, or even centuries; and when deeply imbedded in the earth, protected from atmospheric influences, and subjected to the conservative effects of various mineral solutions, the most perishable tissues often resist decomposition, and becoming transformed into stone, may endure for incalculable periods of time. The calcareous and siliceous cases or frustules of numerous microscopic plants are so indestructible, and occur in such inconceivable quantities, that the belief of some eminent naturalists of the last century, that every grain of flint and lime in certain rocks, may have been elaborated by the energies of vitality, can no longer be regarded as an extravagant hypothesis. Some idea may be formed of the large proportion of the solid materials of the globe that has unquestionably originated from this source, by a reference to the list of strata which are wholly, or in great part, composed of animal and vegetable structures, given in the "Wonders of Geology," p. 888.

There are also immense tracts of country that consist in a great measure of the remains of plants in the state of anthracite, coal, lignite, &c.; and districts covered with peat-bogs and subterranean forests.

Although these relics of animal and vegetable organisms are found in almost every sedimentary deposit, yet they occur far more abundantly, and in a better state of preservation, in some strata than in others: nor are they equally distributed throughout the same bed, but are heaped together in particular localities, and occur but sparingly, or are altogether absent, in other layers of the same rock. Neither are the remains of the same kinds of animals and plants found indiscriminately in strata of different ages: on the contrary, many species are restricted to the most ancient, others to the most recent formations; while some genera range through the entire series of deposits, and also appear as denizens of the existing seas. Hence organic remains acquire a high degree of importance, not only from the intrinsic interest they possess as objects of natural history, but also for the light they shed on the physical condition of our planet in the remotest ages, and for the data they afford as to the successive physical revolutions which the surface of the earth has undergone.

Fossils have been eloquently and appropriately termed Medals of Creation; for as an accomplished numismatist, even when the inscription of an ancient and unknown coin is illegible, can from the half-obliterated effigy, and from the style of art, determine with precision the people by whom, and the period when, it was struck; in like manner the geologist can decipher these natural memorials, interpret the hieroglyphics with which they are inscribed, and from apparently the most insignificant relics, trace the history of beings of whom no other records are extant, and ascertain the forms and habits of unknown types of organization whose races were swept from the face of the earth, ere the creation of man and the creatures which are his contemporaries. Well might the illustrious Bergman exclaim, "Sunt instar nummorum memorialium, quæ de præteritis globi nostri fatis testantur, ubi omnia silent monumenta historica."

To derive from these Medals of Creation all the information they are capable of affording, regard therefore must be had not only to their peculiar characters, but also to the geological relations of the strata in which they are imbedded. Data may be thus obtained by which the relative age of a formation or group of strata can be determined, as well as the mode of deposition, and the agency by which it was effected; whether in the bed of an ocean, or of a lake, or estuary,--by the action of the sea, or of rivers, or running streams,--by the effects of icebergs or glaciers,--by slow processes through long periods of time, or by sudden inundations or deluges,--or by the agency of volcanoes and earthquakes.

The discovery that particular fossils are confined to certain deposits, was soon productive of important results, which greatly tended to the advancement of modern Geology; for although Dr. Lister, more than a century before, had obtained a glimpse of this law, its principles were neither understood nor regarded in this country until the late Dr. William Smith, by his own unaided exertions, proved by numerous observations on the British strata, its value and applicability for the identification of a deposit, in districts remote from each other.

This phenomenon did not escape the notice of the distinguished French philosophers, MM. Cuvier and Brongniart, who in their admirable work, "Géographie Minéralogique des Environs de Paris," enunciated the same principle:--

"Le moyen que nous avons employé pour reconnoitre au milieu d'un si grand nombre de lits calcaires, un lit déjà, observé, dans un canton très-éloigné, est pris de la nature des fossiles renfermés dans chaque couche; ces fossiles sont toujours généralement les mêmes dans les couches correspondantes, et présentent d'un système de couche à un autre système, des différences d'espèces assez notables. C'est un signe de reconnoissance qui jusqu'à présent ne nous a pas trompés."[9]

[9] Géog. Min. Oss. Foss. tom. ii. p. 266.

Now, though recent discoveries have shown that this rule has many exceptions, and that its too stringent adoption has been productive of some erroneous generalizations, yet if employed with due caution it is fraught with the most interesting results, and is the only certain basis of our knowledge respecting the appearance, continuance, and extinction, of the lost races of animals and plants, which were once denizens of our planet.

[Sidenote: ROCKS AND STRATA.]

In the "Wonders of Geology" will be found a comprehensive sketch of the composition and arrangement of the several formations or groups of strata; and a reference to that work will afford the student the necessary information on this branch of Geology. For the convenience of the general reader I subjoin a synoptical view of the characters and relations of the British fossiliferous deposits.

The total thickness of the entire series of rocks within the scope of human examination, is estimated at from fifteen to twenty miles, reckoning from the summits of the highest mountains to the greatest depths hitherto penetrated; and as this vertical section scarcely amounts to 1/400th of the diameter of the globe, it is familiarly termed the Earth's crust. The substances of which the sedimentary strata are composed have been deposited by the action of water, and subsequently more or less modified in structure and composition by heat, and by electro-chemical forces. The superficial accumulations of water-worn detritus, consisting of gravel, boulders, sand, clay, &c. are termed Drift, or Alluvial deposits. When the successive layers in which the sediments subsided are obvious, the deposits are said to be stratified; when the nature of the materials has been altered by igneous action or high temperature, but the lines of stratification are not wholly effaced, the rocks are denominated metamorphic (transformed). When all traces of organic remains and of sedimentary deposition are lost, and the mass is crystalline, and composed of known products of igneous action, such rocks are named plutonic, as granite, sienite, trap, basalt, porphyry, and the like. Lastly, rocks resembling the lavas, scoria, and other substances emitted by burning mountains still in activity, are called volcanic.

The sedimentary origin ascribed to ancient crystalline rocks is, of course, hypothetical, since all evidence of aqueous deposition is wanting, and the minerals (mica, quartz, and felspar) of which they are so largely constituted, are not readily soluble in water under ordinary circumstances. But rocks unquestionably deposited by water, when exposed to intense heat under great pressure, acquire a crystalline structure (Wond. p. 864); and a series of changes, from a loose earthy deposit, to compact volcanic lava, may be traced in numerous instances, so as to leave but little doubt that the rocks called primitive or primary, may have originally been either argillaceous, siliceous, or calcareous strata, abounding in organic remains (Wond. p. 873). These crystalline masses have been formed at successive periods; for granite is found of all ages, occurring in the most ancient, as well as in comparatively modern epochs. The difference between the composition and aspect of these rocks, and those of recent volcanoes, is with much probability ascribed to the fact that the latter are of sub-aerial origin; that is, were erupted on the surface, and the gaseous products in consequence escaped; while the former were ejected at great depths, either beneath the sea, or under immense accumulations of other deposits, and being thus subjected to great pressure, the volatile elements were confined, and formed new combinations: in like manner as chalk when burnt in the open air is converted into lime, the carbonic acid gas escaping; but when exposed to the same degree of heat in a closed iron tube, is transformed into granular marble (Wond. p. 104).

From these ancient crystalline rocks generally underlying the sedimentary deposits, and never appearing as if they had been ejected from a crater, the term hypogene[10] (nether-formed) is employed by Sir C. Lyell to designate the whole class; and they are subdivided into, 1. plutonic, those in which all traces of sedimentary origin are lost, as granite; and 2. metamorphic, those which still manifest traces of stratification, as mica-schist, &c.

[10] Nether-formed, from ιπο, hypo, under; and γἱνομαι, ginomai, to be formed.

The fossiliferous rocks are, for the convenience of study, separated into three grand divisions.

1. The Tertiary; comprising the deposits between the Chalk and the superficial Drift and modern Alluvium.

2. The Secondary; from the Chalk to the Trias or New Red, inclusive.

3. The Palæozoic; from the Permian to the Silurian; including the vast series of unfossiliferous slate rocks termed the Cambrian, in which all traces of organic remains are lost.

In the following arrangement the strata are enumerated as if lying in regular sequence, one beneath the other; but in nature such an unbroken series has never been observed. A few groups only occur in a serial order, and these but rarely in their original position. The beds are for the most part disrupted, and lie in various angles of inclination; sometimes they are completely retroverted, the newer strata underlying those upon which they were originally deposited. The order of succession has been ascertained by careful observation of the relative superposition of the respective members of the series in different countries; and from an immense number of facts collected by able observers in every part of the globe.

This synopsis presents a chronological arrangement of the rocks according to the present state of geological knowledge, but it must not be supposed that these rigid distinctions, these hard lines, which are necessary to facilitate the acquisition of a general idea of the phenomena attempted to be explained, exist in nature. By whatever names we designate geological periods, there appear to be no clearly defined boundaries between them in reference to the whole earth: such well marked lines may be seen in particular localities, but daily experience teaches us that there is a blending, and a gradual and insensible passage, from the lowest to the highest sedimentary strata, particularly in respect of fossil remains. The terms employed to designate formations can only be considered as expressing the predominance of certain characters, to be used provisionally, as a convenient mode of classifying and generalizing the facts collected, whilst that knowledge is accumulating which in after times will reveal the nature and order of succession of the principal events in the earth's physical history.[11]

[11] "Wonders of Geology," p. 892.Return to passage

Dr. Buckland's "Bridgewater Treatise" (Vol. II. frontispiece) contains a comprehensive Diagram of the rocks and strata of which the crust of the earth is composed; it was drawn by the late Mr. Thomas Webster.

II. SYNOPSIS OF THE BRITISH STRATA

"Hard lines are admissible in Science, whose object is not to imitate Nature, but to interpret her works."--Greenough.

The classification of the stratified rocks is based on three principal characters; namely, 1, the mineral structure; 2, the order of superposition; and 3, the nature of the organic remains; the following synopsis has been drawn up in accordance with these principles.[12]

[12] See "Wonders of Geology," vol. i. pp. 200-207, for a Synoptical Table of the principal rocks.

CHRONOLOGICAL ARRANGEMENT OF THE BRITISH FORMATIONS.

COMMENCING WITH THE UPPERMOST OR NEWEST DEPOSITS.

Modern or Human Epoch.

Alluvial Deposits: remains of Man and existing species of mammalia.

Post-Pliocene.

Drift; Boulder clay; Till; &c. comprising the superficial irregular accumulations of transported materials, consisting of gravel, boulders, sand, clay, &c.

Observations.--These beds have been formed by a variety of causes; by land-floods and inundations, by irruptions of the sea, and by the agency of glaciers and icebergs. They are the catacombs of the extinct colossal mammalia--of the mastodon, mammoth, rhinoceros, hippopotamus, elk, horse, ox, whale, &c. They cannot be definitively separated from those of the Modern or Human epoch, for the gravel beds near Geneva, which closely resemble the newest tertiary drift in materials and position, abound in bones of animals, almost all of which belong to existing species.[13]

[13] See M. Pictet's "Palæontologie."

Tertiary Epochs.

An extensive series, comprising many isolated groups of marine and lacustrine deposits, containing fossil remains of animals and vegetables of all classes; the greater number of genera and species in the most ancient or lowermost beds belong to extinct types.

Subdivisions:--

1. The Pliocene[14] (more new, or recent.[15] Wond. p. 221); strata in which the shells are for the most part of recent species, having only about ten per cent of extinct forms. (Norwich Crag.)

2. The Miocene (less recent,[16] Wond. p. 221); containing about 20 per cent of recent species of shells. (Suffolk Crag.)

3. The Eocene (dawn of recent,[17] in allusion to the first appearance of recent species--Wond. p. 226); the most ancient tertiary strata contain but very few existing species of shells; not more than five per cent. (London, Hants, and Paris basins.)

[14] In the present state of our knowledge, this arrangement is of great utility, but it will probably require considerable modification, and must, perhaps, hereafter be abandoned; for it cannot be doubted, that strata in which no recent species have yet been found, may yield them to more accurate and extended observations, and those in which only a few recent species are associated with a large number of extinct forms, may have these proportions reversed.

[15] From πλειων, pleion, more; and καινος, kainos, recent.

[16] From μεἱων, meion, less, and recent.

[17] From ἠως, eos, the dawn or commencement, and recent.

Obs.--The marine are often associated with fresh-water deposits, and the general characters of the Tertiary system are alternations of marine and lacustrine strata. In England the most important Tertiary deposits are those of the London basin, the Isle of Sheppey, the south-western coasts of Sussex and Hampshire, the north of the Isle of Wight, and the eastern coasts of Essex, Norfolk, Suffolk. (Wond. p. 226.)

Secondary Epochs.

The Cretaceous or Chalk Formation. (Wond. p. 296). A marine formation, comprising a vast series of beds of limestone, sandstone, marl, and clay, &c.; characterized by remains of extinct zoophytes, mollusks, cephalopods, echinoderms, crustaceans, fishes, &c.; lacertians, crocodilians, chelonians, and other extinct reptiles; drifted coniferous and dicotyledonous wood and foliage, fuci, &c.

Subdivisions:--

1. The Maestricht beds. Friable coralline and shelly limestones, with flints and chert.

2. Upper Chalk, with flints } Craie blanche of the French } geologists. 3. Lower Chalk, without flints }

4. Chalk-marl Craie tufeau.

5. Firestone, Malm-rock, Upper } Glauconie crayeuse. Greensand, or Glauconite }

6. Galt, or Folkstone-marl Glauconie sableuse.

7. Shanklin, or Lower Greensand. { Formation néocomien; which { is divided into N. supérieur, { the English upper divisions { of the Greensand or Kentish { rag; and N. inférieur, the { lower beds of sand and clay, { of the southern shore of the { Isle of Wight, at Atherfield.[18]

[18] Another subdivision, with other names (chiefly derived from French localities), has lately been proposed by M. D'Orbigny; which I notice with the more regret, since this eminent naturalist formerly repudiated the censurable practice of many modern systematists, of changing established names of strata and fossils, without any just cause. The British geologist will smile to see the Wealden Formation--so eminently distinguished in England and Germany by its extent, thickness, and remarkable fauna and flora,--ranked as a subordinate member of the "Formation néocomien," of France.

Obs.--The Maestricht beds are chiefly composed of fawn-coloured limestones of friable texture; containing peculiar species of corals, shells, fishes, reptiles, &c. The Chalk is generally white, but in some localities is of a deep red, in others of a yellow colour; nodules, layers, and veins of flint occur in the upper, but are seldom present in the lower chalk. The Marl is an argillaceous limestone, which generally prevails beneath the white chalk; it sometimes contains a large intermixture of green or chlorite sand, and then is called Firestone, or Glauconite. The Galt is a stiff, blue or blackish clay, abounding in shells which frequently retain their pearly lustre. The Greensand is a triple alternation of sands and sandstones with clays; and beds of cherty limestone called Kentish Rag.

The Wealden; a formation, whose fluviatile character was first observed and established by the researches of the author (Wond. p. 360). A series of clays, sands, sandstones and limestones, with layers of lignite, and extensive coal-fields; characterized by the remains of several peculiar terrestrial reptiles, namely, Iguanodon, Hylæosaurus, Pelorosaurus, Megalosaurus; Crocodilians and Chelonians; Enaliosaurians; Pterodactyles, &c.; Fishes of fluviatile and marine genera; Insects of several orders; fresh-water mollusks and crustaceans; conifers, cycads, ferns, &c.

Subdivisions:--

1. Weald-clay, with Sussex or Petworth marbles.

2. Tilgate-grit, and Hastings sands.

3. Ashburnham clays, shales, and grey limestones.

4. Purbeck beds; argillaceous and calcareous shales, and fresh-water limestones and marbles. Petrified forest, and layers of vegetable earth; with Cycads and Conifers.

Obs.--Clays and limestones, almost wholly composed of fresh-water snail-shells, and minute crustaceans, generally occupy the uppermost place in the series in Sussex; sands and sandstones, with shales, and lignite, prevail in the middle; while in the lowermost, argillaceous beds, with shelly marbles or limestones, again appear; and, buried beneath the whole, is a petrified pine-forest, with the trees still erect, and the vegetable mould undisturbed! The upper clay beds and marbles form the deep valleys or Wealds of Kent and Sussex, and the middle series constitutes the Forest-Ridge. The Purbeck strata are obscurely seen in some of the deepest valleys of eastern Sussex; they emerge on the Dorsetshire coast, form the Island or Peninsula whose name they bear, and surmount the northern brow of the Isle of Portland. On the southern coast of the Isle of Wight, the Wealden beds emerge from beneath the Greensand strata between Atherfield and Compton Bay on the western limit, and in Sandown Bay on the eastern; and their characteristic fossils are continually being washed up on the sea-shore.

The Jurassic or Oolitic Formation. (Wond. pp. 202, and 491). A marine formation of great extent and thickness, consisting of strata of limestone and clay, which abound in extinct species and genera of marine shells, Corals, Insects, Fishes, and terrestrial and marine Reptiles. Land plants of many peculiar types, and the remains of two genera of Mammalia.

Subdivisions:--

Upper Oolite of Portland, Wilts, Bucks, Berks, &c.

1. Portland Oolite. Limestone of an oolitic structure, abounding in ammonites, trigoniæ, &c. and other marine exuviæ. Green and ferruginous sands--layers of chert.

2. Kimmeridge clay. Blue clay, with septaria, and bands of sandy concretions--marine shells and other organic remains--ostrea deltoidea. Beds of lignite.

Middle Oolite of Oxford, Bucks, Yorkshire, &c.

1. Coral oolite, or Coral rag. Limestone composed of corals, with shells and echinites.

2. Oxford clay; with septaria and numerous fossils. Beds of calcareous grit, called Kelloway-rock swarming with organic remains.

Lower Oolite of Gloucestershire, Oxfordshire, and Northamptonshire.

1. Cornbrash--a coarse shelly limestone.

2. Forest marble; concretions of fissile arenaceous limestone--coarse shelly oolite--sand, grit, and blue clay.

3. Great oolite--calcareous oolitic limestone and freestone; reptiles, corals, &c., upper beds full of shells.

Stonesfield slate;--terrestrial plants, insects, reptiles, Mammalia.

4. Fullers earth beds;--marls and clays, with fuller's earth--sandy limestones and shells.

5. Inferior oolite--coarse limestone--conglomerated masses of terebratulæ and other shells--ferruginous sand, and concretionary blocks of sandy limestone, and shells.

Lower Oolite, of Brora in Scotland.

1. Shelly Limestones--alternation of sandstones, shales, and ironstone; land-plants.

2. Ferruginous limestone, with carbonized wood and shells.

3. Sandstone and shale; with two beds of coal.

Lower Oolite of the Yorkshire coast.

1. Cornbrash--a provincial term for a bluish grey rubbly limestone, with intervening layers of clay.

2. Sandstones and clays, with land-plants, thin beds of coal and shale--calcareous sandstone and shelly limestone.

3. Sandstone--often carbonaceous, with clays; coal-beds, and ironstone, with remains of vegetables.

4. Limestone; ferruginous and concretionary sands.

Obs.--The difference observable between the lower beds of the Oolite in the midland counties, and those of Yorkshire and Scotland, is a fact of considerable interest. The fluvio-marine accumulations of vegetable matter in the state of coal, with the remains of land-plants at Scarborough and Brora, together with the presence of insects, fresh-water crustaceans, mammalia, and terrestrial plants, in the Stonesfield slate, attest the existence of neighbouring land, and the action of rivers and currents.

The Lias. (Wond. p. 521) A series of clays, shales, and limestones, with marine shells, cephalopoda, crinoidea, and fishes in great abundance; reptiles, (particularly of two extinct genera, Plesiosaurus, and Ichthyosaurus,) in immense numbers. Drifted wood and land plants: coniferæ, cycadesæ &c.

Subdivisions:--

1. Upper Lias shale, full of saurian remains, belemnites, ammonites, &c. intercalated with the lowermost beds of the Oolite: nodules and beds of limestone.

2. Lias marlstone; calcareous, sandy, and ferruginous strata, very rich in terebratulæ and other marine shells.

3. Lower Lias clay and shale, abounding in gryphea incurva, and other marine shells; intercalations of sands and clays, with nodules of limestone.

4. Lias rock; a series of laminated limestones, with clay partings. Bone-bed, with numerous remains of fishes.

Obs.--The Lias is the grand depository of those tribes of marine reptiles, the Ichthyosauri and Plesiosauri, whose remarkable forms, structure, and state of preservation, have excited the attention even of the most incurious. The collection of these remains in the British Museum, principally formed by Mr. Hawkins, is unrivalled.[19]

[19] See "Petrifactions," p. 337-367.

The Trias; or New Red Sandstone Formation,[20] (Wond. p. 533). This group of rocks consists of variegated marls, sandstones, and conglomerates, frequently of a red colour, with marine shells, crinoideans, fishes, and reptiles; marine and terrestrial plants. This series contains extensive deposits of rock-salt, and brine-springs.

[20] Called by some geologists Poikilitic (variegated) group.

This formation comprises the Trias, or triple group, viz. the Keuper, Muschelkalk, and Upper Bunter Sandstein, of the German geologists.

Subdivisions:--

1. Variegated red, blue, and white marls, and shales, with gypsum and beds of rock-salt. (Marnes irisées of the French.)

2. Variegated red and white sandstones.

3. Conglomerates formed of the detritus of the older rocks.

4. Bed mottled sandstone, and marls. (Grès bigarré of the French.)

Obs.--To this formation belong the principal deposits in Leicestershire and other midland counties of England. Fossils are not generally abundant, but some localities yield highly interesting remains. The shelly limestone of Germany, called Muschelkalk, which contains the Lily Encrinite, &c. does not occur in England. Remains of Conifers allied to the Yew and Araucaria, are found near Coventry; and peculiar reptiles (Labyrinthodons) near Warwick.

Palæozoic Epochs.

The Permian Formation. (Wond. p. 533). The separation of the strata now termed Permian from the Triassic, with which they were formerly classed, was first proposed by Sir Roderick Murchison, and is based on the fact that the fossils hitherto discovered are entirely distinct from any that occur in the Trias and subsequent formations; it is, therefore, inferred, that after the deposition of the so-called Permian strata, a complete change took place in the faunas and floras of the lands and seas, and the Trias is at present regarded as the dawn of a new system of organic beings.

The strata comprised in this group are variegated blue and red marls and sandstones, like those of the Triassic; magnesian or dolomitic limestones; and conglomerates more or less coloured with peroxide of iron.

Subdivisions:--

1. Red and white marls.

2. Yellow magnesian limestones, and dolomitic conglomerates of Yorkshire and Durham.

3. Marl-slate in thin layers, containing reptiles and fishes. The Keuper schiefer or copper-schist of Mansfeld.

4. Marls and variegated sandstones, sands, and clays.

Obs.--This group includes the Lower Bunter, Zechstein, and Rothliegendes[21] of the German geologists. The Permian comprises all the deposits that intervene between the Triassic above, and the Carboniferous below; and it is believed that this formation contains but one type of animal and vegetable life.

[21] Signifying Red-dead-layer; it is a German mining term denoting that the copper of the upper bed has died out; this layer not being metalliferous.

The Carboniferous, or Coal Formation. (Wond. pp. 660-748). Sandstones, grits, shales, layers of ironstone, and clay, with immense beds of coal; fresh-water limestones sparingly; marine limestones abundantly.

Subdivisions:--

1. The Coal Measures.--Sandstones, shales, and grits, with numerous beds and seams of Coal; ironstone nodules. Land plants in profusion. Intercalations of bands of limestone with fresh-water bivalves and crustaceans in some districts; and with marine shells in others.

2. Millstone Grit.--Sandstones, shales, and quartzose conglomerates and grit, (provincially, Millstone-grit): with shales and thin seams of coal, and plants of the coal-measures in some localities. The conglomerates and grits have evidently resulted from the destruction of granitic rocks.

3. Carboniferous, or Mountain Limestone.--A series, nearly 1,000 feet in thickness, of limestones and flagstones, abounding in crinoideans, corals, and marine shells and crustaceans; with layers and nodules of chert. Ores of lead, zinc, copper, barytes; fluor spar, &c. Limestones, with innumerable shells of the genera Productus, Spirifer, Goniatites, Orthocera, Bellerophon, &c. Several varieties of black, bluish grey, and variegated marbles. Coal occurs in the mountain limestone of some parts of Russia.

Obs.--The strata comprised in the carboniferous (coal-hearing) system, consist of sandstones more or less felspathic, and of dark bituminous shales with innumerable ferns, and other vascular cryptogamiæ, and coniferæ, &c. The uppermost group is composed of numerous alternations of coal, clay, shale, ironstone, and sandstone; the middle, of sandstones, shales, clays, and quartzose conglomerates, generally of a dull red colour; and the lowermost, of crystalline limestones with occasional layers of chert, abounding in marine shells, corals, crinoidea, and other exuviæ. These lower limestones are the principal repositories of the lead ores of Derbyshire.

The Devonian or Old Red Formation. (Wond. pp. 204 and 751). Conglomerates, quartzose grits, sandstones, marls, and limestones; the prevailing colour is a dull red. Shells, corals, and ganoid fishes, of a very peculiar type. Reptiles, (Telerpeton; Batrachians? Chelonians?); the most ancient reptilian remains hitherto discovered. Ferns, Lepidodendrons, and other trees of the carboniferous flora; fluviatile plants with batrachian ova(?).

Subdivisions:--

1. Sandstone, quartzose conglomerates, and shale, with but few fossils.

2. Flagstones, marls, and concretionary limestones; provincially termed corn-stones; laminated reddish and greenish micaceous sandstones (prov. tilestones). Peculiar genera of fish; orthocerata, and many species of marine shells.

Obs.--The term Devonian, by which the series of strata comprehended in this formation is now generally distinguished by geologists, was first proposed by Sir R. Murchison, as being more precise than the name formerly applied to this group. In Scotland, where the formation is of vast extent, it was first characterized by its peculiar ganoid fishes (Pterichthys, Coccosteus, Cephalaspis), and will probably always there retain the original name of Old Red.[22] In Devonshire it is marked by the presence of shells of a character intermediate between those of the Silurian and Carboniferous systems.

The sandstones are in various states of induration, and when slaty, are employed for roofing. The red colour predominates in the marls, and is derived from peroxide of iron. The formation of these rocks has manifestly resulted from the waste of ancient slate rocks, the detritus of which is cemented together into coarse conglomerates. In South Devonshire (at Torquay, Babbicombe, &c.), beautiful coralline marbles occur in this formation.

[22] See the charming volume of Mr. Hugh Miller, entitled "The Old Red Sandstone, or New Walks in an Old Field."

The Silurian System. (Wond. p. 765). Marine limestones, sandstones, shales, and calcareous flagstones, characterized by peculiar types of corals, crinoideans, mollusks, and crustaceans, constitute this important and extensive system of rocks; the Grauwacké, or Transition series of the earlier geologists.

Subdivisions:--

UPPER SILURIAN.

1. Ludlow rocks;--slightly micaceous grey-coloured sandstones. Blue and grey argillaceous limestones. Dark-coloured shales and flagstones, with concretions of earthy limestone, containing marine shells, Orthocerata, Spirifers, and Trilobites. Fishes.

2. Wenlock, or Dudley limestone;--sub-crystalline blue and grey limestone, abounding in Trilobites, Crinoidea, Polyparia, Spirifers, Orthocerata, &c.

3. Wenlock shale;--dark grey argillaceous shale, with nodules of sandstone.

LOWER SILURIAN.

1. Caradoc sandstone;--shelly limestones, and finely laminated, slightly micaceous, greenish sandstones. Corals, Shells, Trilobites.

2. Llandeilo flags and limestones. Freestone, conglomerates, grits, and limestones. Dark-coloured flags. Beds of schist with abundance of Trilobites and shells. The lowermost beds are full of small bivalves, termed Lingulæ.

Obs.--The Silurian System, (so named by Sir R. Murchison, from the Silures, the ancient Britons who inhabited those parts of our island in which the geological relations of these strata were first recognised by him,) occupies the border counties of England and Wales, and spreads over a vast area of both North and South Wales, intervening between the Carboniferous series and the Cambrian or ancient slate-rocks of that country.[23] The strata are entirely of marine origin, and many of the beds (as the well-known Dudley or Wenlock limestone) are composed of shells, corals, crinoideans, and remains of that remarkable family of crustaceans termed Trilobites, cemented together by carbonate of lime. A few remains of Fishes occur: Reptiles are unknown. No vegetable relics, excepting Fuci, have been found in Britain below the Devonian or Old Red formation.[24]

[23] "The Silurian System, founded on Geological Researches in the Border Counties of England and Wales." In two parts, royal 4to., with map, sections, &c., by Sir R. I. Murchison, G.C. St.S. &c. In studying the beautiful map which accompanies the work, it must be borne in mind that ten years have elapsed since Sir R. Murchison abrogated the boundary line that separates the Cambrian and Silurian rocks in this chart, from the conviction that those deposits constitute but one natural system (see Wond. p. 80.3). For an account of the Silurian rocks of other countries, see "Geology of Russia," by the same Author. A summary of the characters of the Silurian System, by Sir R. Murchison, is given in Geolog. Journal, vol. viii. pp. 173-183.

[24] "The Silurian System" contains excellent figures of all the organic remains known at the period of its publication.

The Cambrian Formation. This term is applied to a largely developed series of unfossiliferous slate-rocks and conglomerates, many thousand yards in thickness.

Obs.--Certain beds of dark-coloured schists containing a few corals, fuci, and shells, are referred to the uppermost part of this formation by some eminent geologists, but it is more consonant to the established system of classification to regard these fossiliferous beds as the lowermost of the Silurian rocks. The fineness of grain, general aspect, hardness, and texture of these strata, are well known, from the general employment of slate for economical purposes. These rocks extend over a great part of Cumberland, Westmoreland, and Lancashire, reaching to elevations of 3,000 feet, and giving rise to the grand scenery of the Lakes, and of North Wales.

Hypogene Rocks. (Wond. p. 806.)

Non-fossiliferous.

Metamorphic (transformed) or stratified crystalline rocks.

Subdivisions.--

1. Mica-schist System. (Wond. p. 843.) Probably sedimentary rocks altered by high temperature. Mica-slate, Quartz-rock, Crystalline limestone, Hornblende schist, &c.

2. Gneiss System. Layers of Gneiss, Sienite and Quartz-rock, alternating with Clay-slate, Mica-schist, &c.

Plutonic Rocks; unstratified crystalline masses.

Granitic System. (Wond. p. 844.) Granite--a rock composed of mica, quartz, and felspar; Porphyry; Serpentine; Trap. These rocks occur in amorphous or shapeless masses, and in dykes and veins.

Obs.--No fossils have been detected in these rocks: but the intense igneous action which the masses appear to have undergone, may have obliterated all evidence of animal and vegetable structures, should any have been present, as well as the lines of stratification. By the aid of the microscope, we may yet perhaps solve the mystery which shrouds the origin of these rocks, and the student may take up the investigation with the certainty of obtaining much valuable information, even should the search for organic structures prove abortive. It is not, however, improbable that the siliceous frustules of diatomaceæ may have escaped destruction, and remain to reward the researches of some skillful and patient observer.

Volcanic Rocks. (Wond. p. 815.)

The products of subterranean fire or heat, erupted from profound depths through fissures in the Earth's crust, whether in ancient or modern times.

Subdivisions.--

1. Trap, Basalt, Toadstone, Volcanic-tuff; the erupted materials of ancient extinct volcanoes.

2. Lavas, Scoriæ, Pumice, Ashes; ejected by modern volcanoes.

Obs.--These igneous products are of all ages, and they traverse alike the hypogene rocks and the older and newer sedimentary deposits. Their characters, and the effects they have produced, are considered in the work to which reference is made.

* * * * *

By a reference to the geological map of England (Wond. pl. i. vol. i.), it will be seen, that the several formations appear on the surface in a somewhat chronological order, as we pass from the eastern or south-eastern part of the Island to the west or north-west. Thus the principal Tertiary deposits are situated in the eastern and south-eastern parts; and proceeding towards the north-west, we traverse successively the Secondary--the Chalk, Oolite, Lias and Trias; then the Palæozoic--Permian, Carboniferous, and Devonian; next the Silurian and Cambrian; and at length metamorphic and primary rocks appear. It is this distribution of the strata of the respective formations that has determined the characters of the physical geography of England. The Alpine or mountainous districts, which extend north and south along the western portion of England and Wales, from Cornwall to Cumberland, are formed by the elevated masses of the Silurian, Cambrian, and Metamorphic rocks. These are succeeded by a band of the Carboniferous and Triassic deposits, with a few intrusions of metamorphic and plutonic rocks, that stretches from the coast of Devonshire, through the midland counties, by Leicestershire and Derbyshire, to Newcastle. On the south-east of this tract, the Oolite and Cretaceous formations, chiefly made up of argillaceous and calcareous strata, constitute a diversified agricultural district, extending from the southern shores of Hants and Dorset to the coast of Yorkshire. The Wealden occupies the country lying between the Chalk Downs of Sussex, Hants, Surrey, and Kent. The Tertiary deposits lie in basins or depressions of the upper cretaceous rocks in the south-eastern and eastern maritime districts, and on an extensive area of these beds stands the metropolis of England; lastly, irregular accumulations of Drift, containing mammalian remains in some localities, are spread over the surface of the ancient formations, and form the immediate subsoil of the most fertile regions.

III. ON THE NATURE OF FOSSILS, OR ORGANIC REMAINS

Fossils; Petrifactions.--It is very generally the case, that persons who are not conversant with the nature of organic remains, suppose that all fossils are petrifactions; and unless a specimen has the aspect and hardness of stone, they regard it as of modern origin, and devoid of interest. Hence they are surprised to find among the choicest treasures in the cabinet of the geologist, shells and corals as perfect in form, as if recently collected from the sea-shore; bones as little changed, as if they had been interred but for a short period; and teeth possessing their sharp edges and enamel unimpaired. In my early researches I fell into this error, and threw away many beautiful shells that were associated with casts of ammonites in the marl at Hamsey, supposing, from their perfect state, that they had been accidentally imbedded, and were not genuine fossils. But the state of preservation, and the degree of change which an organic body has undergone in the mineral kingdom, have no necessary relation to its antiquity. The shells in some of the ancient secondary strata are frequently as little changed as those in modern tertiary deposits. I have collected from the lowermost clays of the Wealden, fresh-water shells with traces of the epidermis, and the ligament by which the valves were held together, perfect; and bones of reptiles from the strata of Tilgate Forest, as light and porous as those of the bears and hyenas, from the Caverns of Germany. On the other hand, fossil remains from the newest tertiary formations are often completely petrified, that is, permeated by, or transmuted into, stone.

The words fossil and petrifaction are so commonly used as synonymous terms, even by educated persons, that it is necessary to define the sense in which they are employed in these volumes.

Fossils are the durable parts of animal and vegetable structures imbedded in rocks and strata by natural causes at a remote period; thus wood in a state of lignite, bog-wood, and coal, or of siliceous or calcareous stone, is fossil wood; and bones or shells, whether in an earthy and decaying state, or permeated by calc-spar, flint, or iron, and converted into a hard mineral substance, are alike fossil bones or shells.

Petrifactions are the remains of animals and vegetables in which the original structure is converted into stone, or, in other words, is petrified; such are the silicified stems of trees from Antigua, and Germany, and the calcified bones and shells in the Oolitic and Wealden limestones. Such petrifactions may be correctly termed fossil plants, bones, or shells; but similar organic remains, though of equal antiquity, which have not undergone such changes, are not petrifactions in the proper meaning of that term.

The process by which petrifaction is effected is still involved in obscurity; mineral solutions have permeated the original tissues, and the organic molecules have been replaced by mineral molecules, but how this transmutation is produced is not understood. Mr. Dana's observations and Mr. Jeffery's experiments have, however, thrown much light on the process of silicification.[25]

[25] See Wond. p. 100.

Incrustations.--Another prevalent error is that of considering Incrustations to be fossils or petrifactions; a mistake which is sanctioned by the custom of calling waters that are charged with calcareous earth (lime), and deposit it in considerable quantity, petrifying springs; as those of Matlock, and other places in Derbyshire. (Wond. p. 76.) But incrustations are not petrifactions; stems and branches of trees, skulls, bones, shells, &c., are simply invested with a calcareous coating or crust, which is generally porous and friable, but often crystalline and compact. The inclosed bodies are not permeated by the stony matter; if the mass be broken, or the incrustation removed, we find the twig, or stem, either dry and shrivelled, as in the specimens, figs. 2, 3, 4, Plate III.; or tubular cavities are left by the decay and removal of the vegetable structure, as in fig. 10, Plate III.

But although incrustations be not petrifactions, natural specimens, (not the so-called petrified nests and twigs, in which the bad taste of the guardians of the Derbyshire springs is embodied, and dispersed all over England,) are objects of considerable interest, as illustrative of a process, by which important changes are effected in the mineral kingdom. Thus springs as clear and sparkling as poet ever feigned or sung, may transform beds of loose sand and gravel into rock, and porous stone into solid marble, and cover extensive tracts of country with layers of concretionary and crystalline limestone. This process is effected in the following manner. Most fresh water holds in solution a certain proportion of carbonate of lime; and changes of temperature, as well as other causes, will occasion this calcareous earth to be in part or wholly precipitated. The fur, as it is called, that lines a kettle or boiler which has been long in use, affords a familiar illustration of this fact. At the temperature of 60° lime is soluble in 700 times its weight of water; and if to the solution a small portion of carbonic acid be added, a carbonate of lime is formed, which is thrown down in an insoluble state. But if the carbonic acid be in such quantity as to supersaturate the lime, it is again rendered soluble in water: it is thus that carbonate of lime, held in solution by an excess of carbonic acid, not in actual combination with the lime, but contained in the water, and acting as a menstruum, is commonly found in all waters. An absorption of carbonic acid, or a loss of that portion which exists in excess, will therefore occasion the lime to be set free, and precipitated on the foreign bodies in the water, as stones, twigs, leaves, &c.

The substance thus deposited is termed tufa, or travertine;[26] and in some parts of Italy, and of our own Island, it constitutes beds of stone of great extent, in which bones, shells, and the impressions of leaves and stems, are preserved. The stalactites and stalagmites of caverns have a similar origin; many of these caves are of incalculable antiquity, and beneath their stalagmitic floors, the bones and teeth of extinct carnivorous animals are found in vast quantities.

[26] Travertine, so called from the river Tibur, whose waters are loaded with calcareous earth--Tiburtina, Ital. travertina.

Silicification, or petrifaction by Silex or Flint.--Silex, or the earth of flint, is held in solution in large proportions, in certain thermal or boiling springs, which, on cooling, deposit the siliceous matter (in the same manner as the travertine is precipitated from incrusting streams) on foreign substances, and produce exquisite chalcedonic infiltrations of mosses, &c. But this operation is now only known to be in activity in the immediate neighbourhood of foci of volcanic action, as in the celebrated Geysers of Iceland (Wond. p. 95), and the boiling springs of the volcano of Tongariro, in New Zealand (98). We have everywhere evidence that in former periods, the petrifaction, as well as the incrustation of organic bodies by silex, was carried on to an immense extent; and, doubtless, far beneath the surface, the same operation is at the present moment in constant progress, and effecting as important changes in the consolidation of loose materials, as in the earlier geological epochs.

The various states in which silex occurs have depended on its fluidity; in quartz crystals the solution appears to have been complete; in agate and chalcedony it was in a gelatinous state, assuming a spheroidal or orbicular disposition, according to the motion given to its particles. Its condition appears also to have been modified by the influence of organic matter. In some polished slices of siliceous nodules the transition from flint to agate, chalcedony, and crystallized quartz, is beautifully shown. The curious fact, that the cavities of echinites in chalk are almost invariably filled with flint, while their crustaceous cases are changed into calc-spar, is probably, in many instances, to be attributed to the animal matter having undergone silicification; for the soft gelatinous parts are those which appear to have been most susceptible of this transmutation. In some specimens, the oyster is changed into flint, while the shell is converted into crystallized carbonate of lime. In a Trigonia from Tisbury, formerly in the cabinet of the late Miss Benett, of Norton House, near Warminster, the body of the mollusk was completely metamorphosed into a pure chalcedony, the branchiæ or gills being as clearly defined as when the animal was recent. In specimens of wood from Australia (presented to the British Museum by Sir Thomas Mitchell), which are thoroughly permeated by silex, there are on the external surface some spots of chalcedony that have apparently originated from the exudation of the liquid silex from the interior in viscid globules filled with air, which burst, and then collapsed, and became solidified in their present form.

In silicified wood the permeation of the vegetable tissues by the mineral matter, appears to have been effected by solutions of silex of a high temperature. In some examples the mineralization is simply a replacement: the original substance has been removed atom by atom, and the silex substituted in its place.

One of the most eminent naturalists and chemists of the United States, Mr. Dana,[27] suggests that the reason why silica is so common a material in the constitution of fossil wood and shells, as well as in pseudo-morphic crystals,[28] is the ready solution of silex in water at a high temperature (a fact affirmed by Bergman[29]) under great pressure, whenever an alkali is present, as is seen at the present time in many volcanic regions, and its deposition again when the water cools. A mere heated aqueous solution of silica, under high pressure, is sufficient to explain the phenomenon of the silicification of organic structures. Mr. Dana states that a crystal of calc-spar in such a fluid being exposed to solution, from the action of the heated water alone, the silica deposits itself gradually on a reduction of temperature, and takes the place of the lime, atom by atom, as soon as set free. Every silicified fossil is an example of this pseudo-morphism; but there seems to be no union of the silica with the lime, for silicate of lime is of rare occurrence.[30]

[27] American Journal of Science for January 1845.

[28] Pseudo-morphic crystals are crystals moulded in the cavities left by other crystals which they have replaced. See Dr. Blum on Pseudo-morphous minerals.

[29] Bergman first determined the solubility of silex in simple water, aided by heat, and demonstrated its existence in the Geysers and other boiling springs of Iceland.--Parkinson, Org. Rem. vol. i. p. 324.

[30] See my "Notes on a Microscopical Examination of Chalk and Flint," Annals of Natural History, August 1845.

* * * * *

I proceed to consider the various states in which the remains of animals and plants are preserved in the mineral kingdom, and shall occasionally offer suggestions for collecting and preparing specimens; but particular instructions on this head will be given in the sequel, when the different kinds of fossils are respectively considered.

[Sidenote: FOSSIL ANIMAL REMAINS.]

Animal Remains.--Of the higher orders of animals, the more durable portions of the skeleton, as the bones and teeth, are almost the only parts that occur in a fossil state; except in some remarkable instances, in which entire carcasses of extinct species of Elephant, and of Rhinoceros, have been found imbedded in solid ice, and frozen gravel. (Wond. p. 152.) The countries of arctic regions are now the only localities in which such phenomena are likely to be met with; it appears, however, that in some remote period, the bodies of large mammalia were transported by icebergs into temperate regions, where the ice melted, and the animals either sunk to the bottom of the sea, or were drifted into estuaries, or stranded on the shore: the soft parts then decomposed, and the skeletons and detached bones were left imbedded in the silt, sand, or shingle.

In this manner alone can be explained the occurrence of bones and teeth of the mammoth, rhinoceros, hippopotamus, &c. so common in the alluvial or drifted deposits of this country; for these relics, though extremely friable, and buried in shingle, boulders, and other transported materials, are not water-worn, but in numerous instances remain as sharp and perfect as when recent. In the ancient shingle of Brighton cliffs (Wond. p. 114), I have found bones and teeth of horse, deer, ox, whale, &c. impacted with quartz and granite pebbles and boulders; the bones, though crumbling to pieces if not very carefully removed, being entire, and the whole mass held together by calcareous spar, deposited by water that had, during the lapse of ages, percolated through the chalk-rubble above.

Fossil bones are found in four different states: 1. With their animal matter, as in the bones of the Mastodons from Big-bone Lick, Kentucky. 2. With the animal matter removed. 3. With the earthy matter partly removed, 4. With the animal matter carbonized, or converted into bitumen; this change is common in the blue Lias clay; the bones retain their usual quantity of phosphate of lime, but the animal matter is converted into carbon. This alteration appears to have taken place unconnected with a high temperature, and to have been a spontaneous change in a moist situation, to which air had no access.[31]

[31] Mr. Smee, London Med. Gazette, November 1840.

Another, and very remarkable condition, is that in which the phosphate of lime has been removed by the infiltration of water charged with sulphuric or carbonic acid, and the gelatin converted into leather by tannin; as is the case with bones and teeth of deer, horses, &c. obtained from a submerged forest of oak, larch, &c. near Ferry-bridge, in Yorkshire; of which there are many instructive specimens in the York Museum.[32]

[32] Communicated by Professor John Phillips.

The cancellated structure (that is, the little cells or pores) of the long-bones of mammalia, found in caverns in England and Germany, and in the breccia of Gibraltar, and the conglomerates of Ava and the Sub-Himalaya mountains, &c., are often filled with crystallized carbonate of lime. In the Wealden deposits the osseous carapaces and plastrons of Turtles, and the bones and teeth of Crocodiles, Lizards, &c., are almost without exception heavy, and of various shades of brown or umber, from the infiltration of solutions of carbonates and oxides of iron.

In some instances, bones of a jet black are imbedded in the white calciferous grit; the phosphoric acid in the original organism having combined with iron and produced a deep blue or black phosphate of that mineral, and left the surrounding stone uncoloured.

Petrifaction by the infiltration of calcareous solutions is equally common; and the medullary cavities of the bones are frequently lined or filled with white calc-spar; brilliant pyrites also enters into the composition of these fossils, frosting over with a golden metallic deposit the cavities and fissures.

[Sidenote: FOSSIL BONES.]

The permeation of the teeth by mineral matter, produces beautiful examples of the tissues of those organs; the dentine is often stained throughout with a rich sienna tint, and sections viewed under the microscope by transmitted light, reveal the character and distribution of the calcigerous tubes more clearly even than in recent specimens.

It is extremely rare that osseous structures are found petrified by flint; among the many thousands of bones which I have extracted from the rocks, or have seen in collections, I know but of one instance of a silicified vertebra, that of a Mosasaurus, from a chalk-pit near Brighton; and a few bones and scales of fishes. But notwithstanding the weight and apparent solidity imparted by these modes of mineralization, the substance is generally rendered extremely brittle, so that the development of the bones from the stone in which they are imbedded, and the removal of the hard ferrugino-calcareous crust investing them, is no easy task, but requires much tact, experience, and patience, to execute successfully.

Hints for collecting fossil bones.--The light, friable, porous bones, require great care in their removal from the deposit in which they are imbedded, whether it be clay, consolidated shingle, or limestone; if of considerable size, they will almost invariably break to pieces, and many examples will not admit of repair. It is therefore always desirable, before attempting to extract a large bone, to make a sketch of it; its form will thus be known, should it be destroyed; and if it crack into fragments that will admit of reunion, the drawing will be a valuable guide for the replacement of the separated parts. If only a few pieces remain, those which show any portion of the terminations, or joints, should be preserved, as they afford the most precise and important characters. The faithful record even of an imperfect and unknown fossil is not without value; and as the antiquary carefully preserves shreds of ancient manuscripts, in the hope that other documents may one day come to light, and enable him to interpret these now unintelligible records; so the geologist should treasure up every fragment of an undetermined organic remain, for the time may arrive, as I have often experienced, when specimens will be discovered that may illustrate its nature, and prove it to be of considerable interest.

The broken porous bones may be easily repaired by a hot weak solution of glue; and when the joinings are set, the bone should be saturated with thin glue, well brushed in, and the surface be sponged clean with very hot water before the cement is congealed. When dry, the specimens will be found to possess considerable firmness and durability.[33] By this process the tusks of mammoths and elephants may be restored, however much crushed; time, patience, and a little dexterity, only are required, to convert a heap of mere fragments into a valuable relic of the ancient world.

[33] A liquid, called "Neuber's liquid glue," is an excellent cement for this purpose: it is sold at No. 54, New Oxford Street, London.

When the bones are tolerably perfect, but dry and friable from the loss of their animal oil, they may be made durable by saturating them with drying oil, and exposing them to a considerable degree of heat; in this manner the magnificent skeletons of the sloth tribe, the Megatherium, and Mylodon, in the Hunterian Museum, were prepared. When a bone appears as if cracked into numerous pieces before its removal, but still preserves its form, the only method by which it can be successfully extracted, is by spreading over it a thick layer of plaster of Paris, which should be used of the consistence of cream; when it sets, (which, if the plaster be recently prepared, will be in the course of a few minutes,) the specimen may be carefully extricated, and the plaster removed or not, according to the nature of the fossil, and the parts to be displayed. The bones of the large reptiles which occur in the Wealden and Oolite, may be restored in the same manner. These remains are generally very brittle, and when imbedded in hard grit cannot be extracted whole: they will often fall to pieces on the slightest blow of the hammer or chisel. When of moderate size, it is best not to attempt their removal from the stone, but to trim the block into a convenient shape, and carefully chisel away the surrounding part, so as to expose the essential characters of the bone. In all cases this is an excellent method where practicable, for such specimens have a double interest; they are at once illustrative examples of the fossil, and of the rock in which it was deposited.

But many specimens will not admit of this method; and with large ones it is inconvenient and undesirable, except where bones lie in juxtaposition. The large examples in Tilgate grit, (figured in the Fossils of Tilgate Forest,) were all extracted piecemeal from the rock: and most of the gigantic bones of the Iguanodon, &c. now in the British Museum, were originally in many hundred pieces, and were cemented together with glue in the manner above described; I have found no other method so convenient and effective.

When a bone is too imperfect to be united as a whole, it may be imbedded in Roman cement, or plaster of Paris, which when dry may be coloured of the prevailing tint of the rock. For large heavy specimens, the cement is preferable; it is of easy application, and the fissures and cracks of the bones may be filled up with it, taking care first to cover the parts with thin hot glue, or the cement, when it dries, will shrink and fall out. A thin coating of mastic varnish will restore the colour, and by excluding the air, tend to preserve the specimens.

The teeth have generally undergone the same changes as the bones with which they are associated. The teeth of elephants or mammoths that are imbedded in loose calcareous earth, like the loam and chalk-rubble of Brighton cliffs, and of Walton in Essex, are friable, and apt to split and separate in the direction of the vertical plates of dentine and bone: the pieces should be glued together, and when set, the tooth be thoroughly saturated with thin glue, used very hot, and the superfluous cement removed with a sponge wrung out as dry as possible from boiling water. If there be any portion of the jaw attached to the teeth, it must be carefully preserved; and search should be made for fragments of the articulations, or parts of the joints and sockets.

In argillaceous strata, as the Lias-shale, London Clay, &c., the fossils are frequently saturated with brilliant pyrites, or sulphuret of iron; a mineral which decomposes upon exposure to the atmosphere, and occasions the destruction of the specimens. The fossils of the Isle of Sheppey are peculiarly obnoxious to this change.

[Sidenote: FOSSIL ANIMAL REMAINS.]

The remains of vertebrated animals in the Lias, very often occur as skeletons more or less perfect, the entire configuration of the original being preserved in many instances (Bd. pl. 7. Petrifactions, p. 340). But the deposit in which they lie is generally laminated, and the shale flakes off without great care; much time, labour, and practice are therefore required, to obtain specimens of any considerable size. To the late Miss Mary Anning, of Lyme Regis, the merit is due, of having first accomplished this difficult task; Mr. Hawkins has subsequently carried the art to perfection, as may be seen in the marvellous examples of Ichthyosauri and Plesiosauri, in the British Museum.[34]

[34] Petrifactions, Room IV. chap. iv. pp. 341, 376.

The small specimens, such as the detached paddles, groups of vertebræ and ribs, &c., that are likely to come under the collector's notice in his personal researches, are not difficult of preservation. Mr. Hawkins employed a strong watery solution of gum arabic as the cement, and plaster of Paris as the ground, using shallow wooden trays of well-seasoned wood, in which the specimens were permanently imbedded: the bones, scales, &c. were then varnished with a solution of mastic, and the ground coloured bluish grey, to imitate the Lias. I have had considerable practice in the dissection of skeletons imbedded in Lias, and having found the method previously described answer every purpose, have not employed that recommended by Mr. Hawkins.

The scales of reptiles and fishes, either in connected masses or detached, are frequently met with in great perfection, and sometimes associated with the teeth and bones. In the Lias, even the remains of the skin and integuments (Bd. pl. 10) have been discovered. Whenever any part of a skeleton is found lying in shale or stone, the surrounding block should therefore be carefully examined, to ascertain if there be traces of the skin or integuments, before any part is removed by the chisel. The specimen of an Ichthyosaurian paddle, figured in the second volume of this work, affords a good illustration of the propriety of this caution. Around the bones are seen the carbonized remains of the cartilaginous fringe that supported the integuments, and thus the perfect form of the paddle has been ascertained; had the surrounding stone been chiselled away, the most important characters would have been obliterated, as probably they have been in numerous instances.

Nodular masses of indurated clay containing fishes, are often broken with difficulty in such a manner as will expose the enclosed fossil, for the nodule generally splits in various directions, and the specimen is irreparably mutilated or defaced. My friend Sir Woodbine Parish informs me that by subjecting such nodules to a high temperature--but not to a red heat--and then plunging them in cold water, they may when dry, by a properly directed blow of a hammer, be readily fractured in a direction parallel with the plane of the imbedded fossil, and the fish be laid bare in the most favourable position.

The scales of fishes, and the integuments of marine reptiles, are not the only vestiges of the dermal coverings of vertebrated animals that are preserved by mineralization. Traces of the wing-integument of flying reptiles, and of the feathers of birds, are sometimes manifest: and even when every atom of the original structure has perished, the impression may remain, and afford satisfactory results. The footmarks of unknown animals are often preserved in the rocks, and the imprints of the feet of several species of bipeds, presumed to be birds of colossal size, in tracks as distinct as if but recently made, have been discovered in the New Red sandstone of North America; in the section on fossil birds, this highly interesting subject will be fully explained.

The student, even from this brief review, will perceive how many valuable facts may be unnoticed, and irretrievably lost, unless attention be paid to the various circumstances under which fossil remains are presented to his notice.

Of the invertebrated orders, the most durable, and consequently the most numerous relics, are shells and corals. The integuments of the eyes, antennæ, and wings of Insects occur; and the shelly coverings of Crustaceans are not uncommon; those of the Echinoderms, the Star-fishes, and of the Crinoidea or Lily-animals, are very abundant in certain deposits. Instructions for the collection and arrangement of these fossils will be given in the chapters in which they are severally described.

Part II

⎼⎼⎼⎼⎼◆⎼⎼⎼⎼⎼

IV. FOSSIL BOTANY

Fossil Vegetables.--The remains of the vegetable kingdom are presented to the notice of the geologist in various conditions; in some instances these relics are but little changed in their aspect, as, for example, in the recent accumulations of mud and silt, at the bottoms of lakes and rivers, and in morasses, and peat-bogs. In tufaceous incrustations, the imprints of wood, and of leaves and stems, are often sharply defined on the solid masses of concretionary and crystalline limestone.

In the ancient deposits, vegetables are found in two different states. In the one their substance is completely permeated by mineral matter; it may be calcareous (lime), siliceous (flint), ferruginous (iron), or pyritous (sulphuret of iron); and yet both the external characters, and the internal structure, may be preserved. Such are the fossil trees of the Isle of Portland, fragments of which so closely resemble decayed wood, as to deceive the casual observer, until by close examination of their texture and substance he finds that they possess the weight and hardness of stone. In the silicified wood which abounds in many of the tertiary strata, the most delicate tissues of the original are preserved, and by microscopical examination (see Pl. V.) may be displayed in a distinct and beautiful manner. In calcareous fossil wood the structure is also retained; and in many limestones, leaves and seed-vessels are well preserved.

The ligneous coverings, or the husks and shells, of nuciferous fruits, and the cones or strobili of Firs and Pines, are frequently met with in an excellent state of preservation; in some rare instances indications of flowers have been observed (Lign. 67). The parts of fructification in some of the fern tribe (Lign. 25 and 27), occur in coal-shale, and in the grit of Tilgate Forest (Wond. p. 394): the pollen, and the resinous secretions of pines and firs, have been discovered in tertiary marls, and in the Greensand. The well-known substance. Amber, so much in request for ornaments, is unquestionably of vegetable origin; it has been found impacted in the trunks of its parent trees (Wond. p. 242). The fossil resin discovered in the London clay, at Highgate and the Isle of Sheppey, is doubtless referable to the coniferæ found in that deposit.

In the Clathrariæ of Tilgate Forest, indications of a resinous secretion have been detected.

The Diamond, which is pure charcoal, is probably a vegetable secretion, that has acquired a crystalline structure by electro-chemical forces. It has been converted into Coke and Graphite by the action of intense heat; and the electrical properties of the substance were changed, the Diamond being an insulator, and the Coke, a conductor of electricity. (Wond. p. 706.)

When the microscope is more extensively employed in investigations of this kind, it is probable that the siliceous spines and stars which begem the foliage of many plants (as the Deutzia, Lithospermum officinale, &c), will be discovered in a fossil state, for they are as indestructible as the frustules of Diatomaceæ, and the spicules of sponges which are so common in flint and chalcedony.

[Sidenote: FOSSIL VEGETABLES.]

But vegetables occur not only as petrified stems, leaves. and fruits, associated with other remains in the strata, but also in beds of great thickness and extent, consisting wholly of plants transmuted, by that peculiar process which vegetable matter undergoes when excluded from atmospheric influence, and under great pressure, into Lignite, and Coal. And there are intermediate stages of this process, in which the form and structure of the trees and plants are apparent; and a gradual transition may be traced, from the peat-wood and submerged forests of modern epochs, in which leaves, fruits, and trunks of indigenous species are preserved, to those ancient accumulations of carbonaceous matter, whose vegetable origin the eye of science can alone detect.

For the collection and preservation of fossil vegetables, with the exception of those which are permeated with. pyrites (as those of the Isle of Sheppey, &c.), but few instructions are required. The silicified and calcareous stems are generally easy of extraction, even when imbedded in hard stone, and if broken can be repaired with glue. When the stems bear the imprints of leaf-stalks (as in Lign. 31 and 54), the surrounding stone should be carefully examined, with the view of detecting impressions, or other indications of the foliage. Delicate leaves in clay, or shale, must not be washed; a thin coat of mastic varnish, or of gum-water, applied with a camel-hair pencil, will preserve them, and render them more distinct. When a leaf, fruit, seed-vessel, or other fragile object is attached to clay or friable sandstone, it is advisable to glue the specimen to a piece of thin wood or pasteboard, of suitable proportions.

The Sheppey fruits and other fossils permeated with iron pyrites, generally decompose after a few months' exposure to the air. The fruits, especially, are liable to decomposition; Mr. Bowerbank keeps his specimens in bottles of water; a solution of isinglass in spirits of wine is the best varnish to preserve such fossils, without obscuring their character and injuring their appearance: but even this method is often unavailing. The pyritified fir-cones of the Wealden decompose in like manner: I have had the misfortune to lose several unique and most instructive specimens from this cause; boiling them in linseed oil preserves them, but greatly impairs their appearance.

* * * * *

ON THE INVESTIGATION OF THE FOSSIL REMAINS OF VEGETABLES.

Vegetable Organization.--As fragments of the stems, trunks, and branches, are very often the only vestiges of fossil plants, a knowledge of the characters by which the principal divisions of the vegetable kingdom may be distinguished by their internal structure, is indispensable to the successful investigation of the Flora of the ancient world. Although I have treated of this subject in the Wonders of Geology, (Wond. p. 694,) it will here be necessary to present the student with more ample details. The excellent introductory botanical works of Dr. Lindley, and Professor Henslow, convey full information on this, and every other department of the science, and should be consulted by those who intend to make this branch of Geology their particular study. For the general reader, and amateur collector, the following brief notice of a few obvious essential characters of vegetable organization, may perhaps afford sufficient information, to enable them to understand the principles on which the successful investigation of the nature and affinities of fossil plants must be conducted.

[Sidenote: STRUCTURE OF VEGETABLES.]

Every plant is essentially an aggregation of cells;[35] and the most simple forms of vegetation consist of a congeries of cells (cellular tissue) of the same kind, and have no visible fructification; such are the sea-weeds (algæ, conferæ, &c.), mosses, and lichens. In the more complex tribes the cells become variously modified, are elongated into tubes or vessels (vascular tissue), some of which possess a spiral structure, and others have their sides studded with little glands. The vascular tissue consists of two kinds of vessels. 1. The spiral vessels or tracheæ: these are membraneous tubes, with conical extremities, having within a coil of elastic fibre spirally twisted, and capable of being unrolled (Lign. 1, b.). 2. The ducts; which are a modification of the structure of the spiral vessel; their extremities are rounded or conical, and their sides marked with transverse lines, rings, or bars. Their functions appear to be different from those of the spiral vessels, and they are found in situations where the latter never occur.

[35] "A cell in botanical language, means a little bag composed of membrane, and containing a living substance capable of spontaneous growth by multiplication, or division of its parts. Of such little bodies, millions of which may be contained within the space of a cubic inch, all the soft parts of vegetables are composed; in sea-weeds they are often of large size."--Dr. Harvey's Sea-side Book, with which the reader is doubtless familiar.

The organization of the stem in the whole class of flowering plants, possesses characters so evident, as to afford the most important aid in the investigation of their fossil remains. Without dwelling on minor modifications, they are separable into two divisions, namely, the Endogenous (signifying to grow from within), and the Exogenous (to grow from without). Both possess vascular tissue, but so differently arranged in the two classes, as to constitute distinctive characters which are seldom obliterated, although what was once a flexible stem, is now a mass of flint.

Endogenous Stems.--As the seeds of the plants belonging to this division have but one cotyledon, or seed-lobe, as the Lily, they are also termed monocotyledonous; the reader therefore must remember that these terms are synonymous. These stems consist of an uniform mass of cellular tissue, in which bundles of vascular or woody fibre are imbedded; a transverse section presents a surface dotted over with spots, produced by the division of these groups of vessels, pretty uniformly distributed, but more densely arranged towards the circumference (Lign. 1, fig. 4). A slice of cane affords an illustration of this structure.

The increase of these stems is effected by the formation of new cells and bundles of vessels in the central axis, which force their way among the old tissue, and occasion the condensation of the latter towards the outer edge. These plants have neither pith, concentric circles of woody fibre, nor true bark; negative characters of the highest importance in the determination of fossil stems.

Exogenous Stems.--The seeds have two cotyledons, or seed-lobes, as in the Bean, hence the plants of this class are also called dicotyledonous. In these stems the cellular tissue forms a central column, or pith (_Lign. 1, fig. 2, a.), and an external band, or cylinder, called the bark (fig. 2, b.); the two being connected by thin vertical plates, termed medullary rays, which are also formed of cells (fig. 2, c, c.); the diagram, Lign. 1, exhibits this arrangement. The interval between the pith and the bark, and the interspaces of the vertical radiating plates (fig. 2, d.), are filled up by woody fibre or vascular tissue, consisting of spiral and other vessels. The ligneous structure of exogenous stems consists, therefore, of a cylinder formed of wedge-shaped processes, that extend between the medullary rays to the pith, and is surrounded by the bark; a new zone of woody fibre is added annually between the bark and the former cylinder, and from this mode of increase the term exogenous is derived: a transverse section of a branch of oak or ash will show this structure. The rings, or concentric circles, are the annual zones of wood; the fine lines radiating from the centre, or pith, to the circumference, or bark, are the medullary rays (Lign. 1, fig. 2, c: see also Plate V. fig. 4).

The organization above described, will be found more or less manifest in fossil wood, stems, and branches. The monocotyledonous structure is beautifully displayed in the silicified stems of palms from Antigua (Plate V. fig. 1, 1^a.): and the dicotyledonous, in petrified trees from Egypt. The pith, medullary rays, vascular tissue, and circles of growth, are preserved in the siliceous and calcareous wood found in many parts of England.

[Sidenote: STRUCTURE OF CONIFERÆ.]

Structure of Coniferæ (cone-bearing).--The remains of a numerous family of dicotyledonous trees, termed Coniferæ, as the pine, fir, larch, &c., are so abundant in the stratified rocks, that it is necessary to describe in more detail the peculiarity of structure by which their stems and branches may be recognised. The most delicate woody tissue, as we have above stated, consists of elongated cells or tubes, of two kinds: in the one, the membrane of which they are composed is smooth: in the other, the walls of the tubes are covered by little oval or circular bodies called glands (Lign. 1, fig. 1, c.). A branch of larch or pine, split longitudinally, and viewed by a powerful lens, will exhibit the appearance here described. This glandular structure is so constantly and largely developed in the coniferæ, that although it is also possessed by other aromatic trees, we shall rarely err in referring fossil wood in which this organization is apparent, to this family of vegetables (see Plate V. figs. 2, 3). These glands in the pines and firs, are supposed to be the cells which secrete a colourless volatile oil, that exudes in the state of turpentine.

From this general account of the vegetable structures that may be expected to occur in the mineral kingdom, the student will in some measure be prepared for the investigation of fossil trees and plants; but for the guidance of those who are wholly unacquainted with the principles on which the Natural System of Botany adopted in this work, is founded, I am induced to present the following concise view of the principal divisions of the vegetable kingdom, though it involves some repetition.

[Sidenote: BOTANICAL PRINCIPLES.]

The following summary is given nearly in Dr. Lindley's own language:--

Botanical Principles.--One of the first things that strikes an inquirer into the structure of plants, is the fact, that while all species are capable of propagating their race, the mode in which this function is effected is essentially different in different cases. In most tribes of plants, flowers are produced, and these are succeeded by fruit, containing seed, which is shed, or scattered abroad, and grows into new individuals. But in certain families (the Cryptogamia), as Ferns, Mosses, Mushrooms, and the like, neither flowers, nor seeds properly so called, have been detected; but propagation is effected by the dispersion of grains or spores, which are usually generated in the substance of the plant, and seem to have but little analogy with true seeds. Hence the vegetable kingdom is separated into two distinct groups, namely, the flowering (Phanerogamia), and the flowerless (Cryptogamia or Agamia). As the former usually possess a highly developed system of spiral and other vessels, while the latter are either altogether destitute of them, or have them only in a few of the highest orders, and those in a peculiar state, the flowering plants are termed Vasculares, and the flowerless Cellulares. And as all the flowering, or vascular plants, when they form stems, increase by an extension of their ends, and a distension or enlargement of their circumference, but the flowerless or cellular plants form their stems simply by the addition of new matter to their points, the latter are called Acrogens, signifying increase from the summit.

Flowering plants are also for the most part furnished with respiratory or breathing organs (stomata), of which the flowerless vegetables are to a great extent destitute.

The flowering or vascular plants are also divisible into two well marked groups, namely, the Exogens, or Dicotyledons, and the Endogens, or Monocotyledons.

The Exogens (growing from without), increase by the addition of new woody matter to the outside of the stems beneath the bark; and they are further characterized by the embryo having two or more cotyledons, or seed-lobes, hence they are also called Dicotyledons; such as the Elm, Beech, &c.

The Endogens, as we have previously stated, increase by the addition of ligneous matter to the inside of their stems near the centre; and as the embryo in this class has but one cotyledon, they are likewise termed monocotyledons, as the Cane, Palm, &c. Again, exogenous plants have the young external wood connected with a central pith, by medullary processes; while endogens do not possess such a structure, having no central pith. In exogens the veins (venation) of the leaves, are disposed in meshes, like net-work, but in endogens the veins run parallel to each other.

The number of parts in the flower of an exogenous plant is usually five, or its multiples: in the endogens it is commonly three, or its multiples. In the germination, the young root of exogens is a mere extension of the radicle; but in endogens it is protruded from within.

Thus, in the flowering or vascular plants, we have two groups distinct from each other in their germination, the structure of their stems and leaves, their mode of growth, the arrangement of the parts of the flower, and in the structure of the embryo.

The vegetable kingdom is thus separated into three natural classes,--1, the Exogens, 2, the Endogens, 3, the Acrogens; but there are likewise other divisions, a knowledge of which is of great importance in the study of fossil botany; the sub-class termed Gymnosperms especially requires notice.

In the strictly exogenous and endogenous plants, the fertilizing principle is communicated to the young seeds through the medium of a stigma and style, that terminate the case or pericarp in which the seeds are enclosed: but in another important group of the vegetable kingdom, the pollen is directly applied to the ovule, without the intervention of any pericarpial apparatus; hence these are termed Gymnosperms, signifying naked seeds. These plants have the same relation to the other exogens, as frogs and analogous reptiles bear to the other orders of their Class; they comprise the two natural orders Coniferæ, and Cycadaceæ.

The Gymnosperms also possess peculiarities of a subordinate nature: thus, many kinds have more than two cotyledons, and are therefore termed polycotyledons; again, the radicle usually adheres to the albumen in which the embryo lies, hence they are sometimes named Synorhiza. The veins of the leaves (in those whose leaves are veined), are either simple or forked; in which respect they approach the endogens on the one hand, and the acrogens on the other.

This concise definition of the natural divisions of the vegetable kingdom will enable the reader to comprehend the botanical principles which must guide him in his attempt to explore the ancient floras, whose fossil remains are generally found in a very fragmentary condition.

I need only add that M. Ad. Brongniart, in his great work on Fossil Plants, arranges the vegetable kingdom into five classes, viz.:--

1. Cellular Cryptogamia,[36] or Amphigens.

2. Vascular Cryptogamia,[37] or Acrogens.

3. Monocotyledons.[38]

4. Gymnospermous Dicotyledons.[39]

5. Angiospermous Dicotyledons.[40]

[36] Plants having the fructification concealed, and of cellular structure only.

[37] Plants having the fructification concealed, and with vessels, or vascular tissue.

[38] Flowering plants with one cotyledon; the Endogens.

[39] Plants with naked seeds; that is, destitute of a pericarp or case.

[40] Plants with the seeds in a receptacle or pericarp, with a style and stigma.

ON THE MODE OF INVESTIGATING FOSSIL REMAINS OF VEGETABLES.

[Sidenote: INVESTIGATION OF FOSSIL PLANTS.]

The distinguished authors of the British Fossil Flora justly remark, that a few isolated, and very imperfect data, exclusively afforded by the remains of the organs of vegetation, are but too often the sole guide to the class, order, or genus of the fossil plants which the geologist has to examine; hence, in most instances, a general idea only can be obtained of the nature of the original.[41] To facilitate the study of Fossil Botany they offer some practical suggestions, which have served as the basis of the following directions for the investigation of vegetable remains, and which the previous remarks will, we trust, render intelligible.

[41] Foss. Flor. vol. I. p. xxvi.

1. The Trunk, or Stem.--Examine if the wood in a transverse section be disposed in concentric circles (as Plate V. fig 4): if so, it belonged to an exogenous tree: if, on the contrary, the wood appears deposited irregularly in spots (Lign. 1, fig. 4), then the original was endogenous. If a transverse section show remains of sinuous, unconnected layers, resembling arcs with their ends directed outwards, and of a solid structure, and imbedded among looser tissue, then it belonged to an arborescent fern; see the subjoined figures (Lign. 2).

[Sidenote: INVESTIGATION OF FOSSIL STEMS.]

If the stem be in a state of preservation that will admit of the slicing or chipping off a piece for microscopical investigation, the process described at the conclusion of this section should be employed.

The following data may be thus obtained. If the structure be entirely cellular, and it can be satisfactorily ascertained that it never possessed vascular tissue, the original belonged to the Cryptogamia; i.e. to fuci, mosses, and the like.

If it consist of parallel tubes, and has neither pith, nor rays passing from the centre to the circumference, the tree or plant was endogenous, like the Palm. If any trace be present of tissue crossing the longitudinal tubes at right angles, and radiating from the centre to the circumference, this will prove the existence of medullary rays, and the original must have been exogenous, as the Oak, Elm, &c.: and if in a transverse section the tubes appear of equal size, the tree was probably coniferous, or cycadeous (i.e. related to the plants called Cycas and Zamia); but if larger tubes appear among the smaller ones, disposed in a definite manner (see Plate V. fig. 4), it belonged to some other tribe of exogenous plants.

If the walls of the tubes be studded with glands (Lign. 1, fig. 1, c; Plate V. figs. 2^b 3^b.); the fossil belongs to the Coniferæ.

If any vestige of a central pith be discovered, the exogenous nature of the original is undoubted, for no other class, as we previously stated, possesses a central cellular column.

The absence or presence of a true cortical investment, or bark, is important, for a distinct bark is the characteristic of the exogenous class:[42] a cortical integument, or rind, not separable from the enclosed structure, indicates the monocotyledons; and the entire absence of any rind, the cryptogamia.

[42] An apparent exception to this rule is found in the fossil genus Clathraria, described hereafter, which has a distinct hollow cortical cylinder, that separates from the internal axis: this is not true bark, but is formed by the consolidation of the bases of the petioles or leaf-stalks; see Lign. 54.

The markings on the stems, occasioned by the scars or cicatrices left by the separation of the petioles or leaf-stalks (as on the stalk of a cabbage), afford important evidence, since they are commonly present, even when the cylindrical trunk is compressed into a flat thin layer of coal; as we shall often have occasion to remark. In this place it need only be stated, that by these scars may be detected the position of the leaves, and the form of the bases of the petioles or leaf-stalks; their probable direction, whether they were opposite, alternate, verticillate or spirally disposed, deciduous or persistent, imbricated or remote. Even when no traces of the leaves remain, the origin of the branches, and their bifurcation, may perhaps be determinable.

2. The Leaves.--In a fossil state the texture and surface of the leaves are sometimes preserved; but in general the outline of the leaf, its division and arrangement, and its mode of venation, can alone be ascertained. The venation, that is, the form and distribution of the vascular tissue, or vessels, through the leaf, is the most important character for our guidance; and Dr. Lindley offers the following suggestions on this point. If the veins be all parallel, not branched, or only connected by little transverse bars, and the leaves undivided (as in the Lily or Hyacinth), the plant was probably endogenous; but if the leaf be divided or pinnated, it may be referable to Cycadeæ (Lign. 45).

Leaves having the veins of equal, or nearly equal thickness, and dichotomous (forked), or very fine, and simply divided, belong to the fern tribe; to this division an immense proportion of the foliage found in the carboniferous strata is referable; the genera of fossil ferns have been constructed principally from the venation.

If the veins of a leaf be obviously of unequal thickness, and reticulated, or disposed in net-like meshes, as in the rose and apple, the original was dicotyledonous (Plate III, figs. 4, 8).

Leaves of a large size, destitute of veins, and irregularly divided, probably belong to fuci, or other marine plants (Lign. 10).

Such are the rules for the investigation and interpretation of the characters of stems and foliage, which have been preserved by mineralization. Their application is not difficult, and the student may by their assistance obtain some general indications as to the nature of the original trees or plants, whose petrified remains form the subject of his examination.

ON THE MICROSCOPICAL EXAMINATION OF FOSSIL VEGETABLES.

[Sidenote: MICROSCOPICAL EXAMINATION.]

Mr. Nicol, who first suggested the method now generally adopted for preparing fossil wood, coal, &c. for microscopical examination, and which was employed by Mr. Witham in the illustrations of his beautiful work on the structure of fossil plants,[43] has so clearly explained the process, that by a little practice the student will be able to prepare specimens sufficiently thin for every useful purpose. Several lapidaries in London, (see list at the end of this work,) polish and mount fossil vegetables and other substances, in a very superior manner; but their charges are high, and they frequently injure specimens by grinding them too thin, and thus obliterating structure. I would recommend that a small chip of the specimen, if possible in a radial direction, should be examined by reflected light, always beginning with the lowest object-glass and eye-piece, and ascending to the highest power; at first without any preparation;[44] subsequently the object should be immersed in oil of turpentine, which will render it somewhat transparent, and it then should be examined by transmitted light. By this exploration we may detect structure, and ascertain if the specimen be worth the trouble or expense of further preparation.

[43] Observations on Fossil Vegetables. 4to. 1833.

[44] The drawings in Plate V. figs. 2 and 3, of fossil coniferous wood, were from chips seen by reflected light, and without any preparation.

Coal may be prepared for examination, by removing with a sharp knife a thin pellicle, or a minute scraping; immerse it in a drop of oil of turpentine on a piece of glass; then add a little Canada balsam, and hold the glass over the flame of a lamp till the balsam is spread evenly over the specimen. But without any preparation, the surface of coal recently broken may be successfully investigated. One of the most interesting examples of coniferous structure in coal that my cabinet contains, was discovered by my son in a piece lying on the fire, which had been cracked by the heat; and I have another fragment, showing the spiral vessels, and coniferous glands, which the Rev. J. B. Reade obtained under similar circumstances. But for choice specimens, the following method is to be employed; and in many cases no other plan will succeed. Sections of teeth, bone, marble, &c. may be prepared by a like process.

MODE OF PREPARING SLICES OF FOSSIL WOOD FOR MICROSCOPICAL EXAMINATION.

"Let a thin slice be cut off from the fossil wood, in a direction perpendicular to the length of its fibres--the slice thus obtained must be ground perfectly flat, and polished. The polished surface is then to be cemented to a piece of plate glass (3 in. long and 1 in. wide) by Canada balsam--a thin layer of balsam must be applied to the polished surface of the slice, and also to one side of the glass--the slice and the glass are now to be laid on any thin plate of metal, and gradually heated over a slow fire, or a spirit lamp, to concentrate the balsam. The heat must not be so great as to throw the balsam into a state of ebullition; for if air bubbles be formed, it is difficult to get rid of them, and if not removed they will prevent the complete adhesion of the two surfaces when applied to each other; the heat of the metal should never be so great that the fingers may not be held in contact with it for a few seconds without inconvenience. When air bubbles are formed, they should be displaced by a small piece of wood tapering to a point; when the balsam is thought to be sufficiently concentrated, and all the air bubbles have disappeared, the slice and glass may be taken from the heated metal, and pressed closely together; a slight degree of pressure will suffice to expel the super-abundant balsam, and this will be facilitated by gently sliding the specimen to and fro on the glass; by this kind of motion any air that may have got entangled when the two surfaces were brought in contact, will also be removed. When the whole is cooled down to the temperature of the air, and the balsam has become solid, that part which adheres to the surface of the glass surrounding the slice should be scraped off with the point of a penknife; and by this operation, it will at once be seen whether the balsam has undergone the requisite concentration; for if it flakes off before the knife, it will be found that the slice and glass will cohere so firmly, that in the subsequent grinding, there will be no risk of their separating from each other; but if the balsam has not been sufficiently concentrated, it will slide before the knife, and in that case the two bodies will not adhere with requisite firmness. If the layer of balsam applied to the two surfaces be not too thick, its due concentration will be accomplished in four or five minutes, provided the application of the heat be properly regulated. The slice must now be ground to that degree of thinness which will permit its structure to be seen by the help of a microscope. This will be accomplished by rubbing the slice, by a rapid circular motion with the hand, on a piece of sheet lead, supplied with a little emery (size No. 1.) moistened with water; when the emery ceases to act, the muddy matter remaining should be removed, and a fresh portion of emery applied; this must be repeated until the surface of the slice is perfectly flat; a sheet of copper must then be substituted for the lead, and the fossil ground as smooth as possible by flower of emery, freed from its coarser parts. The surface may then be polished by friction, with crocus or rotten stone, on a transverse section of any soft wood."[45]

[45] Mr. Witham, Observations on Fossil Vegetables.Return to passage

V. ON PEAT-WOOD, LIGNITE, AND COAL

[Sidenote: PEAT-WOOD, LIGNITE, AND COAL.]

Before entering upon the examination of the specific and generic characters of fossil plants, and the natural relations of the extinct forms with those of the existing Floras, it will be requisite to notice those vast beds of vegetable matter, in various states of carbonization, which occur in the palæozoic, secondary, and tertiary formations.

Submerged Forests. Peat.--The phenomenon of extensive tracts of marsh-land, with layers of prostrate trees of all ages, lying but a few feet beneath the common alluvial soil, is of frequent occurrence, both inland, and in many places along the shores of our island. (Geol. S. E. p. 18). These submerged forests are generally situated below the level of the sea, and afford unquestionable proof of subsidences of the land. The trees are of the kinds indigenous to the districts in which they occur; and leaves and seeds of the hazel, beech, elm, &c. are often preserved in the silt in which the prostrate forests are imbedded. On the Sussex coast there are accumulations of this kind, at Bexhill, Pevensey levels, Felpham, &c.

The extensive subterranean forests exposed in the Fens of Lincolnshire by the operations carried on for draining that district, must be familiar to those who travel by the Great Northern Railway: the protruding upright stems, broken off at a short distance above the primitive soil, will remind the geological observer of the petrified forest of the Isle of Portland.

The wood in these cases has undergone no change but that of being dyed black, by an impregnation of solutions of iron; and many trunks are in so sound a state as to be employed in building. The oak timbers of the Royal George, lately raised up from off Portsmouth, after being immersed in silt about sixty years, closely resemble in colour and texture the wood of the submerged forests. Skeletons of deer, horse, swine, &c. are occasionally found imbedded in these subterranean accumulations of vegetable remains; and sometimes canoes, formed of the trunk of an oak, constructed by the aboriginal inhabitants of Britain, with stone implements called celts, are met with at considerable depths.

In the peat-bogs of Ireland (Wond. p. 66), large forest trees often occur, together with the skeletons of the elk, deer, and other animals of the chase; and in a few instances the bodies of the primitive hunters, wrapped in skins, have been discovered.

In Belfast Lough, a bed of peat is situated beneath the ordinary level of the waters, but is generally left bare at the ebb tides. Trunks and branches of trees, with vast quantities of hazel nuts, are imbedded in the peat; the whole being covered by layers of sand, and blue clay, or silt. In most cases the pericarps of the nuts are empty, the kernels having perished; but on the eastern side of the Lough, which is bounded by limestone rocks, they contain calc-spar, which in some examples forms a lining of delicate crystals (Plate V. fig. 6); while in others the kernel is transmuted into calcareous spar (see Plate III. fig. 7); but the pericarps are unchanged, and in the state of common dried nut-shells; the water which deposited the spar in their cavities not having left a particle of mineral matter in the ligneous substance through which it had filtrated.

In a subterranean forest at Ferry-bridge, Yorkshire, hazel nuts in a similar mineralized state occur, and the branches and stems of the trees have undergone a like change; the central ligneous axis is petrified, while the outer zones have undergone no lapidification, but remain in the state of dry rotten wood.[46]

[46] Specimens are preserved in the Museum at York.

[Sidenote: PEAT.--LIGNITE.--BROWN COAL.]

Lignite, Brown Coal, or Cannel Coal; these are terms employed to designate certain varieties of carbonized wood, in which the ligneous structure is more or less distinctly preserved. Lignite may be regarded as an imperfect coal, for in its chemical properties it holds an intermediate place between peat and bituminous coal. It is for the most part found in tertiary formations, but is not unfrequent in ancient secondary deposits, and may occur in the earliest sedimentary rocks which contain vegetable remains.

The newer deposits of Brown or wood-coal, are commonly situated in depressions or basins, as if they had been produced by the submergence of woods and forests, in a swamp or morass; and in many instances the ligneous structure is distinct in one part of the bed, while in another the mass is a pure black coal, differing in no respect from true coal, except that it is less dense.

Bovey Coal.--One of the most instructive deposits of brown coal in England, is that of Bovey Heathfield, near Chudleigh in Devonshire, which is of considerable thickness and extent, and presents all the characters of a true coal-field; namely, beds of carbonized vegetables, alternating with layers of clay and marl. The Bovey coal is in the state of bituminized wood, the vascular tissue (which is coniferous in the specimens that have come under my notice) being apparent. It is easily chipped or split, and leaves a considerable quantity of white ashes after combustion. The layers of coal vary in thickness from one foot to three feet; and there are eighteen or twenty in a depth of about 120 feet; this coal-field extends seven or eight miles. No leaves or fruits have been discovered; bitumen occurs both in the coal and in the intermediate clays. Calcareous spar, and iron pyrites, prevail in many of the strata. In some places this brown coal is covered by a bed of peat, in which trunks and cones of firs are imbedded. The whole series appears to have been a lacustrine deposit; probably formed in a lake, into whose basin rafts of pine forests were drifted by periodical land-floods. (Org. Rem. I. p. 327).

The brown-coal formations on the banks of the Rhine, present the same phenomena on a more extended scale, and complicated with changes induced by volcanic action. In Iceland, where at the present time forests are unknown, there are extensive deposits of lignite of a peculiar kind, termed surturbrand.

[Sidenote: JET.--WEALDEN COAL.]

Jet.--The beautiful substance called Jet, is a compact lignite, and the vascular tissue may be detected even in the most solid masses; when prepared in very thin slices, it appears of a rich brown colour by transmitted light, and the woody texture is visible to the naked eye. Jet is found in great purity and abundance in the cliffs of alum-shale on the Yorkshire coast, which were celebrated in the early centuries for the production of this substance. At Whitby and Scarborough extensive manufactories of ornaments and trinkets of jet are established. The sandstone cliffs near Whitby contain masses of a very compact variety, locally termed stone-jet. In the front of the cliff, on the north-west side of Haiburn Wyke, the stump of a tree was observed in an erect position, about three feet high, and fifteen inches in diameter; the roots traversed a bed of shale, and were in the state of coarse jet, but the trunk, which extended into the sandstone, was in part silicified, while other portions were decayed and had a sooty aspect.[47]

[47] Geological Survey of the Yorkshire Coast; by Rev. G. Young; 1828; p. 197.

Thin seams and layers, and nodular masses, as well as regular coal-fields of lignite, occur in the tertiary formations. At Castle Hill, near Newhaven, in Sussex (Wond. p. 239), a seam of lignite resembling the surturbrand of Iceland, a few inches thick, is interposed between strata of red marl in which are carbonized leaves of dicotyledonous trees.

At Alum Bay in the Isle of Wight, a layer of lignite occurs between the beds of vertical gravel and sand of that interesting locality.

Wealden Coal.--The Wealden formation, in some districts, contains layers of lignite, which alternate with finely laminated micaceous sandstones, marls, and clays, abounding in minute carbonized fragments of fern-leaves, with fresh-water shells, and entomostracous crustaceans. This series of strata so strikingly resembles in its general aspect the characters of a coal-field, that some years since extensive works were undertaken in Sussex, in the expectation that coal might be obtained of suitable quality for economical purposes. The search was unsuccessful, but the attempt deserves not the censure that was bestowed upon it, in the infancy of geological science;[48] for experience has since shown, that although the true coal-measures are only found beneath the Triassic and Permian formations, good combustible bituminous coal is not necessarily restricted to any period or series of strata, but may occur wherever the local conditions were favourable to the accumulation and bituminization of vegetable matter. In fact, the coal-fields of the north of Germany are of the Wealden epoch; and this coal more closely approaches in its chemical characters the black-coal of the ancient carboniferous formations, than any of the lignites and brown-coals of the tertiary strata. Some of the beds are highly bituminous, especially those of Schaumberg, and of the principality of Bückeburg, which may rank with the best English Newcastle coal; but those layers which are derived from coniferous trees and plants are more laminated, and somewhat resemble the brown-coal. These deposits have originated for the most part from carbonized conifers and cycads, with a few ferns and lycopodiaceæ, or club-mosses.

[48] See Sir J. F. W. Herschel's Discourse on Nat. Phil.

The brown-coal of Hohen-Warte by the Osterweld, is chiefly formed of the Abies Linkii, and Pterophyllum Lyellianum, whose leaves and twigs, closely impacted together, are generally of a brownish colour, have a glossy surface, and, when soaked in water, are perfectly flexible. The other modification of Wealden coal appears to have undergone a greater degree of pressure, and of exclusion from the atmosphere; no ligneous structure is apparent, but indistinct impressions of leaves are perceptible, and these are chiefly of ferns and club-mosses. This coal has probably resulted from an accumulation of plants of less firm texture, and more perishable, than those of which the former is composed.[49]

[49] See Dr. Bunker's Mon. Norddeutsch. Weald.

Many interesting facts relating to the carbonization of vegetables, came under my observation during my researches in the Wealden strata; and it is a subject of regret to me, that circumstances prevented my following up the investigation of those still imperfectly explored deposits. Small nodular portions of coal, in which no structure is apparent, often occur in the calciferous grit of Tilgate Forest; and sometimes large masses of lignite, fissured in every direction, and having the interstices filled with white calcareous spar.[50] Some of the sandstones are discoloured by the abundance of minute particles of lignite, produced by the disintegration of ferns peculiar to the country of the Iguanodon.

[50] A fine specimen of this kind is in the British Museum.

The original structure and composition of a plant doubtless affected its carbonization; for in the same layer of stone, the stems of Endogenites, hereafter described, invariably possess a thick, outer crust, of coal; while those of Clathrariæ, plants allied to the Cycads, have not a particle of carbonaceous matter, but are surrounded by a reddish brown earthy substance. The nature of the stratum in which the plants were imbedded, must also have influenced the process of bituminization. Masses of vegetables buried beneath beds of tenacious clay, by which the escape of the gaseous elements set free by decomposition was prevented, must have been placed under the most favourable conditions for their conversion into lignite and coal.

That the production of lignite is still going on there can be no doubt; and the following instance of a bed of recent origin, affords an instructive illustration of the subject. Near Limerick, in the district of Maine, one of the States of North America, there are peat-bogs of considerable extent, in which a substance similar to cannel-coal is found at the depth of three or four feet from the surface, amidst the remains of rotten logs of wood, and beaver-sticks:[51] the peat is twenty feet thick, and rests upon white sand. This coal was discovered on digging a ditch to drain a portion of the bog, for the purpose of obtaining peat for manure. The substance is a true bituminous coal, containing more bitumen than is found in any other variety,[AZ] Polished sections of the compact masses exhibit the peculiar structure of coniferous trees, and prove that the coal was derived from a species allied to the American fir.

[51] Pieces of wood fashioned by the beavers for the construction of their dams.

[52] An analysis of 100 grains gave the following results:--Bitumen 72; carbon, 21; oxide of iron, 4; silica, 1; oxide of manganese, 2; = 100.

[Sidenote: COAL.]

Coal.--We proceed to the examination of that remarkable substance which has resulted from the perfect bituminization of the vegetables of the most ancient Flora which geological researches have brought to light, and to which the term Coal is commonly restricted.

Although Balthazar Klein in the sixteenth century affirmed that coal owed its formation to wood and other vegetable substances,[53] yet I can well remember when many eminent geologists were sceptical on this point; and the truth in this, as in most other questions of natural philosophy, was established with difficulty. The experiments and observations of the late Dr. Macculloch, mainly contributed to solve the problem as to the vegetable nature of this substance; and that eminent chemist and geologist successfully traced the transition of vegetable matter from peat-wood, brown-coal, lignite, and jet, to coal, anthracite, graphite, and plumbago. Nor must the meritorious labours of that accomplished naturalist, and excellent man, the late Mr. Parkinson, author of the "Organic Remains of a Former World," in this field of research, be forgotten.[54] The first volume of that work, which treats on fossil plants, contains much original information on the transmutation of vegetables into the various mineral substances in which the nature and original structure of the originals are altogether changed and obliterated; it may still be consulted by the student with advantage.

[53] Sternberg's "Flore du Monde Primitif."

[54] See my "Pictorial Atlas of Organic Remains," 1850.

Although the vegetable origin of all coal will not admit of question, yet evidence of the internal organization of the plants of which it is composed, is not always attainable; for the most perfect coal has undergone a complete liquefaction, and if any portions of the structure remain, they appear under the microscope as if imbedded in a pure bituminous mass. The slaty coal generally preserves traces of cellular or vascular tissue, and the spiral vessels, and the dotted cells of coniferous trees, may readily be detected in chips or slices, prepared in the manner previously pointed out (ante, p. 66). In many examples the cells are filled with an amber-coloured resinous substance; in others the organization is so well preserved, that on the exposed surface of a piece of coal cracked by exposure to heat, the vascular tissue, spiral vessels, and cells studded with glands, may be detected. Even in the white ashes left after combustion, traces of the spiral vessels are often discernible under a highly magnifying powder. Some beds of coal are wholly composed of minute leaves and disintegrated foliage; and if a mass recently extracted from the mine be split asunder, the surface is seen to be covered with flexible pellicles of carbonized leaves and fibres, matted together; and flake after flake may be peeled off through a thickness of many inches, and the same structure be apparent. Rarely are any large trunks or branches observable in the coal; the appearance of many beds being that of a deposit of foliage, shed and accumulated in a forest, (as may be observable in existing pine-districts,) and consolidated by pressure, while undergoing that peculiar change by which vegetable matter is converted into a carbonaceous mass.

In fine, a gradual transition may be traced from the peat-wood and submerged forests of modern times, in which leaves, fruits, and trunks of indigenous trees and plants are preserved, to those vast deposits of mineral coal, formed by the bituminization of the extinct Floras which flourished in the palæozoic ages.

The geological position of the ancient coal, the manner in which it is interstratified with layers of clay, shale, micaceous sandstone, grit, and ironstone--in some districts associated with beds of fresh-water shells (Sil. Syst. p. 84)--in others alternating with strata containing marine remains,--are fully treated of in Wond. pp. 729-733, and Bd. p. 525; and it is not within the scope of the present work to dwell in detail upon what may be termed the physical geology of the carboniferous deposits. But a few observations on the phenomena presented by these accumulations of bituminized vegetables and their associated strata, are necessary to render the subsequent remarks on the habits and affinities of the plants composing the palæozoic Flora intelligible to the general reader.

While the essential conditions for the conversion of vegetable substances into coal appear to be the imbedding of large quantities of recent trees and plants in a deposit which shall exclude the air, and prevent the escape of the gaseous elements when released by decomposition from their organic combination, so, according to the more or less perfect manner in which these conditions are fulfilled, will result coal, jet, lignite, brown-coal, or peat-wood; or a mass of partially carbonized vegetables, like that observable when new-mown hay undergoes spontaneous combustion, from bituminous fermentation in the atmosphere (Wond. p. 701. Org. Rem. I. p. 181).

The manner in which the carboniferous strata have been deposited, has been a subject of much discussion. Some contend that the coal-measures were originally in the state of peat-bogs, and that the successive layers were formed by the subsidences of forests which grew on the sites now occupied by their carbonized remains; others suppose that the vegetable matter originated from rafts, like those of the Mississippi, which floated out to sea, and became engulfed; while many affirm that the coal-measures were accumulated in inland seas or lakes, the successive beds of vegetable matter being supplied by periodical land-floods; and the supporters of each hypothesis bring numerous facts in corroboration of their respective opinions. There can, I think, be no doubt that the production of coal has taken place under each of these conditions, and that at different periods, and in various localities, all these causes have been in operation; in some instances singly, in others in combination. Coal may have been formed at the bottom of fresh-water lakes, as in those instances where it is associated with fresh-water shells and crustaceans, as at Burdie House (Wond. p. 693), and in some of the Derbyshire and Yorkshire deposits; in the beds of rivers and estuaries, as in the Wealden, and in the Shrewsbury coal-field;[55] and from drifted forests, like the rafts of the American rivers, transported into the sea, and engulfed in the abyss of the ocean;[56] and the remains of terrestrial, lacustrine, and marine animals, may accordingly be found associated with it.[BE] But though many coal-fields (or basins, as they are termed, because they occupy depressions) have evidently been produced by different, and local agencies, the sedimentary deposits and coal-beds comprised in the carboniferous formations, setting aside unimportant variations, present a remarkable uniformity of character in their nature and arrangement, not only throughout Great Britain and Europe, but in every other part of the known world.

[55] In this coal-field are beds of limestone several feet thick, abounding in cyprides, fresh-water mollusks, &c.--Sil. Syst. p, 84.

[56] The immense thicknesss of some coal-beds, without any intercalations of earthy materials, seems to be inexplicable on any other supposition but that of accumulations of drift-wood and plants. In the Great Exhibition of 1851, there was exhibited, on the outside of the west end of the Crystal Palace, a section of the lowest bed of coal from Tividale Colliery in South Staffordshire, the total thickness of which was 29 feet, with no intermixture whatever of sediment, except some thin shaly partings: the entire mass was composed of carbonized vegetables.

[57] Sir R. I. Murchison has treated this subject with great ability: see Sil. Syst. chap, xi., and the illustrative maps opposite, p. 152.

[Sidenote: STRATIFICATION OF A COAL-FIELD.]

Stratification of a Coal-field.--The group of strata constituting a coal-field consists of an alternation of layers of coal and of clay, of variable thickness, resting, very generally, on grit, or marine limestone abounding in shells, corals, and crinoidea.

My late excellent friend, Mr. Bakewell, used to exemplify the manner in which the beds of coal are interstratified with layers of clay and shale, by the following apt illustration; let a series of mussel-shells be placed one within the other, and a layer of clay be interposed between each; the shells will represent the beds of coal, and the partitions of clay the earthy strata intercalated between the carboniferous layers; now, if one side of the series of shells be raised to indicate the general rise of the strata in that direction, and the whole be dislocated by partial cracks and fissures, the general arrangement and subsequent displacement of the beds will be represented.

The principal feature which arrests attention on the examination of the section of a coal-pit, is the uniform presence of a thick bed of clay beneath every layer of coal; but a still more extraordinary fact remains to be mentioned, namely, that a common plant of the coal strata, called Stigmaria, (hereafter described, see Lign. 36, 38,) invariably occurs, more or less abundantly, in this bed of under-day, although very rarely to be met with in the coal or shale above. This phenomenon, long since noticed by Martin, Macculloch, and other authors, but whose value was not duly estimated till the recent observations of Mr. Logan, (Geol. Proc. vol. iii. p. 275,) is also found to prevail throughout the Welsh coal formation, which is upwards of twelve thousand feet in thickness, and contains more than sixty beds of coal, and as many of clay with stigmariæ; the Appalachian coal-measures of the United States present the same characters.[58] To place this fact before the student in a clear point of view, I will describe one of the triple series of beds which compose a coal-field.

[58] See Prof. Rogers, in the Proceedings of the American Geologists, p. 453; and Sir C. Lyell's Travels in America.

1. Under-clay; the lowermost stratum. A tough argillaceous substance, which upon drying becomes a grey friable earth: it is occasionally black, from the presence of carbonaceous matter. It contains innumerable stems of stigmariæ, which are generally of considerable length, and have their rootlets or fibres (see Lign. 38) attached, and extending in every direction through the clay: these stems commonly lie parallel with the planes of the bed, and nearer to the top than to the bottom.

2. Coal. A carbonized mass, in which the external forms of the plants and trees composing it are obliterated, but the internal structure remains; large trunks or stems, and leaves, are rarely distinguishable in it, but the presence of coniferous wood in many beds of coal, proves that this arises, not from the absence of trees, but from their external forms having been obliterated.

3. The Roof, or upper bed. This generally consists of slaty clay, abounding in leaves, trunks, stems, branches, and fruits, and contains layers and nodules of ironstone, inclosing leaves, insects, crustaceans, &c.

In some localities beds of fresh-water mussels, and in others of marine shells, are intercalated; layers of shale, finely laminated clay, micaceous sand and grit, and pebbles of limestone, granite, sandstone, and other rocks, are often present. The most illustrative examples of the foliage of the carboniferous flora are found in this deposit, which appears to be an accumulation of drifted materials derived from other rocks, and promiscuously intermingled with the dense foliage and stems of a prostrate forest; the whole having been transported from a distance by a powerful current or flood.

[Sidenote: ORIGIN AND NATURE OF COAL.]

Thus we have, in the first place, spread uniformly over the bottom, and constituting the bed on which the coal reposes, a stratum of clay (Under-clay), composed of fine pulverulent materials, which may have once constituted the soil of a vast plain or savannah; the only remains found in it are the roots of gigantic trees (see Lign. 36); for such the stigmariæ are now proved to have been, and not aquatic plants, as was formerly supposed (Bd. p. 476).

Secondly, a bituminous mass (Coal), composed of coniferous wood, gigantic ferns, club-mosses, &c.; occasionally with trunks of trees penetrating vertically through it.

Thirdly, a deposit of drift or water-worn materials (the Roof), mixed with the foliage and stems of numerous species of terrestrial plants; the whole appearing to have been subjected to the action of currents. The first, or Under-clay, may have been the natural soil, in which the stigmariæ grew; the next,--the Coal,--the carbonized stems, and other remains of the trees to which the roots belonged: and the last, or uppermost, forming the roof of the coal, may have resulted from the foliage and branches of a prostrate forest, overwhelmed and buried beneath the transported detritus of distant rocks.

These phenomena may be explained by supposing the inundation of a thickly-wooded plain from an irruption of the sea; or of a vast inland lake, occasioned by the sudden removal of some barrier; or by a subsidence of the tract of country on which the forest grew. But when we find an accumulation of strata, in which triple deposits of this kind are repeated some thirty or forty times through a thickness of many thousand feet, this solution of the problem is not satisfactory. Not only subsidence after subsidence must have taken place, but the first submergence have been followed by an elevation of the land--another soil, fit for the growth of forest trees, must have been produced--another generation of vegetables, of precisely the same species and genera, have sprung up, and arrived at maturity--and then another subsidence, and another accumulation of drift. And these periodical oscillations in the relative level of the land and water must have gone on uninterruptedly through a long period of time, not in one district or country only, but in various parts of the world, during the same geological epoch. At present I do not think we have data sufficient to explain these phenomena; what has been advanced may, perhaps, serve to elicit further information, by pointing out the difficulties in which the question is involved, and showing what interesting fields of discovery are still unexplored, and how comprehensive and important are the objects that come within the scope of geological investigation.[59]

[59] I would refer the student for a fuller consideration of the phenomena thus briefly noticed, to the 6th edition of my Wonders of Geology, pp. 669, 718, 731.

* * * * *

I will conclude this chapter with the following beautiful reflections of Dr. Buckland on the origin and nature of Coal, and the changes it undergoes when rendered subservient to the necessities and luxuries of man.

"Few persons are aware of the remote and wonderful events in the economy of our planet, and of the complicated applications of human industry and science, which are involved in the production of the coal that supplies with fuel the metropolis of England.

"The most early stage to which we can carry back its origin, was among the swamps and forests of the primeval earth, where it flourished in the form of gigantic Calamites, and stately Lepidodendra, and Sigillariæ. From their native bed, these plants were transported into some adjacent lake, or estuary, or sea. Here they floated on the waters, until they sank saturated to the bottom, and being buried in the detritus of adjacent lands, became transferred to a new estate among the members of the mineral kingdom. A long interment followed, during which a course of chemical changes, and new combinations of their vegetable elements, converted them to the mineral condition of coal. By the elevating force of subterranean agency, these beds of coal have been uplifted from beneath the waters, to a new position in the hills and mountains, where they are accessible to the industry of man. From this fourth stage, coal has been removed by the labours of the miner, assisted by the arts and sciences, that have co-operated to produce the steam-engine, and the safety-lamp. Returned once more to the light of day, and a second time committed to the waters, it has, by the aid of navigation, been conveyed to the scene of its next and most considerable change by fire; a change during which it becomes subservient to the most important wants and conveniences of man. In this seventh stage of its long eventful history, it seems, to the vulgar eye, to undergo annihilation; its elements are, indeed, released from the mineral combinations which they have maintained for ages, but their apparent destruction is only the commencement of new successions of change and of activity. Set free from their long imprisonment, they return to their native atmosphere, from which they were absorbed by the primeval vegetation of the earth. To-morrow they may contribute to the substance of timber, in the trees of our existing forests; and having for a while resumed their place in the living vegetable kingdom, may, ere long, be applied a second time to the use and benefit of man. And when decay or fire shall once more consign them to the earth, or to the atmosphere, the same elements will enter on some further department of their perpetual ministration in the economy of the material world."[60]

[60] Bd p. 481.Return to passage

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I. On the Nature and Arrangement of the British Strata and their Fossils, 15

II. Fossil Botany, 51

III. Fossil Zoology, 216

XVI. Fossil Reptiles; Enaliosaurians and Crocodiles, 643

IV. Geological Excursions, 827

Introduction

Part I

II. FOSSIL BOTANY

III. FOSSIL ZOOLOGY

Part IV

Part I

Chapter I

II. SYNOPSIS OF THE BRITISH STRATA

III. ON THE NATURE OF FOSSILS, OR ORGANIC REMAINS

Part II

IV. FOSSIL BOTANY

V. ON PEAT-WOOD, LIGNITE, AND COAL