tpy BRARY IIVERSITY OF ALIFORNIA EARTH SCIENCES IBRARY . PRINCIPLES GEOLOGY, AN ATTEMPT TO EXPLAIN THE FORMER CHANGES OF THE EARTH'S SURFACE, BY REFERENCE TO CAUSES NOW IN OPERATION. CHARLES LYELL, ESQ., F.R.S., FOR. SEC. TO THE GEOL. SOC., PROF. OF GEOL. TO K/.VG'S COLL., LOXDOX. ' Amid all the revolutions of the globe the economy of Nature has been uniform, and her laws are the only things that have resisted the general movement. The rivers and the rocks, the seas and the continents have been changed in all their parts ; but the laws which direct those changes, and the rules to which they are subject, have remained invariably the same.* PJ.AYFAIR, Illustrations of the Huttonian Theory, $374. IX THREE VOLUMES. VOL. I. THE SECOND EDITION. LONDON: JOHN MURRAY, ALBEMARLE-STREET. XI DC CC XXXI I. GIFT OF LONDON: Printed by WILLIAM CLOWKS, Stamford Street. MATTHEW LIBRARY 0. TO THE VERY REVEREND WILLIAM BUCKLAND, D.D., F.R S., F.G.S., 8fc. Sfc. Sfe. PROFESSOR OF GEOLOGY IN THE UNIVERSITY OF OXFORD. MY DEAR DR. BUCKLAND, The favourable reception of the first edition encourages me to offer the dedication of this volume to you, who first instructed me in the elements of Geology, and by whose energy and talents the cultivation of the science in this country has been so eminently promoted. I am, My dear Dr. BUCKLAND, Very sincerely yours, CHARLES LYELL. London, June 10, 1832. M126631 b2 ADVERTISEMENT. I HAVE availed myself of the present opportunity to make occasional corrections and additions throughout the work. The additions, however, are not considerable, the increased size of the volume being chiefly due to the adoption of a more open type, and the insertion of headings to the different sub- divisions of each chapter, which it is hoped will facilitate reference, and render the arrangement of the subject-matter more clear to the student. CONTENTS. PAGE CHAPTER I. GEOLOGY defined Compared to History Its relation to other Physical Sciences Its distinctness from all Not to be confounded with Cosmogony 1 CHAPTER II. Oriental Cosmogony Doctrine of the successive destruction and renovation of the world Origin of this doctrine Common to the Egyptians Adopted by the Greeks System of Pythagoras Of Aristotle Dogmas concerning the extinction and reproduction of genera and species Strabo's theory of elevation by earthquakes Pliny Concluding Remarks on the knowledge of the Ancients . . . . 6 CHAPTER III. Arabian writers of the tenth century Persecution of Omar Cosmogony of the Koran Early Italian writers Fracastoro Controversy as to the real nature of organized fossils Fossil shells attributed to the Mosaic deluge Palissy Steno Scilla Quirini Boyle Plot Hooke's Theory of Eleva- tion by earthquakes His speculations on lost species of animals Ray Physico-theological writers Woodward's Diluvial Theory Burnet Whis- ton Hutchinson Leibnitz Vallisneri Lazzaro Moro Generelli Buffon His theory condemned by the Sorbonne as unorthodox Buffon's declara- tion Targioni Arduino Michell Catcott Raspe Fortis Testa Whitehurst Pallas Saussure . . . . . .24 CHAPTER IV. Werner's application of Geology to _the art of Mining Excursive charac- ter'of his Lectures Enthusiasm of his pupils His" authority His theoreti- cal errors Desmarest's Map and Description of Auvergne Controversy between the Vulcanists and Neptunists Intemperance of the rival Sects Button's Theory of the Earth His discovery of Granite. Veins Originality of his Views Why opposed Playfair's Illustrations Influence of Vol- taire's Writings on Geology Imputations cast on the Huttonians by Wil- liams, Kirwan, and De Luc Smith's Map of England Geological Society Vlll CONTENTS. PAGE of London Progress of the science in France Growing importance of the study of organic remains . . . . .63 CHAPTER V. Review of the causes which have retarded the progress of Geology Effects of prepossessions in regard to the duration of past time Of preju- dices arising from our peculiar position as inhabitants of the land Of those occasioned by our not seeing subterranean changes now in progress All these causes combine to make the former course of Nature appear different from the present Several objections to the assumption, that existing causes have produced the former changes of the earth's surface, removed by modern discoveries . . . . . . . .85 CHAPTER VI. Further examination of the question as to the discordance of the ancient and modern causes of change Proofs that the climate of the Northern hemisphere was formerly hotter Direct proofs from the organic remains of the Sicilian and Italian strata Proofs from analogy derived from extinct Quadrupeds Imbedding of Animals in Icebergs Siberian Mammoths Evidence in regard to temperature, from the fossil remains of tertiary and secondary rocks From the Plants of the Coal formation . . .105 CHAPTER VII. Further examination of the question as to the discordance of the ancient and modern causes of change On the causes of vicissitudes in climate Re- marks on the present diffusion of heat over, the globe On the dependence of the mean temperature on the relative position of land and sea Isother- mal lines Currents from equatorial regions Drifting of icebergs Different temperature of Northern and Southern hemispheres Combination of causes which might produce the extreme cold of which the earth's surface is sus- ceptible On the conditions necessary for the production of the extreme of heat, and its probable effects on organic life. . . . 120 CHAPTER VIII. Further examination of the question as to the discordance of the ancient and modern causes of change That the geographical features of the northern hemisphere, at the period of the deposition of the carboniferous strata, were such as might, according to the theory before explained, have given rise to an extremely hot climate State of the surface when the tran- sition and mountain limestones, coal-sandstones, and coal originated Change in the physical geography of northern latitudes, between the era of the formation of the carboniferous series and the lias Character of organic remains, from the lias to the chalk inclusive State of the surface CONTENTS. IX PAGE when these deposits originated Great accession of land, and elevation of mountain-chains, between the consolidation of the newer secondary and older tertiary rocks Consequent refrigeration of climate Abrupt transition from the organic remains of the secondary to those of the tertiary strata Maes- tricht beds Remarks on the theory of the diminution of central heat. . 144 CHAPTER IX. Further discussion of the question as to the discordance of the ancient and modern causes of change Theory of the progressive development of organic life Evidence in its support wholly inconclusive Vertebrated animals in the oldest strata Differences between the organic remains of successive formations Remarks on the comparatively modern origin of the human race The popular doctrine of successive development not confirmed by the admission that man is of modern origin Introduction of man, to what ex- tent a change in the system . CHAPTER X. Division of the subject into changes of the organic and inorganic world Inorganic causes of change divided into the aqueous and igneous Aqueous causes Destroying and transposing power of running water Sinuosities of rivers Two streams when united do not occupy a bed of double surface Heavy matter removed by torrents and floods Recent inundations in Scotland Effects of ice in removing stones Erosion of chasms through hard rocks Excavations in the lavas of Etna by Sicilian rivers Gorge of the Simeto Gradual recession of the cataracts of Niagara Speculations as to the time required for their reaching Lake Erie. . .192 CHAPTER XI. Action of running water, continued Course of the Po Desertion of its old channel Artificial embankments of the Po, Adige, and other Italian rivers Basin of the Mississippi Its meanders Islands Shifting of its course Raft of the Atchafalaya Drift wood New-formed lakes in Loui- siana Earthquakes in the valley of the Mississippi Floods caused by land- slips in the White mountains Bursting of a lake in Switzerland Devasta- tions caused by the Anio at Tivoli. . . . . 210 CHAPTER XII. Difference between the transporting power of springs and rivers Many springs carry matter from below upwards Mineral ingredients most abun- dant in springs Connexion of mineral waters with volcanic phenomena Calcareous springs Travertin of the Elsa Baths of San Vignone and of San Filippo, near Radicofani Spheroidal structure in travertin, as in Eng- lish maguesian limestone Bulicami of Viterbo Lake of the Solfatara, X CONTENTS. PAGE near Rome Travertin at Cascade of Tivoli Ferruginous Springs Cement- ing and colouring property of iron Brine Springs Carbonated Springs Disintegration of Auvergne granite Caverns in limestone Petroleum Springs Pitch Lake of Trinidad ..... 227 CHAPTER XIII. Reproductive effects of running water Division of Deltas into lacustrine, mediterranean, and oceanic Lake deltas Growth of the delta of the Rhone in the Lake of Geneva Chronological computations of the age of deltas Recent deposits in Lake Superior Deltas of inland seas Rapid shallowing of the Baltic Arguments for and against the hypothesis of Celsius Elevated beaches on the coast of Sweden Marine delta of the Rhone Various proofs of its increase Stony nature of its deposits Delta of the Po, Adige, Isonzo, and other rivers entering the Adriatic Rapid conversion of that gulf into laud Mineral characters of the new deposits Delta of the Nile Its increase since the time of Homer Its growth why checked at present. . . 252 CHAPTER XIV. Oceanic deltas Delta of the Ganges and Burrampooter Its size, rate of advance, and nature of its deposits Formation and destruction of islands Abundance of crocodiles Inundations Delta of the Mississippi Deposits of drift wood Gradual filling up of the Yellow Sea Rennell's estimate of the mud carried down by the Ganges Formation of valleys illustrated by the growth of deltas Grouping of new strata in general Convergence of deltas Conglomerates Various causes of stratification Direction of laminse Remarks on the interchange of land and sea. .... 275 CHAPTER XV. Destroying and transporting effects of tides and cxirrents Shifting of their position Differences in the rise of the tides Velocity of currents Causes of currents Action of the sea on the British coast Shetland Islands Large blocks removed Effects of lightning Breach caused in a mass of porphyry Isles reduced to clusters of rocks Orkney Isles East coast of Scotland Stones thrown up on the Bell Rock East coast of England Waste of the cliffs of Holderness, Norfolk, and Suffolk Silting up of estuaries Origin of submarine forests Yarmouth estuary Submarine forests Suffolk coast Duuwich Essex coast Estuary of the Thames Goodwin sands Coast of Kent Formation of Straits of Dover South coast of England Coast of Sussex Coast of Hants Coast of Dorset Portland Origin of the Chesil Bank Cornwall Lionnesse tradition Coast of Brittany. . . 293 CONTENTS, CHAPTER XVI. Action of Tides and Currents, continued Inroads of the sea upon the delta of the Rhine in Holland Changes in the arms of the Rhine Estuary of the Bies Bosch, formed in 1421 Formation of the Zuyder Zee, in the 13th century Islands destroyed Delta of the Ems converted into a Bay Estuary of the Dollart formed Encroachment of the sea on the coast of Sleswick Inroads on the Eastern shores of North America Tidal wave called the Bore Influence of tides and currents on the mean level of seas Action of currents in inland lakes and seas Baltic Cimbrian deluge- Straits of Gibraltar Under-currents Shores of Mediterranean Rocks transported on floating icebergs Dunes of blown sand Sands of the Libyan Desert De Luc's natural chronometers. . ... 326 CHAPTER XVIL Reproductive effects of Tides and Currents Silting'up of Estuaries does not compensate the loss of land on the borders of the ocean Bed of the German Ocean Composition and extent of its sand-banks Strata deposited by cur- rents on the southern and eastern shores of the Mediterranean Transporta- tion by currents of the sediment of the Amazon, Orinoco, and Mississippi Stratification Concluding remarks. ..... 346 CHAPTER XVIII. Changes of the inorganic world, continued Igneous causes Division of igneous agents into the vulcano and the earthquake Distinct regions of sub- terranean disturbance Region of the Andes System of volcanos extending from the Aleutian isles to the Moluccas Polynesian archipelago Volcanic region extending from the Caspian Sea to the Azores Former connexion of the Caspian with Lake Aral and the Sea of Azof Low steppes skirting these seas Tradition of deluges on the shores of the Bosphorus, Hellespont, and the Grecian archipelago Periodical alternation of earthquakes in Syria and Southern Italy Western limits of the European region Earthquakes rarer and more feeble in proportion as we recede from the centres of volcanic action Extinct volcanos not to be included in lines of active vents. . 353 CHAPTER XIX. History of the volcanic eruptions in the district round Naples Early con- vulsions in the island of Ischia Numerous cones thrown up there Epomeo not an habitual volcano Lake Avernus The Solfatara Renewal of the eruptions of Vesuvius A.D. 79 Pliny's description of the phenomena Re- marks on his silence respecting the destruction of Herculaneum and Pompeii Subsequent history of Vesuvius Lava discharged in Ischia in 1302 Pause in the eruptions of Vesuvius Monte Nuovo thrown up Uniformity of the volcanic operations of Vesuvius and the Phlegraean Fields in ancient and modern times. .... 375 Xll CONTENTS. PAGE CHAPTER XX. Volcanic district of Naples, continued Dimensions and structure of the cone of Vesuvius Dikes iu the recent cone, how formed Section through Ve- suvius and Sorama Vesuvian lavas and minerals Effects of decomposition on lavas Alluvions called ( aqueous lavas' Origin and composition of the matter enveloping Herculaneum and Pompeii Controversies on the subject Condition and contents of the buried cities Proofs of their having suffered by an earthquake Small number of skeletons State of preservation of ani- mal and vegetable substances Rolls of Papyrus Probability of future dis- coveries of MSS. Stabiae Torre del Greco Concluding remarks on the destroying and renovating agency of the Campanian volcanos. . 390 CHAPTER XXI. External physiognomy of Etna Minor cones produced by lateral eruptions Successive obliteration of these cones Early eruptions of Etna Monti Rossi thrown up in 1669 Great fissure of S. Lio Towns overflowed by lava Part of Catania destroyed Mode of the advance of a current of lava Ex- cavation of a church under lava Series of subterranean caverns Linear direction of cones formed in 1811 and 1819 Flood produced in 1755 by the melting of snow during an eruption A glacier covered by a lava-stream on Etna Volcanic eruptions in Iceland New island thrown up iu 1783 Two lava currents of Skaptur Jokul in the same year Their immense volume Eruption of Jorullo in Mexico Humboldt's Theory respecting the convexity of the Plain of Malpais. . . . . . . 414 CHAPTER XXII. Volcanic archipelagos The Canaries Eruptions of the Peak of TenerifFe Cones thrown up iu Lancerote iu 1730-36 Pretended distinction between ancient and modern lavas Recent formation of oolitic travertin in Lancerote Grecian Archipelago Santoriu and its contiguous isles New islands thrown up in the Gulf of Santorin Von Btich's Theory of ' Elevation Craters' considered Supposed ' Crater of Elevation' in the Isle of Palma Descrip- tion of the Caldera of Palma Barren island in the Bay of Bengal Origin of the deep gorge on the side of ' Elevation Craters' Stratification of submarine volcanic products Causes of the great size of the craters of submarine vol- canos Cone of Somma formed in the same manner as that of Vesuvius Mineral composition of volcanic products Speculations respecting the nature of igneous rocks produced at great depths by modern volcanic eruptions. 435 CHAPTER XXIII. Earthquakes and their effects Deficiency of ancient accounts Ordinary atmospheric phenomena Changes produced by earthquakes in modern times considered in chronological order Earthquake in Murcia, 1829 Island of CONTENTS. Xlll PAGE Ischia in 1828 Bogota in 1827 Chili in 1822 Great extent of country elevated Aleppo in 1822 Ionian Isles in 1820 Island of Surabawa in 1815 Town of Tomboro submerged Earthquake of Cutch in 1819 Subsidence of the delta of the Indus Earthquake of Caraccas in 1812 South Carolina in 1 811 Geographical changes in the valley of the Mississippi Volcanic con- vulsions in the Aleutian Islands in 1806 Reflections on the earthquakes of the nineteenth century Earthquake in Quito, 1797 Cumana, 1797 Ca- raccas, 1790 Sicily, 1790 Java, 1786 Sinking down of large tracts . 457 CHAPTER XXIV. Earthquake in Calabria, February 5th, 1783 Shocks continued to the end of the year 1786 Authorities Extent of the area convulsed Geological structure of the district Difficulty of ascertaining changes of relative level even on the sea-coast Subsidence of the quay at Messina Shift or fault in the Round Tower of Terranuova Movement in the stones of two obelisks Alternate opening and closing of fissures Cause of this phenomenon Large edifices engulphed Dimensions of new caverns and fissures Gradual closing in of rents Bounding of detached masses into the air Landslips Build- ings transported entire to great distances Formation of fifty new lakes Currents of mud Small funnel-shaped hollows in alluvial plains Fall of cliffs along the sea-coast Shore near Scilla inundated State of Stromboli and Etna during the shocks Illustration afforded by this earthquake of the mode in which valleys are formed . . . 475 CHAPTER XXV. Earthquakes of the eighteenth century, continued Guatimala, 1777 Java, 1772 Truncation of a lofty cone Caucasus, 1772 Java, 1771 St. Domingo, 1770 Colombia, 1766 Chili, 1760 Azores, 1757 Lisbon, 1755 Sinking down of the quay to the depth of six hundred feet Shocks felt throughout Europe, Northern Africa, and the West Indies Great wave Shocks felt at sea St. Domingo, 1751 Conception Bay, 1750 Permanent elevation of the bed of the sea to the height of twenty-four feet Peru, 1746 Kamtschatka, 1737 Martinique, 1727 Iceland, 1725 Teneriffe, 1706 Java, 1699 Landslips obstruct the Batavian and Tangarau rivers Quito, 1698 Sicily, 1693 Subsidence of land Moluccas, 1693 Jamaica, 1692 Large tracts engulphed Portion of Port Royal sunk from twenty to fifty feet under water The Blue Mountains shattered Reflections on the amount of change in the last one hundred and forty years Proofs of ele- vation and subsidence of land on the coast of the Bay of Baiae Evidence of the same afforded by the present state of the Temple of Serapis . .502 XIV CONTENTS. CHAPTER XXVI. PAGE Magnitude of the subterranean changes produced by earthquakes at great depths below the surface Obscurity of geological phenomena no proof of want of uniformity in the system, because subterranean processes are but little understood Reasons for presuming the earthquake and volcano to have a common origin Probable analogy between the agency of steam in the Icelandic geysers, and in volcanos during eruptions Effects of hydrostatic pressure of high columns of lava Of the condensation of vapours in the interior of the earth That some earthquakes may be abortive eruptions Why all volcanos are in islands or maritime tracts Gases evolved from volcanos Regular discharge of heat and of gaseous and earthy matter from the subterranean regions Cause of the wave-like motion and of the retreat of the sea during earthquakes Difference of circumstances of heat and pressure at great depths Inferences from the superficial changes brought about by earthquakes In what manner the repair of land destroyed by aqueous causes takes place Proofs that the sinking in of the earth's crust somewhat exceeds the forcing out by earthquakes Geological consequences of this hypothesis, that there is no ground for presuming that the degree of force exerted by sub- terranean movements in a given time has diminished Concluding remarks . 551 LIST OF PLATES AND WOOD-CUTS IN THE FIRST VOLUME. PLATES. Frontispiece. This representation of the present state of the Temple of Serapis has been carefully reduced from that given by the Canonico Andrea de Jorio in his ' Ricerche sul Tempio di Serapide, in Puzzuoli.' Napoli, 1820. Plate I. Jig. 1. Showing that a chain of volcanic vents surrounds the Asiatic Islands, in the same manner as a continuation of the same line skirts the eastern borders of the continent of Asia. This plate is copied from plate 13 of Von Buch's Phys. Besch. der Canarischen Inseln. Berlin, 1825. The position, however, of some of the volcanos, and the outline of several of the islands, has been corrected. Fig. 2. Showing the direction of the trachytic islands from N.W. to S.E. parallel to the principal mountain-chains of Greece, as also to the Grecian islands which constitute a continuation of the mountains of the main land, and are of the same mineral composition. This plate is also copied from Von Buch, plate 12, p. 365. Plate II. fig. 1. -View of the islands of Ischia and Procida, with part of the coast of Misenum, taken from part of plate 17 of Sir William Hamilton's Campi Phlegrsei. Fig. 2. Map of the Volcanic district of Naples. This map is copied from one constructed by G. P. Scrope, Esq., to illustrate a memoir in the Geol. Trans., vol. ii. part iii., from unpublished maps of Captain Smyth, R.N., p. 375, WOOD-CUTS. o. PAGE 1. Transverse section of the Italian peninsula . . . 156 2. Diagram explanatory of the sinuosity of river-courses . . 196 3. Diagram showing the recent excavation of lava at the foot of Etna by the river Simeto ...... 205 4. Section of travertin of San Vignone .... 232 xvi WOOD -CUTS. NO. 5. Section of spheroidal concretionary travertin seen in descending from the Temple of Vesta, under the Cascade of Tivoli . . 240 C. Section on the banks of the Arve at its confluence with the Rhone, showing the stratification of deposits where currents meet . 291 7. Cut representing stony fragments drifted by the sea at Northmavine, Shetland ....... 298 8. View of the ' Grind of the Navir,' a passage forced by the sea through rocks of hard porphyry in the Shetland Isles . . . 300 9. Granitic rocks named the Drongs, between Papa Stour and Hillswick Ness, Shetland ...... 301 10. Drongs to the south of Hillswick Ness, Shetland . 301 11. View of Monte Nuovo, formed in the Bay of Baise, September 29th, 1538 ....... 385 12. View of the volcanos of the Phlegrsean Fields . . . 38G 13. Diagram exhibiting a supposed section of Vesuvius and Somma 394 14. View of Monti Rossi on the flanks of Etna, formed in 1669 . 418 15. Chart and section of Santorin and the contiguous islands in the Grecian Archipelago . . . . . . 441 16. View of the Isle of Palma, and of the Caldera in its centre . 444 17- View of the cone arid crater of Barren Island in the Bay of Bengal 446 18. Supposed section of the same .... 450 19. Deep fissure nearPolistenain Calabria caused by the earthquake of 1783 480 20. Shift or fault in the round tower of Terranuova in Calabria occasioned by the earthquake of 1783 . . . . 481 21 . Horizontal shift in the stones of two obelisks in the Convent of S. Bruno 482 22. Fissures near Jerocarne in Calabria caused by the earthquake of 1783 483 23. Chasm formed by the earthquake near Oppido in Calabria . 485 24. Chasm in the hill of St. Angelo, near Soriano in Calabria, caused by the. earthquake in 1783 * .... 486 25. Circular pond nearPolistena in Calabria caused by the same earthquake 486 26. Change of the surface at Fra Ramondo, near Soriano in Calabria 490 27. Landslips near Cinquefrondi caused by earthquake of 1783 . 492 28. Circular hollows in the plain of Rosarno formed by the same earthquake 493 29. Section of one of them . . . . 494 30. Ground plan of the coast of the Bay of Baise in the environs of Puzzuoli 518 31. Section exhibiting the relation of the recent marine deposits to the more ancient in the Bay of Baise to the north of Puzzuoli . 519 32. Section exhibiting the same relation to the south-east . 519 33. View of the crater of the Great Geyser in Iceland . . 536 34. Supposed section of the subterranean reservoir and pipe of a Geyser in Iceland 538 PRINCIPLES OF GEOLOGY. CHAPTER I. Geology defined Compared to History Its relation to other Physical Sciences Its distinctness from all Not to be confounded with Cosmogony. GEOLOGY is the science which investigates the successive changes that have taken place in the organic and inorganic kingdoms of nature; it inquires into the causes of these changes, and the influence which they have exerted in modify- ing the surface and external structure of our planet. By these researches into the state of the earth and its inha- bitants at former periods, we acquire a more perfect knowledge of its present condition, and more comprehensive views con- cerning the laws now governing its animate and inanimate productions. When we study history we obtain a more pro- found insight into human nature, by instituting a comparison between the present and former states of society. We trace the long series of events which have gradually led to the actual posture of affairs ; and by connecting effects with their causes, we are enabled to classify and retain in the memory a multitude of complicated relations the various peculiarities of national character the different degrees of moral and intellectual refinement, and numerous other circumstances, which, without historical associations, would be uninteresting or imperfectly understood. As the present condition of nations is the result of many antecedent changes, some ex- tremely remote and others recent, some gradual, others sudden and violent, so the state of the natural world is the result of a long succession of events, and if we would enlarge VOL. I. B 52* * * " OBQL06Y "COMPARED TO HISTORY. [Ch. I. our experience of the present economy of nature, we must in- vestigate the effects of her operations in former epochs. We often discover with surprise, on looking back into the chronicles of nations, how the fortune of some battle has influ- enced the fate of millions of our contemporaries,, when it has long been forgotten by the mass of the population. With this remote event we may find inseparably connected the geogra- phical boundaries of a great state, the language now spoken by the inhabitants, their peculiar manners, laws, and religious opinions. But far more astonishing and unexpected are the connexions brought to light, when we carry back our re- searches into the history of nature. The form of a coast, the configuration of the interior of a country, the existence and extent of lakes, valleys, and mountains, can often be traced to the former prevalence of earthquakes and volcanos, in regions which have long been undisturbed. To these remote convul- sions the present fertility of some districts, the sterile character of others,, the elevation of land above the sea, the climate, and various peculiarities, may be distinctly referred. On the other hand, many distinguishing features of the surface may often be ascribed to the operation at a remote era of slow and tran- quil causes to the gradual deposition of sediment in a lake or in the ocean, or to the prolific increase of testacea and corals therein. To select another example, we find in certain localities subterranean deposits of coal, consisting of vegetable mat- ter, formerly drifted into seas and lakes. These seas and lakes have since been filled up, the lands whereon the forests grew have disappeared or changed their form, the rivers and currents which floated the vegetable masses can no longer be traced, and the plants belonged to species which for ages have passed away from the surface of our planet. Yet the com- mercial prosperity, and numerical strength of a nation, may now be mainly dependent on the local distribution of fuel determined by that ancient state of things. Geology is intimately related to almost all the physical Ch. I.] ITS RELATION TO OTHER PHYSICAL SCIENCES. sciences, as is history to the moral. An historian should, if possible, be at once profoundly acquainted with ethics, politics, jurisprudence, the military art, theology ; in a word, with all branches of knowledge, whereby any insight into human affairs, or into the moral and intellectual nature of man, can be ob- tianed. It would be no less desirable that a geologist should be well versed in chemistry, natural philosophy, mineralogy, zoology, comparative anatomy, botany ; in short, in every science relating to organic and inorganic nature. With these accomplishments the historian and geologist would rarely fail to draw correct and philosophical conclusions from the various monuments transmitted to them of former occurrences. They would know to what combination of causes analogous effects were referrible, and they would often be enabled to supply by inference, information concerning many events unrecorded in the defective archives of former ages. But the brief duration of human life, and our limited powers, are so far from per- mitting us to aspire to such extensive acquisitions, that excel- lence even in one department is within the reach of few, and those individuals most effectually promote the general progress, who concentrate their thoughts on a limited portion of the field of inquiry. As it is necessary that the historian and the cultivators of moral or political science should reciprocally aid each other, so the geologist and those who study natural his- tory or physics stand in equal need of mutual assistance. A comparative anatomist may derive some accession of knowledge from the bare inspection of the remains of an extinct quadru- ped, but the relic throws much greater light upon his own science, when he is informed to what relative era it belonged, what plants and animals were its contemporaries, in what degree of latitude it once existed, and other historical details. A fossil shell may interest a conchologist, though he be igno- rant of the locality from which it came ; but it will be of more value when he learns with what other species it was associated, whether they were marine or fresh-water, whether the strata B 2 4 GEOLOGY DISTINCT FROM COSMOGONY. [Ch. I. containing them were at a certain elevation above the sea, and what relative position they held in regard to other groups of strata, with many other particulars determinable by an expe- rienced geologist alone. On the other hand, the skill of the comparative anatomist and conchologist are often indispensable to those engaged in geological research, although it will rarely happen that the geologist will himself combine these different qualifications in his own person. Some remains of former organic beings, like the ancient temple, statue, or picture, may have both their intrinsic and their historical value, while there are others which can never be expected to attract attention for their own sake. A painter, sculptor, or architect, would often neglect many curious relics of antiquity, as devoid of beauty and uninstruc- tive with relation to their own art, however illustrative of the progress of refinement in some ancient nation. It has there- fore been found desirable that the antiquary should unite his labours to those of the historian, and similar co-operation has become necessary in geology. The field of inquiry in living nature being inexhaustible, the zoologist and botanist can rarely be induced to sacrifice time in exploring the imperfect remains of lost species of animals and plants, while those still existing afford constant matter of novelty. They must entertain a desire of promoting geology by such investigations, and some knowledge of its objects must guide and direct their studies. According to the different opportunities, tastes, and talents of individuals, they may employ themselves in collecting particular kinds of mine- rals, rocks, or organic remains, and these, when well ex- amined and explained, afford data to the geologist, as do coins, medals, and inscriptions to the historian. It was long ere the distinct nature and legitimate objects of geology were fully recognized, and it was at first confounded with many other branches of inquiry, just as the limits of his- tory, poetry, and mythology were ill-defined in the infancy of civilization. Werner appears to have regarded geology as Ch. I.] GEOLOGY DISTINCT FROM COSMOGONY. 5 little other than a subordinate department of mineralogy, and Desmarest included it under the head of Physical Geography. But the identification of its objects with those of Cosmogony has been the most common and serious source of confusion. The first who endeavoured to draw a clear line of demarcation between these distinct departments, was Hutton, who declared that geology was in no ways concerned ' with questions as to the origin of things.' We shall attempt in the sequel of this work to demonstrate that geology differs as widely from cosmogony, as speculations concerning the creation of man differ from history. But before we enter more at large on this controverted question, we shall endeavour to trace the progress of opinion on this topic, from the earliest ages, to the commencement of the pre- sent century. CHAPTER II. Oriental Cosmogony Doctrine of the successive destruction and renovation of the world Origin of this doctrine Common to the Egyptians Adopted hy the Greeks System of Pythagoras Of Aristotle Dogmas concerning the extinction and reproduction of genera and species Strabo's theory of eleva- tion by earthquakes Pliny Concluding Remarks on the knowledge of the Ancients. Oriental Cosmogony. THE earliest doctrines of the Indian and Egyptian schools of philosophy, agreed in ascribing the first creation of the world to an omnipotent and infinite Being. They concurred also in representing this Being, who had existed from all eternity, as having repeatedly destroyed and reproduced the world and all its inhabitants. In the ' Insti- tutes of Menu,' the sacred volume of the Hindoos, to which, in its present form, Sir William Jones ascribes an antiquity of at least eight hundred and eighty years before Christ, we find this system of the alternate destruction and renovation of the world, proposed in the following remarkable verses. 'The Being, whose powers are incomprehensible, having created me (Menu) and this universe, again became absorbed in the supreme spirit, changing the time of energy for the hour of repose. * When that power awakes, then has this world its full expansion ; but when he slumbers with a tranquil spirit, then the whole system fades away For while he reposes as it were, embodied spirits endowed with principles of action depart from their several acts, and the mind itself becomes inert.' Menu then describes the absorption of all beings into the Supreme essence, and the Divine soul itself is said to slumber, and to remain for a time immersed in ' the first idea, or in darkness.' He then proceeds, (verse fifty-seven,) ' Thus that immutable power, by waking and reposing alternately, revivi- Ch. II.] INSTITUTES OF MENU. 7 fies and destroys, in eternal succession, this whole assemblage of locomotive and immoveable creatures.' It is then declared that there has been a long succession of manivantaras, or periods, each of the duration of many t;hou- sand ages, and ' There are creations also, and destructions of worlds innu- merable : the Being, supremely exalted, performs all this with as much ease as if in sport, again and again for the sake of conferring happiness*/ The compilation of the ordinances of Menu was not all the work of one author nor of one period, and to this circumstance some of the remarkable inequalities of style and matter are probably attributable. There are many passages, however, wherein the attributes and acts of the ' Infinite and Incom- prehensible Being' are spoken of with much grandeur of conception and sublimity of diction, as some of the passages above cited, though sufficiently mysterious, may serve to ex- emplify. There are at the same time such puerile conceits and monstrous absurdities in the same cosmogony, that some may impute to mere accident any slight approximation to truth, or apparent coincidence between the oriental dogmas and observed facts. This pretended revelation, however, was not purely an effort of the unassisted imagination, nor invented without regard to the opinions and observations of naturalists. There are introduced into the same chapter, certain astronomi- cal theories, evidently derived from observation and reasoning. Thus, for instance, it is declared that, at the North Pole, the year was divided into a long day and night, and that their long day was the northern, and their night the southern course of the sun ; and to the inhabitants of the moon, it is said, one day is equal in length to one month of mortals f. If such statements cannot be resolved into mere conjectures, we have no right to refer, to mere chance, the prevailing notion, that * Institutes of Hindoo Law, or the Ordinances of Menu, from the Sanscrit, translated by Sir William Jones, 1796. f Menu Inst., c. i. 66 and 67. 8 ORIENTAL COSMOGONY. [Ch. II. the earth and its inhabitants had formerly undergone a succes- sion of revolutions and catastrophes, interrupted by long inter- vals of tranquillity. Now there are two sources in which such a theory may have originated. The marks of former convulsions on every part of the surface of our planet are obvious and striking. The remains of marine animals imbedded in the solid strata are so abundant, that they may be expected to force themselves on the observation of every people who have made some progress in refinement ; and especially where one class of men are ex- pressly set apart from the rest for study and contemplation. If these appearances are once recognized, it seems natural that the mind should come to the conclusion, not only of mighty changes in past ages, but of alternate periods of repose and disorder of repose when the fossil animals lived, grew, and multiplied of disorder, when the strata wherein they were buried became transferred from the sea to the interior of con- tinents, and entered into high mountain chains. Those modern writers, who are disposed to disparage the former intellectual advancement and civilization of eastern nations, might concede some foundation of observed facts for the curious theories now under consideration, without indulging in exaggerated opinions of the progress of science ; especially as universal catastrophes of the world, and exterminations of organic beings, in the sense in which they were understood by the Brahmin, are un- tenable doctrines. We know that the Egyptian priests were aware, not only that the soil beneath the plains of the Nile, but that also the hills bounding the great valley, contained marine shells ; and it could hardly have escaped the observation of Eastern phi- losophers, that some soils were filled with fossil remains, since so many national works were executed on a magnificent scale by oriental monarchs in very remote eras. Great canals and tanks required extensive excavations ; and we know that in more recent times (the fourteenth century of our era) the re- moval of soil necessary for such undertakings, brought to . II.] ORIENTAL COSMOGONY. light geological phenomena, which attracted the attention of a people less civilized than were many of the older nations of the East *. But although we believe the Brahmins, like the priests of Egypt, to have been acquainted with the existence of fossil remains in the strata, it is probable that the doctrine of succes- sive destructions and renovations of the world merely received corroboration from such proofs ; and that it was originally handed down, like the religious dogmas of most nations, from a ruder state of society. The true source of the system must be sought for in the exaggerated traditions of those partial, but often dreadful catastrophes, which are sometimes occasioned by various combinations of natural causes. Floods and vol- canic eruptions, the agency of water and fire, are the chief instruments of devastation on our globe. We shall point out in the sequel the extent of these calamities, recurring at distant intervals of time, in the present course of nature ; and shall only observe here, that they are so peculiarly calculated to inspire a lasting terror, and are so often fatal in their conse- quences to great multitudes of people, that it scarcely requires the passion for the marvellous, so characteristic of rude and half-civilized nations, still less the exuberant imagination of eastern writers, to augment them into general cataclysms and conflagrations. Humboldt relates the interesting fact, that after the anni- hilation of a large part of the inhabitants of Cumana, by an earthquake in 1766, a season of extraordinary fertility ensued, * This circumstance is mentioned in a Persian MS. copy of the historian Fe- rishta, in the library of the East India Company, relating to the rise and progress of the Mahomedan Empire in India, agd procured from the library of Tippoo Sultan in 1 799 ; and has been recently referred to at some length by Dr. Buckland. (Geol. Trans., 2d Series, vol. ii. part iii. p. 389.) It is stated that, in the year 762 (or 1360 of our era), the king employed fifty thousand labourers in cutting through a mound, so as to form a junction between the rivers Selima and Sutluj, and in this mound were found the bones of elephants and men, some of them petrified, and some of them resembling bone. The gigantic dimensions attributed to the human bones show them to have belonged to some of the larger pachi- dermata. 10 EGYPTIAN COSMOGONY. [Ch. II. in consequence of the great rains which accompanied the sub- terranean convulsions. The Indians/ he says, celebrated, after the ideas of an antique superstition, by festivals and dancing, the destruction of the world and the approaching epoch of its regeneration *.' The existence of such rites among the rude nations of South America is most important, for it shows what effects may be produced by great catastrophes of this nature, recurring at distant intervals of time, on the minds of a barbarous and un- cultivated race. The superstitions of a savage tribe are trans- mitted through all the progressive stages of society, till they exert a powerful influence on the mind of the philosopher. He may find, in the monuments of former changes on the earth's surface, an apparent confirmation of tenets handed down through successive generations, from the rude hunter,, whose terrified imagination drew a false picture of those awful visita- tions of floods and earthquakes, whereby the whole earth as known to him was simultaneously devastated. Egyptian Cosmogony. Respecting the cosmogony of the Egyptian priests, we gather much information from writers of the Grecian sects, who borrowed almost all their tenets from Egypt, and amongst others that of the former successive de- struction and renovation of the world f. We learn from Plutarch, that this was the theme of one of the hymns of Orpheus, so celebrated in the fabulous ages of Greece. It was brought by him from the banks of the Nile ; and we even find in his verses, as in the Indian systems, a definite period assigned for the duration of each successive world J. The returns of great catastrophes were determined by the period of the Annus Magnus, or great year, a cycle composed of the re- volutions of the sun, moon, and planets, and terminating when these return together to the same sign whence they were sup- * Humboldt et Bonpland, Voy. Relat. Hist., vol. i. p. 30. f Prichard's Egypt. Mythol., p. 177. J Plut. de Defectu Oraculorum, cap. 12. Censorinus de Die Natali. See also Prichard's Egypt. Mythol., p. 182. Ch. II.] EGYPTIAN COSMOGONY. 11 posed at some remote epoch to have set out. The duration of this great cycle was variously estimated. According to Or- pheus, it was 120,000 years ; according to others, 300,000 ; and by Cassander it was taken to be 360,000 years*. We learn particularly from the Timoeus of Plato, that the Egyptians believed the world to be subject to occasional con- flagrations and deluges, whereby the gods arrested the career of human wickedness, and purified the earth from guilt. After each regeneration, mankind were in a state of virtue and hap- piness, from which they gradually degenerated again into vice and immorality. From this Egyptian doctrine, the poets derived the fable of the decline from the golden to the iron age. The sect of Stoics adopted most fully the system of catastrophes destined at certain intervals to destroy the world. These they taught were of two kinds the Cataclysm, or destruc- tion by deluge, which sweeps away the whole human race, and annihilates all the animal and vegetable productions of nature ; and the Ecpyrosis, or conflagration, which dissolves the globe itself. From the Egyptians also they derived the doctrine of the gradual debasement of man from a state of innocence. Towards the termination of each era the gods could no longer bear with the wickedness of men, and a shock of the elements or a deluge overwhelmed them ; after which calamity, Astrea again descended on the earth, to renew the golden agef. The connexion between the doctrine of successive catastro- phes and repeated deteriorations in the moral character of the human race, is more intimate and natural than might at first be imagined. For, in a rude state of society, all great calami- ties are regarded by the people, as judgments of God on the wickedness of man. Thus, in our own time, the priests per- suaded a large part of the population of Chili, and perhaps believed themselves, that the great earthquake of 1822 was a sign of the wrath of heaven for the great political revolution just then consummated in South America. In like manner, in the account given to Solon by the Egyptian priests, of the sub- * Pilchard's Egypt. Mythol., p. 182. f Ibid., p. 193. 12 EGYPTIAN COSMOGONY. [Ch. II. mersion of the island of Atlantis under the waters of the ocean, after repeated shocks of an earthquake, we find that the event happened when Jupiter had seen the moral depravity of the inhabitants*. Now, when the notion had once gained ground, whether from causes before suggested or not, that the earth had been destroyed by several general catastrophes, it would next be inferred that the human race had been as often de- stroyed and renovated. And, since every extermination was assumed to be penal, it could only be reconciled with divine justice, by the supposition that man, at each successive crea- tion, was regenerated in a state of purity and innocence. A very large portion of Asia, inhabited by the earliest na- tions whose traditions have come down to us, has been always subject to tremendous earthquakes. Of the geographical boundaries of these, and their effects, we shall, in the proper place, have occasion to speak. Egypt has, for the most part, been exempt from this scourge, and the tradition of catas- trophes in that country was perhaps derived from the East. One extraordinary fiction of the Egyptian mythology was the supposed intervention of a masculo-feminine principle, to which was assigned the development of the embryo world, somewhat in the way of incubation. For the doctrine was, that when the first chaotic mass had been produced, in the form of an egg, by a self-dependent and eternal Being, it required the mysterious functions of this masculo-feminine demi-urgus to reduce the component elements into organized forms. Although it is scarcely possible to recall to mind this con- ceit without smiling, it does not seem to differ essentially in principle from some cosmological notions of men of great genius and science in modern Europe. The Egyptian philo- sophers ventured on the perilous task of seeking out some analogy to the mode of operation employed by the Author of Nature in the first creation of organized beings, and they compared it to that which governs the birth of new individuals * Plato's Timoeus. ch jj -j EGYPTIAN COSMOGONY. 13 by generation. To suppose that some general rules might be observed in the first origin of created beings, or the first intro- duction of new species into our system, was not absurd, nor inconsistent with anything known to us in the economy of the universe. But the hypothesis, that there was any analogy between such laws, and those employed in the continual repro- duction of species once created, was purely gratuitous. In like manner, it is not unreasonable nor derogatory to the attri- butes of Omnipotence, to imagine that some general laws may be observed in the creation of new worlds ; and if man could witness the birth of such worlds, he might reason by induction upon the origin of his own. But in the absence of such data, an attempt has been made to fancy some analogy between the agents now employed to destroy, renovate, and perpetually vary the earth's surface, and those whereby the first chaotic mass was formed, and brought by supposed nascent energy from the embryo to the habitable state. By how many shades the elaborate systems, constructed on these principles, may differ from the mysteries of the ' Mun- dane Egg' of Egyptian fable, we shall not inquire. It would, perhaps, be dangerous ground, and some of our contemporaries might not sit as patiently as the Athenian audience, when the fiction of the chaotic egg, engrafted by Orpheus upon their own mythology, was turned into ridicule by Aristophanes. That comedian introduced his birds singing, in a solemn hymn, ' How sable-plumaged Night conceived in the boundless bosom of Erebus, and laid an egg, from which, in the revolution of ages., sprung Love, resplendent with golden pinions. Love fecundated the dark- winged chaos, and gave origin to the race of birds*." Pythagorean Doctrines. Pythagoras, who resided for more than twenty years in Egypt, and, according to Cicero, had visited the East, and conversed with the Persian philosophers, introduced into his own country, on his return, the doctrine of the gradual deterioration of the human race from an original * Aristophanes' Birds, 694. 14 PYTHAGOREAN SYSTEM. [Ch. II. state of virtue and happiness ; but if we are to judge of his theory concerning the destruction and renovation of the earth, from the sketch given by Ovid, we must concede it to have been far more philosophical than any known version of the cosmologies of Oriental or Egyptian sects. Although Pytha- goras is introduced by the poet as delivering his doctrine in person, some of the illustrations are derived from natural events which happened after the death of the philosopher. But notwithstanding these anachronisms, we may regard the account as a true picture of the tenets of the Pythagorean school in the Augustan age ; and although perhaps partially modified, it must have contained the substance of the original scheme. Thus considered, it is extremely curious and instruc- tive ; for we here find a comprehensive and masterly summary of almost all the great causes of change now in activity on the globe, and these adduced in confirmation of a principle of per- petual and gradual revolution inherent in the nature of our terrestrial system. These doctrines, it is true, are not directly applied to the explanation of geological phenomena ; or, in other words, no attempt is made to estimate what may have been, in past ages, or what may hereafter be, the aggregate amount of change brought about by such never-ending fluc- tuations. Had this been the case, we might have been called upon to admire so extraordinary an anticipation with no less interest than astronomers, when they endeavour to divine by what means the Samian philosopher came to the knowledge of the Copernican theory. Let us now examine the celebrated passages to which we have been adverting* : ' Nothing perishes in this world ; but things merely vary and change their form. To be born, means simply that a thing begins to be something different from what it was before; and dying, is ceasing to be the same thing. Yet, although no- thing retains long the same image, the sum of the whole remains constant.' These general propositions are then confirmed by a series of examples, all derived from natural appearances, * Ovid's Metamor., lib. 15. Ch. II.] PYTHAGOREAN SYSTEM. 15 except the first, which refers to the golden age giving place to the age of iron. The illustrations are thus consecutively adduced. 1. Solid land has been converted into sea. 2. Sea has been changed into land. Marine shells lie far distant from the deep, and the anchor has been found on the summit of hills. 3. Valleys have been excavated by running water, and floods have washed down hills into the sea *. 4. Marshes have become dry ground. 5. Dry lands have been changed into stagnant pools. 6. During earthquakes some springs have been closed up, and new ones have broken out. Rivers have deserted their channels, and have been re-born elsewhere ; as the Erasinus in Greece, and Mysus in Asia. 7. The waters of some rivers, formerly sweet, have become bitter, as those of the Anigris in Greece, &c. f 8. Islands have become connected with the main land by the growth of deltas and new deposits, as in the case of Antissa joined to Lesbos, Pharos to Egypt, &c. 9. Peninsulas have been divided from the main land, and have become islands, as Leucadia ; and according to tradition Sicily, the sea having carried away the isthmus. 10. Land has been submerged by earthquakes : the Grecian cities of Helice and Buris, for example, are to be seen under the sea, with their walls inclined. 11. Plains have been upheaved into hills by the confined air seeking vent, as at Traezen in the Peloponnese. 12. The temperature of some springs varies at different periods. The waters of others are inflammable j. * Eluvie mons est deductus in oequor, v. 267. The meaning of this last verse is somewhat obscure, but taken with the context, may be supposed to allude to the abrading power of floods, torrents, and rivers. f The impregnation from new mineral springs, caused by earthquakes in vol- canic countries, is, perhaps, here alluded to. * This is probably an allusion to the escape of inflammable gas, like that in the district of Baku, west of the Caspian ; at Pietra-mala, in the Tuscan Apennines; and several other places. 16 PYTHAGOREAN SYSTEM. [Ch. II 13. There are streams which have a petrifying power, and convert the substances which they touch into marble. 14. Extraordinary medicinal and deleterious effects are pro- duced by the water of different lakes and springs *. 15. Some rocks and islands, after floating, and having been subject to violent movements, have at length become stationary and immoveable, as Delos, and the Cyanean Isles f. 16. Volcanic vents shift their position ; there was a time when Etna was not a burning mountain, and the time will come when it will cease to burn. Whether it be that some caverns become closed up by the movements of the earth, and others opened, or whether the fuel is finally exhausted, &c. &c. The various causes of change in the inanimate world having been thus enumerated, the doctrine of equivocal generation is next propounded, as illustrating a corresponding perpetual flux in the animate creation J. In the Egyptian and Eastern cosmogonies, and in the Greek version of them, no very definite meaning can, in general, be * Many of those described seem fanciful fictions, like the virtues still so com- monly attributed to mineral waters. f Raspe, in a learned and judicious essay (De Novis Insulis, chap. 19), has made it appear extremely probable that all the traditions of certain islands in the Mediterranean having at some former time frequently shifted their positions, and at length become stationary, originated in the great change produced in their form by earthquakes and submarine eruptions, of which there have been modern examples in the new islands raised in the time of history. When the series of con- vulsions ended, the island was said to become fixed. J It is not inconsistent with the Hindoo mythology to suppose that Pythagoras might have found in the East not only the system of universal and violent catas- trophes and periods of repose in endless succession, but also that of periodical revolutions, effected by the continued agency of ordinary causes. For Brahma, Vishnu, and Siva, the first, second, and third persons of the Hindoo triad, seve- rally represented the Creative, the Preserving, and the Destroying powers of the Deity. The co-existence of these three attributes, all in simultaneous operation, might well accord with the notion of perpetual but partial alterations finally bringing about a complete change. But the fiction expressed in the verses be- fore quoted from Menu, of eternal vicissitudes in the vigils and slumbers of the Infinite Being, seems accommodated to the system of great general catastrophes followed by new creations and periods of repose. . Ch. II.] ARISTOTELIAN SYSTEM. 17 attached to the term ' destruction of the world/ for sometimes it would seem almost to imply the annihilation of our planetary system, and at others a mere revolution of the surface of the earth. Opinions of Aristotle. From the works now extant of Aris- totle, and from the system of Pythagoras, as above exposed, we might certainly infer that these philosophers considered the agents of change now operating in Nature, as capable of bring- ing about in the lapse of ages a complete revolution ; and the Stagyrite even considers occasional catastrophes, happening at distant intervals of time, as part of the regular and ordinary course of Nature. The deluge of Deucalion, he says, affected Greece only, and principally the part called Hellas, and it arose from great inundations of rivers during a rainy winter. But such extraordinary winters, he says, though after a certain period they return, do not always revisit the same places*. Censorinus quotes it as Aristotle's opinion, that there were general inundations of the globe, and that they alternated with conflagrations, and that the flood constituted the winter of the great year, or astronomical cycle, while the conflagration, or destruction by fire, is the summer or period of greatest heat *f*. If this passage, as Lipsius supposes, be an amplification, by Censorinus, of what is written in f the Meteorics,' it is a gross misrepresentation of the doctrine of the Stagyrite, for the general bearing of his reasoning in that treatise tends clearly in an opposite direction. He refers to many examples of changes now constantly going on, and insists emphatically on the great results which they must produce in the lapse of ages. He instances particular cases of lakes that had dried up, and deserts that had at length become watered by rivers and fer- tilized. He points to the growth of the Nilotic delta since the time of Homer, to the shallowing of the Palus Maeotis within sixty years from his own time, and although, in the same chap- ter, he says nothing of earthquakes, yet in others of the same * Meteor, lib. i. cap. xii. f De Die Nat. VOL. I. C 18 ARISTOTELIAN SYSTEM. [Ch. II. treatise *, he shows himself not unacquainted with their effects. He alludes, for example, to the upheaving of one of the Eolian islands, previous to a volcanic eruption. ' The changes of the earth, he says, are so slow in comparison to the duration of our lives, that they are overlooked (XavOavsi) ; and the migrations of people after great catastrophes, and their removal to other regions, cause the event to be forgotten f .' When we consider the acquaintance displayed by Aristotle with the destroying and renovating powers of Nature in his various works, the introductory and concluding passages of the twelfth chapter of his ( Meteorics' are certainly very re- markable. In the first sentence he says, ' the distribution of land and sea in particular regions does not endure throughout all time, but it becomes sea in those parts where it was land, and again it becomes land where it was sea, and there is reason for thinking that these changes take place according to a cer- tain system, and within a certain period.' The concluding observation is as follows : * As time never fails, and the universe is eternal, neither the Tanais, nor the Nile, can have flowed for ever. The places where they rise were once dry, and there is a limit to their operations, but there is none to time. So also of all other rivers; they spring up and they perish; and the sea also continually deserts some lands and invades others. The same tracts, therefore, of the earth are not some always sea, and others always continents, but every thing changes in the course of time.' It seems, then, that the Greeks had not only derived from preceding nations, but had also, in some slight degree, deduced from their own observations, the theory of great periodical re- volutions in the inorganic world \ there is, however, no ground for imagining that they contemplated former changes in the races of animals and plants. Even the fact, that marine re- mains were inclosed in solid rocks, although observed by many, and even made the groundwork of geological speculation, never stimulated the industry or guided the inquiries of naturalists, * Lib. ii, cap. 14, 15, and 16. f Ibid. Ch. II.] CREATION OF SPECIES. 19 It is not impossible that the theory of equivocal generation might have engendered some indifference on this subject, and that a belief in the spontaneous production of living beings from the earth, or corrupt matter, might have caused the or- ganic world to appear so unstable and fluctuating, that pheno- mena indicative of former changes would not awaken intense curiosity. The Egyptians, it is true, had taught, and the Stoics had repeated, that the earth had once given birth to some monstrous animals, which existed no longer; but the prevailing opinion seems to have been, that after each great catastrophe the same species of animals were created over again. This tenet is implied in a passage of Seneca, where, speaking of a future deluge, he says, * Every animal shall be generated anew, and men free from guilt shall be given to the earth*.' An old Arabian version of the doctrine of the successive revolutions of the globe, translated by Abraham Ecchellensis-f-, seems to form a singular exception to the general rule, for here we find the idea of different genera and species having been created. The Gerbanites, a sect of astronomers who flourished some centuries before the Christian era, taught as follows : ' That after every period of thirty-six thousand years, there were produced twenty-five pair of every species of animals, male and female, from whom animals might be pro- pagated and inhabit this lower world. But when a circulation of the heavenly orbs was completed, which is finished in that space of years, other genera and species of animals are propa- gated, as also of plants and other things, and the first order is destroyed, and so it goes on for ever and ever J.' * Omne ex integro animal generabitur, dabiturque terris homo inscius scelerura. Quest. Nat. iii. c. 29. t This author was Regius Professor of Syriac and Arabic at Paris, where, in 1685, he published a Latin Translation of many Arabian MSS. on different depart- ments of philosophy. This work has always been considered of high authority. J Gerbanitae docebant singulos triginta sex mille annos quadringentos, viginti quinque bina ex singulis animalium speciebus produci, marem scilicet ac feminam, ex quibus animalia propagantur, huncque inferiorem incolunt orbem. Absoluts C 2 20 THEORY OF STRABO. [Ch. II* Theory of Strabo. As we learn much of the tenets of the Egyptian and Oriental schools in the writings of the Greeks, so many speculations of the early Greek authors are made known to us in the works pf the Augustan and later ages. Strabo, in particular, enters largely, in the Second Book of his Geography, into the opinions of Eratosthenes and other Greeks on one of the most difficult problems in geology, viz., by what causes marine shells came to be plentifully buried in the earth at such great elevations and distances from the sea. He notices, amongst others, the explanation of Xanthus the Lydian, who said that the seas had once been more extensive, and that they had afterwards been partially dried up, as in his own time many lakes, rivers, and wells in Asia had failed during a season of drought. Treating this conjecture with merited disregard, Strabo passes on to the hypothesis of Strato, the natural philosopher, who had observed that the quantity of mud brought down by rivers into the Euxine was so great, that its bed must be gradually raised, while the rivers still continued to pour in an undiminished quantity of water. He therefore conceived that, originally, when the Euxine was an inland sea, its level had by this means become so much elevated that it burst its barrier near Byzantium, and formed a com- munication with the Propontis, and this partial drainage had already, he supposed, converted the left side into marshy ground, and that, at last, the whole would be choked up with soil. So, it was argued, the Mediterranean had once opened a passage for itself by the Columns of Hercules into the Atlan- autem ccelestium orbium circulatione, quae illo annorum conficitur spatio, iterum alia producuntur animalium genera et species, quemadmodum et plantarum alia- rumque rerum, et primus destruitur ordo, sicque in infinitum producitur. II is tor. Orient. Suppl. per Abrahamum Ecchellensum, Syrum Maronitam, cap. 7 et 8. ad calcem Chronici Oriental. Parisiis, e Typ. regia 1685. fol. Fortis fell into a singular mistake in rendering this passage, imagining that the number twenty-five referred, not to the pairs of every animal created, but to the number of new species created at one time ; and hence the doctrine of the Arabian sect appeared to coincide somewhat with his own views ; and to be consistent with his hypothesis, that man and some species of animals and plants are more modern than others. Fortis, Mem. sur 1'Hist. Jfat. de 1'Italie, vol. i. p. 202. Ch. II.] THEORY OF STRABO. 21 tic, and perhaps the abundance of sea-shells in Africa, near the Temple of Jupiter Ammon, might also be the deposit of some former inland sea, which had at length forced a passage and escaped. But Strabo rejects this theory as insufficient to account for all the phenomena, and he proposes one of his own, the pro- foundness of which modern geologists are only beginning to appreciate. < It is not/ he says, ' because the lands covered by seas were originally at different altitudes, that the waters have risen, or subsided, or receded from some parts and inun- dated others. But the reason is, that the same land is some- times raised up and sometimes depressed, and the sea also is simultaneously raised and depressed, so that it either overflows or returns into its own place again. We must therefore ascribe the cause to the ground, either to that ground which is under the sea, or to that which becomes flooded by it, but rather to that which lies beneath the sea, for this is more moveable, and, on account of its humidity, can be altered with great celerity*. It is proper,' he observes in continuation, * to derive our ex- planations from things which are obvious, and in some measure of daily occurrence, such as deluges, earthquakes, volcanic eruptions, and sudden swellings of the land beneath the sea; for the last raise up the sea also, and when the same lands subside again, they occasion the sea to be let down. And it is not merely the small, but the large islands also, and not merely the islands, but the continents, which can be lifted up together with the sea ; and both large and small tracts may subside, for habitations and cities, like Bure, Bizona, and many others^ have been engulphed by earthquakes.' In another place, this learned geographer, in alluding to the * ' Quod enim hoc attollitur aut subsidit, et vel inundat quaedam loca, vel ab iis recedit, ejus rei causa non est, quod alia aliis sola humiliora sint aut altiora; sed quod idem solum modo attollitur modo deprimitur, simulque etiam modo attolUtur modo deprimitur mare : itaque vel exundat vel in suum redit locum.' Postea, p. 88. ' Restat, ut causam adscribamus solo, sive quod mari subest sive 'quod iuundatur; potius tamen ei quod mari subest. Hoc enim multo es mobiiius et quod ob humiditatem celerius mutari possit.' Strabo, lib. ii. 22 KNOWLEDGE OF THE ANCIENTS. [Ch. II. tradition that Sicily had been separated by a convulsion from Italy, remarks, that at present the land near the sea in those parts was rarely shaken by earthquakes, since there were now open orifices whereby fire and ignited matters and waters escaped ; but formerly, when the volcanos of Etna, the Lipari Islands, Ischia, and others, were closed up, the imprisoned fire and wind might have produced far more vehement move- ments*. The doctrine, therefore, that volcanos are safety- valves, and that the subterranean convulsions are probably most violent when first the volcanic energy shifts itself to a new quarter, is not modern. We learn from a passage in Strabo f , that it was a dogma of the Gaulish Druids that the universe was immortal, but destined to survive catastrophes both of fire and water. That this doctrine was communicated to them from the East, with much of their learning, cannot be doubted. Caesar J, it will be remembered, says that they made use of Greek letters in arithmetical computations. Pliny had no theoretical opinions of his own concerning changes of the earth's surface ; and in this department, as in others, he restricted himself to the task of a compiler, without reasoning on the facts stated by him, or attempting to digest them into regular order. But his enumeration of the new islands which had been formed in the Mediterranean, and of other convulsions, shews that the ancients had not been inat- tentive observers of the changes which had taken place on the earth within the memory of man. We shall now conclude our remarks on the opinions enter- tained before the Christian era, concerning the past revolutions of our globe. No particular investigations appear to have been made for the express purpose of interpreting the monuments left by nature of ancient changes, but they were too obvious to be entirely disregarded ; and the observation of the present course of nature presented too many proofs of alterations con- tinually in progress on the earth to allow philosophers to believe * Strabo, lib. vi. p. 396. f Book iv. J 1. vi. ch. xiii. Ch. II.] KNOWLEDGE OF THE ANCIENTS. 23 that nature was in a state of rest, or that the surface had re- mained, and would continue to remain, unaltered. But they had never compared attentively the results of the destroying and reproductive operations of modern times with those of remote eras, nor had they ever entertained so much as a conjec- ture concerning the comparative antiquity of the human race, or of living species of animals and plants, with those belonging to former conditions of the organic world. They had studied the movements and positions of the heavenly bodies with labo- rious industry, and made some progress in investigating the animal, vegetable, and mineral kingdoms; but the ancient history of the globe was to them a sealed book, and, although written in characters of the most striking and imposing kind, they were unconscious even of its existence. CHAPTER III. Arabian writers of the tenth century Persecution of Omar Cosmogony of the Koran Early Italian writers Fracastoro Controversy as to the real nature of organized fossils Fossil shells attributed to the Mosaic deluge Palissy Steno Scilla Quirini Boyle Plot Hooke's Theory of Elevation by earth- quakes His speculations on lost species of animals Ray Physico-theological writers Woodward's Diluvial Theory Burnet Whiston Hutchinson Leibnitz Vallisneri Lazzaro Moro Generelli Buffon His theory con- demned by the Sorbonne as unorthodox Button's declaration Targioni Arduino Michell Catcott Raspe Fortis Testa Whitehurst Pallas Saussure. Arabian writers. AFTER the decline of the Roman empire, the cultivation of physical science was first revived with some success by the Saracens, about the middle of the eighth century of our era. The works of the most eminent classic writers were purchased at great expense from the Christians, and translated into Arabic ; and Al Mamun, son of the famous Harun-al-Rashid, the contemporary of Charlemagne, received with marks of distinction, at his court at Bagdad, astronomers and men of learning from different countries. This caliph, and some of his successors, encountered much opposition and jealousy from the doctors of the Mahomedan law, who wished the Moslems to confine their studies to the Koran, dread- ing the effects of the diffusion of a taste for the physical sciences*. Omar Cosmogony of the Koran. Almost all the works of the early Arabian writers are lost. Amongst those of the tenth century, of which fragments are now extant, is a system of mineralogy by Avicenna, a physician, in whose arrangement there is considerable merit. In the same century also, Omar, surnamed ' El Aalem,' or < the Learned,' wrote a work on ' the Retreat of the Sea.' It appears that on comparing the charts * Mod, Univ. Hist. vol. ii. chap, iv, section iii. Ch. III.] OMAR THE KORAN. 25 of his own time with those made by the Indian and Persian astronomers two thousand years before, he had satisfied him- self that important changes had taken place since the times of history in the form of the coasts of Asia, and that the extension of the sea had been greater at some former periods. He was confirmed in this opinion by the numerous salt springs and marshes in the interior of Asia, a phenomenon from which Pallas, in more recent times, has drawn the same inference. Von Hoff has suggested, with great probability, that the changes in the level of the Caspian (some of which there is reason to believe have happened within the historical era), and the geological appearances in that district, indicating the de- sertion by that sea of its ancient bed, had probably led Omar to his theory of a general subsidence. But whatever may have been the proofs relied on, his system was declared contradic- tory to certain passages in the Koran, and he was called upon publicly to recant his errors ; to avoid which persecution he went into voluntary banishment from Samarkand*. The cosmological opinions expressed in the Koran are few, and merely introduced incidentally ; so that it is not easy to understand how they could have interfered so seriously with free discussion on the former changes of the globe. The Pro- phet declared that the earth was created in two days, and the mountains were then placed on it ; and during these, and two additional days, the inhabitants of the earth were formed ; and * Von Hoff, Geschichte der Veriinderungen der Erdoberflache, vol. i. p. 406, who cites Delisle, bey Hissmann Welt-und Vb'lkergeschichte. Alte Gesch. I 1 ** Theil. s. 234. The Arabian persecutions for heretical dogmas in theology were often very sanguinary. In the same ages wherein learning was most in esteem, the Mahometans were divided into two sects, one of whom maintained that the Koran was increate, and had subsisted in the very essence of God from all eter- nity ; and the other the Motazalites, who, admitting that the Koran was instituted by God, conceived it to have been first made when revealed to the Prophet at Mecca, and accused their opponents of believing in two eternal beings. The opi . nions of each of these sects were taken up by different caliphs in succession, and the followers of each sometimes submitted to be beheaded, or flogged till at the point of death, rather than renounce their creed. Mod. Univ. Hist. vol. ii. ch. iv. 26 FRACASTORO. [Ch. III. in two more the seven heavens*. There is no more detail of circumstances ; and the deluge, which is also mentioned, is discussed with equal brevity. The waters are represented to have poured out of an oven ; A strange fable, said to be bor- rowed from the Persian Magi, who represented them as issuing from the oven of an old woman f. All men were drowned, save Noah and his family; and then God said, *O earth, swallow up thy waters ; and thou, O heaven, withhold thy rain ;' and immediately the waters abated J. We may suppose Omar to have represented the desertion of the land by the sea to have been gradual, and that his hypo- thesis required a greater lapse of ages than was consistent with Moslem orthodoxy ; for it is to be inferred from the Koran, that man and this planet were created at the same time ; and although Mahomet did not limit expressly the antiquity of the human race, yet he gave an implied sanction to the Mosaic chronology by the veneration expressed by him for the Hebrew Patriarchs . Early Italian writers Fracastoro, 1517. We must now- pass over an interval of five centuries, wherein darkness en- veloped almost every department of science, and buried in profound oblivion all prior investigations into the earth's his- tory and structure. It was not till the earlier part of the sixteenth century that geological phenomena began to attract the attention of the Christian nations. At that period a very animated controversy sprung up in Italy, concerning the true nature and origin of marine shells, and other organized fossils, found abundantly in the strata of the peninsula ||. The exca- vations made in 1517, for repairing the city of Verona, brought * Koran, chap. xli. f Sale's Koran, chap, xi., see note. { Ibid. Kossa, appointed master to the Caliph Al Mamud, was author of a book, entitled, ' The history of the Patriarchs and Prophets, from the Creation of the World: Mod. Univ. Hist., vol. ii. chap. iv. || See Brocchi's Discourse on the Progress of the Study of Fossil Conchology in Italy, where some of the following notices on Italian writers will be found more at large. Ch. III.] ANTIQUITY OF THE EARTH. 27 to light a multitude of curious petrifactions, and furnished matter for speculation to different authors, and among the rest to Fracastoro *, who declared his opinion, that fossil shells had all belonged to living animals, which had formerly lived and multiplied, where their exuviae are now found. He exposed the absurdity of having recourse to a certain f plastic force,' which it was said had power to fashion stones into organic forms ; and, with no less cogent arguments, demonstrated the futility of attributing the situation of the shells in question to the Mosaic deluge, a theory obstinately defended by some. That inundation, he observed, was too transient, it consisted principally of fluviatile waters ; and if it had transported shells to great distances, must have strewed them over the surface, not buried them at vast depths in the interior of mountains. His clear exposition of the evidence would have terminated the discussion for ever, if the passions of mankind had not been enlisted in the dispute ; and even though doubts should for a time have remained in some minds, they would speedily have been removed by the fresh information obtained almost imme- diately afterwards, respecting the structure of fossil remains, and of their living analogues. But the clear and philosophical views of Fracastoro were disregarded, and the talent and argumentative powers of the learned were doomed for three centuries to be wasted in the discussion of these two simple and preliminary questions : first, whether fossil remains had ever belonged to living creatures 5 and, secondly, whether, if this be admitted, all the phenomena could be explained by the Noachian deluge. It had been the consistent belief of the Christian world, down to the period now under consideration, that the origin of this planet was not more remote than a few thousand years ; and that since the creation the deluge was the only great catastrophe by which considerable change had been wrought on the earth's surface. On the other hand, the opinion was scarcely less general, that the final dissolution of our system was an event to be looked * Museum Calceol. 28 ANTIQUITY OF THE EARTH. [Ch. III. for at no distant period. The era, it is true, of the expected millennium had passed away ; and for five hundred years after the fatal hour, when the annihilation of the planet had been looked for, the monks remained in undisturbed enjoyment of rich grants of land bequeathed to them by pious donors, who, in the preamble of deeds beginning ' appropinquante mundi termino' * appropinquante magno judicii die,' left lasting monuments of the popular delusion *. But although in the sixteenth century it had become neces- sary to interpret the prophecies more liberally, and to assign a more distant date to the future conflagration of the world, we find, in the speculations of the early geologists, perpetual allusion to such an approaching catastrophe ; while in all that regarded the antiquity of the earth, no modification whatever of the opinions of the dark ages had been effected. Consider- able alarm was at first excited when the attempt was made to invalidate, by physical proofs, an article of faith so generally received; but there was sufficient spirit of toleration arid can- dour amongst the Italian ecclesiastics, to allow the subject to be canvassed with much freedom. They entered warmly them- selves into the controversy, often favouring different sides of the question ; and however much we may deplore the loss of time and labour devoted to the defence of untenable positions, it must be conceded, that they displayed far less polemic bit- terness than certain writers who followed them ' beyond the Alps/ two centuries and a half later. CONTROVERSY AS TO THE REAL NATURE OF FOSSIL ORGANIC REMAINS. Mattioli Falloppio. The system of scholastic disputations encouraged in the Universities of the middle ages had unfor- tunately trained men to habits of indefinite argumentation, and they often preferred absurd and extravagant propositions, * In the monasteries of Sicily, in particular, the title-deeds of many valuable grants of land are headed by such preambles, composed by the testators about the period when the good King Roger was expelling the Saracens from that island. Ch. III.] NATURE OF ORGANIZED FOSSILS. 29 because greater skill was required to maintain them ; the end and object of such intellectual combats being victory and not truth. No theory could be so far-fetched or fantastical as not to attract some followers, provided it fell in with popular notions ; and as cosmologists were not at all restricted, in building their systems, to the agency of known causes, the opponents of Fracastoro met his arguments by feigning ima- ginary causes, which differed from each other rather in name than in substance. Andrea Mattioli, for instance, an eminent botanist, the illustrator of Dioscorides, embraced the notion of Agricola, a German miner, that a certain ' materia pinguis ' or ' fatty matter/ set into fermentation by heat, gave birth to fossil organic shapes. Yet Mattioli had come to the conclu- sion, from his own observations, that porous bodies, such as bones and shells, might be converted into stone, as being per- meable to what he termed the ' lapidifying juice/ In like manner, Falloppio of Padua conceived that petrified shells had been generated by fermentation in the spots where they were found, or that they had in some cases acquired their form from { the tumultuous movements of terrestrial exhalations/ Although a celebrated professor of anatomy, he taught that certain tusks of elephants dug up in his time at Puglia were mere earthy concretions, and, consistently with these prin- ciples, he even went so far as to consider it not improbable, that the vases of Monte Testaceo at Rome were natural im- pressions stamped in the soil*. In the same spirit, Mercati, who published, in 1574, faithful figures of the fossil shells preserved by Pope Sextus V. in the Museum of the Vatican, expressed an opinion that they were mere stones, which had assumed their peculiar configuration from the influence of the heavenly bodies ; and Olivi of Cremona, who described the fossil remains of a rich Museum at Verona, was satisfied with considering them mere ' sports of nature/ Cardano, 1552. The title of a work of Cardano's, pub- lished in 1552, e De Subtilitate/ (corresponding to what would * De Fossilib., j-p. 109 and 176. 30 NATURE OF ORGANIZED FOSSILS. [Ch. III. now be called Transcendental Philosophy,) would lead us to expect, in the chapter on minerals, many far-fetched theories characteristic of that age ; but, when treating of petrified shells, he decided that they clearly indicated the former sojourn of the sea upon the mountains *. Some of the fanciful notions of those times were deemed less unreasonable, as being somewhat in harmony with the Aristotelian theory of spontaneous generation, then taught in all the schools. For men who had been instructed in early youth, that a large proportion of living animals and plants were formed from the fortuitous concourse of atoms, or had sprung from the corruption of organic matter, might easily persuade themselves, that organic shapes, often imperfectly preserved in the interior of solid rocks, owed their existence to causes equally obscure and mysterious. Cesalpino Majoli, 1597. But there were not wanting some, who at the close of this century expressed more sound and sober opinions. Cesalpino, a celebrated botanist, con- ceived that fossil shells had been left on the land by the retiring sea, and had concreted into stone during the consolidation of the soil f ; and in the following year (1597),-Simeone Majoli J went still farther, and, coinciding for the most part with the views of Cesalpino, suggested that the shells and submarine matter of the Veronese, and other districts, might have been cast up, upon the land, by volcanic explosions, like those which gave rise, in 1538, to Monte Nuovo, near Puzzuoli. This hint was the first imperfect attempt to connect the position of fossil shells with the agency of volcanos, a system afterwards more fully developed by Hooke, Lazzaro Moro, Hutton, and other writers. Two years afterwards, Imperati advocated the animal origin of fossilized shells, yet admitted that stones could vegetate by force of f an internal principle;' and, as evidence of this, he * Brocchi, Con. Foss. Subap. Disc, sui Prog., vol. i. p. 5. f De Metallic!*. t Dies Cauiculares. . PALISSY STENO. 31 referred to the teeth of fish, and spines of echini found petri- fied*. Palissy, 1580. Palissy, a French writer on < the Origin of Springs from Rain-water' and of other scientific works, under- took, in 1580, to combat the notions of many of his contempo- raries in Italy, that petrified shells had all been deposited by the universal deluge. ' He was the first, 5 said Fontenelle, when, in the French Academy, he pronounced his eulogy nearly a century and a half later, * who dared assert ' in Paris, that fossil remains of testacea and fish had once belonged to marine animals. Fabio Cclonna. To enumerate the multitude of Italian writers, who advanced various hypotheses, all equally fantas- tical, in the early part of the seventeeth century, would be un- profitably tedious, but Fabio Colonna deserves to be distin- guished ; for, although he gave way to the dogma, that all fossil remains were to be referred to the Noachian deluge, he resisted the absurd theory of Stelluti, who taught that fossil wood and ammonites were mere clay, altered into such forms by sulphureous waters and subterranean heat ; and he pointed out the different states of shells buried in the strata, distin- guishing between, first, the mere mould or impression ; secondly, the cast or nucleus ; and thirdly, the remains of the shell itself. He had also the merit of being the first to point out, that some of the fossils had belonged to marine, and some to terrestrial testacea [. Steno, 1669. But the most remarkable work of that period was published by Steno, a Dane, once professor of anatomy at Padua, and who afterwards resided many years at the court of the Grand Duke of Tuscany. The treatise bears the quajpit title of ' De Solido intra Solidum contento naturaliter, (1669,)' by which the author intended to express 6 On Gems, Crystals, and organic Petrifactions inclosed within solid Rocks.' This work attests the priority of the Italian school in geological research; exemplifying at the same time the powerful obstacles * Storia Naturale. f Osserv, sugli Animali aquat, e terrest. 1626. 32 STENO. [Ch. III. opposed, in that age, to the general reception of enlarged views in the science. Steno had compared the fossil shells with their recent analogues, and traced the various gradations from the state of mere calcination, when their natural gluten only was lost, to the perfect substitution of stony matter. He demon- strated that many fossil teeth found in Tuscany belonged to a species of shark ; and he dissected, for the purpose of com- parison, one of these fish recently taken from the Mediter- ranean. That the remains of shells and marine animals found petrified were not of animal origin was still a favourite dogma of many, who were unwilling to believe that the earth could have been inhabited by living beings long before many of the mountains were formed. By way of compromise, as it were, for dissenting from this opinion, Steno conceded, as Fabio Colonna had done before him, that all marine fossils might have been transported into their present situation at the time of the Noachian deluge. He maintained that fossil vegetables had been once living plants, and he hinted that they might, in some instances, indicate the distinction between fluviatile and marine deposits. He also inferred that the present mountains had not existed ever since the origin of things, suggesting that many strata of submarine origin had been accumulated in the interval between the crea- tion and deluge. Here he displayed his great anxiety to re- concile his theory with the Scriptures ; for he at the same time advanced an opinion, which does not seem very consistent with such a doctrine, viz. that there was a wide distinction between the shelly, and nearly horizontal beds at the foot of the Apen- nines, and the older mountains of highly inclined stratifica- tion. Both, he observed, were of sedimentary origin ; and a considerable interval of time must have separated their forma- tion. Tuscany, according to him, had successively passed throuyh six different states ; and to explain these mighty changes, he called in the agency of inundations, earthquakes, and subterranean fires. His generalizations were for the most part comprehensive Ch. III.] SCILLA DILUVIAL THEORY. 33 and just ; but such was his awe of popular prejudice, that he only ventured to throw them out as mere conjectures, and the timid reserve of his expressions must have raised doubts as to his own confidence in his opinions, and deprived them of some of the authority due to them. Scilla, 1670. Scilla, a Sicilian painter, published, in 1670, a work on the fossils of Calabria, illustrated by good engrav- ings. This was written in Latin, with great spirit and ele- gance, and it proves the continued ascendency of dogmas often refuted; for we find the wit and eloquence of the author chiefly directed against the obstinate incredulity of naturalists, as to the organic nature of fossil shells *. Like many eminent naturalists of his day, Scilla gave way to the popular persua- sion, that all fossil shells were the effects and proofs of the Mosaic deluge. It may be doubted whether he was perfectly sincere, and some of his contemporaries who took the same course were certainly not so. But so eager were they to root out what they justly considered an absurd prejudice respecting the nature of organized fossils, that they seem to have been ready to make any concessions, in order to establish this preli- minary point. Such a compromising policy was short- sigh ted, since it was to little purpose that the nature of the documents should at length be correctly understood, if men were to be prevented from deducing fair conclusions from them. Diluvial Theory. The theologians who now entered the field in Italy, Germany, France and England, were innumer- able; and henceforward, they who refused to subscribe to the position, that all marine organic remains were proofs of the Mosaic deluge, were exposed to the imputation of disbelieving the whole of the sacred writings. Scarcely any step had been made in approximating to sound theories since the time of * Scilla quotes the remark of Cicero on the story that a stone in Chios had been cleft open, and presented the head of Paniscus in relief * I believe,' said the orator, l that the figure bore some resemblance to Paniscus, but not such that you would have deemed it sculptured by Scopas, for chance never perfectly imitates the truth.' VOL. I. D 34 DILUVIAL THEORY. [Ch. III. Fracastoro, more than a hundred years having been lost, in writing down the dogma that organized fossils were mere sports of nature. An additional period of a century and a half was now destined to be consumed in exploding the hypothesis, that organized fossils had all been buried in the solid strata by the Noachian flood. Never did a theoretical fallacy, in any branch of science, interfere more seriously with accurate ob- servation and the systematic classification of facts. In recent times, we may attribute our rapid progress chiefly to the care- ful determination of the order of succession in mineral masses, by means of their different organic contents, and their regular superposition. But the old diluvialists were induced by their system to confound all the groups of strata together instead of discriminating, to refer all appearances to one cause and to one brief period, not to a variety of causes acting throughout a long succession of epochs. They saw the phenomena only as they desired to see them, sometimes misrepresenting facts, and at other times deducing false conclusions from correct data. Under the influence of such prejudices, three centuries were of as little avail, as a few years in our own times, when we are no longer required to propel the vessel against the force of an adverse current. It may be well to forewarn our readers, that in tracing the history of geology from the close of the seventeenth to the end of the eighteenth century, they must expect to be occupied with accounts of the retardation, as well as of the advance of the science. It will be our irksome task to point out the fre- quent revival of exploded errors, and the relapse from sound to the most absurd opinions. It will be necessary to dwell on futile reasoning and visionary hypothesis, because the most extrava- gant systems were often invented or controverted by men of acknowledged talent. A sketch of the progress of Geology is the history of a constant and violent struggle between new opinions and ancient doctrines, sanctioned by the implicit faith of many generations, and supposed to rest on scriptural autho- rity. The inquiry, therefore, although highly interesting to Ch. III.] QUIRINI PLOT LISTER. 35 one who studies the philosophy of the human mind, is singu- larly barren of instruction to him who searches for truths in physical science. Quirini, 1676. Quirini, in 1676*, contended, in opposition to Scilla, that the diluvian waters could not have conveyed heavy bodies to the summit of mountains, since the agitation of the sea never (as Boyle had demonstrated) extended to great depthsf, and still less could the testacea, as some pre- tended, have lived in these diluvian waters, for 'the duration of the flood was brief, and the heavy rains must have destroyed the saltness of the sea /' He was the first writer who ventured to maintain that the universality of the Noachian cataclysm ought not to be insisted upon. As to the nature of petrified shells, he conceived that as earthy particles united in the sea to form the shells of mollusca, the same crystallizing process might be effected on the land, and that, in the latter case, the germs of the animals might have been disseminated through the substance of the rocks, and afterwards developed by virtue of humidity. Visionary as was this doctrine, it gained many proselytes even amongst the more sober reasoners of Italy and Germany, for it conceded both that fossil bodies were organic, and that the diluvial theory could not account for them. Plot Lister, 1678. In the mean time, the doctrine that fossil shells had never belonged to real animals, maintained its ground in England, where the agitation of the question began at a much later period. Dr. Plot, in his c Natural His- tory of Oxfordshire/ (1677,) attributed to a ' plastic virtue * De Testaceis fossilibus Mus. Septaliani. f The opinions of Boyle, alluded to by Quirini, were published a few years before, in a short article entitled ' On the bottom of the Sea.' From observations collected from the divers of the pearl fishery, Boyle inferred that when the waves were six or seven feet high above the surface of the water, there were no signs of agitation at the depth of fifteen fathoms ; and that even during heavy gales of wind, the motion of the water was exceedingly diminished at the depth of twelve or fifteen feet. He had also learnt from some of his informants, that there were currents running in opposite directions at different depths. Boyle's Works, vol. iii. p. 1 1 0. London, 1 744. D 2 36 LISTER HOOKE, [Ch. III. latent in the earth ' the origin of fossil shells and fishes ; and Lister, to his accurate account of British shells, in 1678, added the fossil species, under the appellation of turbinated and bivalve stones. Either,' said he, < these were terriginous, or, if otherwise, the animals they so exactly represent have become extinct.' This writer appears to have been the first who was aware of the continuity over large districts of the principal groups of strata in the British series, and who proposed the construction of regular geological maps*. Hooke, 1688. The < Posthumous Works of Robert Hooke, M.D., 1 well known as a great mathematician and natural phi- losopher, appeared in 1705, containing, ' A Discourse of Earthquakes,' which, we are informed by his editor, was writ- ten in 1668, but revised at subsequent periods f. Hooke frequently refers to the best Italian and English authors who wrote before his time on geological subjects ; but there are no passages in his works implying that he participated in the en- larged views of Steno and Lister, or of his contemporary, Woodward, in regard to the geographical extent of certain groups of strata. His treatise, however, is the most philoso- phical production of that age, in regard to the causes of former changes in the organic and inorganic kingdoms of nature. * However trivial a thing,' he says, ' a rotten shell may appear to some, yet these monuments of nature are more cer- tain tokens of antiquity than coins or medals, since the best- of those may be counterfeited or made by art and design, as may also books, manuscripts, and inscriptions, as all the learned are now sufficiently satisfied has often been actually practised,' Sec. ; ' and though it must be granted that it is very difficult to read them (the records of nature) and to raise a chronology out of them, and to state the intervals of the time wherein such or * See Mr. Conybeare's excellent Introduction to the ' Outlines of the Geology of England and Wales,' p. 12. f Between the year 1688 and his death, in 1703, he read several memoirs to the Royal Society, and delivered lectures on various subjects, relating to fossil remains and the effects of earthquakes. I Ch. III.] HOOKE ON EXTINCT SPECIES. 37 such catastrophes and mutations have happened, yet it is not impossible*.' His theory of the extinction of Species. Respecting the ex- tinction of species, Hooke was aware that the fossil ammonites, nautili, and many other shells and fossil skeletons found in England, were of different species from any then known ; but he doubted whether the species had become extinct, observing that the knowledge of naturalists of all the marine species, especially those inhabiting the deep sea, was very deficient. In some parts of his writings, however, he leans to the opinion that species had been lost ; and, in speculating on this subject, he even suggests that there might be some connexion between the disappearance of certain kinds of animals and plants, and the changes wrought by earthquakes in former ages. Some species, he observes with great sagacity, are e peculiar to certain places, and not to be found elsewhere. If, then, such a place had been swallowed up, it is not improbable but that those animate beings may have been destroyed with it ; and this may be true both of aerial and aquatic animals : for those animated bodies, whether vegetables or animals, which were naturally nourished or refreshed by the air, would be destroyed by the water f,' &c. Turtles, he adds, and such large ammonites as are found in Portland, seem to have been the productions of the seas of hotter countries, and it is necessary to suppose that England once lay under the sea within the torrid zone ! To explain this and similar phenomena, he indulges in a variety of speculations concerning changes in the position of the axis of the earth's rotation, a shifting of the earth's centre of gravity, ' analogous to the revolutions of the magnetic pole? &c. None of these conjectures, however, are proposed dogmatically, but rather in the hope of promoting fresh inquiries and experi- ments. In opposition to the prejudices of his age, we find him argu- ing that nature had not formed fossil bodies ' for no other end * Posth. \Vorks, Lecture Feb. 29, 1688. t Posth. Works, p. 327. 38 IIOOKE ON EARTHQUAKES. [Ch. III. than to play the mimic in the mineral kingdom' that figured stones were ' really the several bodies they represent, or the mouldings of them petrified/ and 'not, as some have imagined, a " lusus naturae," sporting herself in the needless formation of useless beings *.' It was objected to Hooke, that his doctrine of the extinction of species derogated from the wisdom and power of the Omni- potent Creator; but he answered, that, as individuals die, there may be some termination to the duration of a species ; and his opinions, he declared, were not repugnant to Holy Writ : for the Scriptures taught that our system was degene- rating, and tending to its final dissolution ; ' and as, when that shall happen, all the species will be lost, why not some at one time and some at another \ ? ' His theory of the effects of earthquakes. But his principal object was to account for the manner in which shells had been conveyed into the higher parts of < the Alps, Apennines, and Pyrenean hills, and the interior of continents in general/ These and other appearances, he said, might have been brought about by earthquakes, which have turned plains into mountains, and mountains into plains, seas into land, and land into seas, made rivers where there were none before, and swallowed up * Posth. Works, Lecture Feb. 15, 1688. Hooke explained, with considerable clearness, the different modes wherein organic substances may become lapidified j and, among other illustrations, he mentions some silicified palm-wood brought from Africa, on which M. de la Hire had read a Memoir to the Royal Academy of France, (June, 1692,) wherein he had pointed out not only the tubes running the length of the trunk, but the roots at one extremity. De la Hire, says Hooke, also treated of certain trees found petrified in < the river that passes by Bakan, in the kingdom of Ava, and which has for the space of ten leagues the virtue of petrify- ing wood.' It is an interesting fact, that the silicified wood of the Irawadi should have attracted attention more than one hundred years ago. Remarkable dis- coveries have been recently made there of fossil animals and vegetables by Mr. Crawfurd and Dr. Wallich. See Geol. Trans., vol. ii. part iii. p. 377, Second Series. De la Hire cites Father Duchatz, in the second volume of < Observations made in the Indies by the Jesuits.' t Posth. Works, Lecture May 29, 1689. Ch. III.] HOOKERS DILUVIAL THEORY. 39 others that formerly were, &c. &c. ; and which , since the crea- tion of the world, have wrought many great changes on the superficial parts of the earth, and have been the instruments of placing shells, bones, plants, fishes, and the like, in those places, where, with much astonishment, we find them*.' This doctrine, it is true, had been laid down in terms almost equally explicit by Strabo, to explain the occurrence of fossil shells in the interior of continents, and to that geographer, and other writers of antiquity, Hooke frequently refers ; but the revival and development of the system was an important step in the progress of modern science. Hooke enumerated all the examples known to him of sub- terranean disturbance, from ' the sad catastrophe of Sodom and Gomorrah ' down to the Chilian earthquake of 1646. The elevating of the bottom of the sea, the sinking and submersion of the land, and most of the inequalities of the earth's surface, might, he said, be accounted for by the agency of these sub- terranean causes. He mentions that the coast near Naples was raised during the eruption of Monte Nuovo ; and that, in 1591, land rose in the island of St. Michael, during an erup- tion ; and although it would be more difficult, he says, to prove, he does not doubt but that there had been as many earthquakes in the parts of the earth under the ocean, as in the parts of the dry land ; in confirmation of which he men- tions the immeasurable depth of the sea near some volcanos. To attest the extent of simultaneous subterranean movements, he refers to an earthquake in the West Indies, in 1690, where the space of earth raised, or ' struck upwards' by the shock, exceeded the length of the Alps and the Pyrenees. Hooke' s diluvial theory. As Hooke declared the favourite hypothesis of the day (* that marine fossil bodies were to be referred to Noah's flood ') to be wholly untenable, he appears to have felt himself called upon to substitute a diluvial theory of his own, and thus he became involved in countless difficul- ties and contradictions. ' During the great catastrophe, 1 he * Posth. Works, p. 312. 40 HOOKE RAY. [Ch. III. said, < there might have been a changing of that part which was before dry land into sea by sinking, and of that which was sea into dry land by raising, and marine bodies might have been buried in sediment beneath the ocean, in the interval between the creation and the deluge*.' Then followed a dis- quisition on the separation of the land from the waters, men- tioned in Genesis : during which operation some places of the shell of the earth were forced outwards, and others pressed downwards or inwards, &c. His diluvial hypothesis very much resembled that of Steno, and was entirely opposed to the fundamental principles professed by him, that he would ex- plain the former changes of the earth in a more natural manner than others had done. When, in despite of this declaration, he required a former ' crisis of nature/ and taught that earth- quakes had become debilitated, and that the Alps, Andes, and other chains, had been lifted up in a few months, his machinery was as extravagant and visionary as that of his most fanciful predecessors ; and for this reason, perhaps, his whole theory of earthquakes met with undeserved neglect. Ray, 1692, One of his contemporaries, the celebrated na- turalist, Ray, participated in the same desire to explain geolo- gical phenomena, by reference to causes less hypothetical than those usually resorted tof. In his Essay on 'Chaos and Creation/ he proposed a system, agreeing in its outline, and in many of its details, with that of Hooke ; but his knowledge of natural history enabled him to elucidate the subject with various original observations. Earthquakes, he suggested, might have been the second causes employed at the creation, in separating the land from the waters, and in gathering the waters together into one place. He mentions, like Hooke, the earthquake of 1646, which had violently shaken the Andes for * Posth. Works, p. 410. f Ray's Physico-theological Discourses were of somewhat later date than Hooke's great work on earthquakes. He speaks of Hooke as one < whom for his learning and deep insight into the mysteries of nature he deservedly honoured.' On the Deluge, chap, iv, .. RAY WOODWARD. 41 some hundreds of leagues, and made many alterations therein. In assigning a cause for the general deluge, he preferred a change in the earth's centre of gravity to the introduction of earthquakes. Some unknown cause, he said, might have forced the subterranean waters outwards, as was, perhaps, indicated by ' the breaking up of the fountains of the great deep.' Ray was one of the first of our writers who enlarged upon the effects of running water upon the land, and of the en- croachment of the sea upon the shores. So important did he consider the agency of these causes, that he saw in them an indication of the tendency of our system to its final dissolution ; and he wondered why the earth did not proceed more rapidly towards a general submersion beneath the sea, when so much matter was carried down by rivers, or undermined in the sea- cliffs. We perceive clearly from his writings, that the gradual decline of our system, and its future consummation by-fire, was held to be as necessary an article of faith by the orthodox, as was the recent origin of our planet. His Discourses, like those of Hooke, are highly interesting, as attesting the familiar association in the minds of philosophers, in the age of Newton, of questions in physics and divinity. Ray gave an unequivo- cal proof of the sincerity of his mind, by sacrificing his prefer- ment in the church, rather than take an oath against the Covenanters, which he could not reconcile with his conscience. His reputation, moreover, in the scientific world placed him high above the temptation of courting popularity, by pandering to the physico- theological taste of his age. It is, therefore, curious to meet with so many citations from the Christian fathers and prophets in his essays on physical science to find him in one page proceeding, by the strict rules of induction, to explain the former changes of the globe, and in the next gravely entertaining the question, whether the sun and stars, and the whole heavens shall be annihilated, together with the earth, at the era of the grand conflagration. Woodward, 1695. Among the contemporaries of Hooke 42 WOODWARD BURNET. [Ch. III. and Ray, Woodward, a professor of medicine, had acquired the most extensive information respecting the geological struc- ture of the crust of the earth. He had examined many parts of the British strata with minute attention ; and his systematic collection of specimens, bequeathed to the University of Cam- bridge, and still preserved there as arranged by him, shows how far he had advanced in ascertaining the order of superpo- sition. From the great number of facts collected by him, we might have expected his theoretical views to be more sound and enlarged than those of his contemporaries ; but in his anxiety to accommodate all observed phenomena to the scrip- tural account of the Creation and Deluge, he arrived at most erroneous results. He conceived < the whole terrestrial globe to have been taken to pieces and dissolved at the flood, and the strata to have settled down from this promiscuous mass as any earthy sediment from a fluid *.' In corroboration of these views, he insisted upon the fact, that marine bodies are lodged in the strata according to the order of their gravity, the heavier shells in stone, the lighter in chalk, and so of the rest f.' Ray immediately exposed the unfounded nature of this assertion, remarking truly, that fossil bodies ' are often mingled, heavy with light, in the same stratum ;' and he even went so far as to say, that Woodward ' must have invented the phenomena for the sake of confirming his bold and strange hypothesis J ' a strong expression from the pen of a contemporary. Burnet, 1690. At the same time Burnet published his < Theory of the Earth .' The title is most characteristic of the age, SECONDARY ROCKS. 115 Proofs from analogy of extinct species. If we pass from the consideration of these more modern deposits, whether of marine or continental origin, in which existing species are intermixed with the extinct, to strata of somewhat higher anti- quity (older tertiary strata, calcaire grossier, London clay, freshwater formations of Paris and Isle of Wight, &c.), we can only reason from analogy, since the species, whether of mammalia, reptiles, or testacea, are scarcely in any instance identifiable with any now in being *. In these strata, whether they were formed in seas or lakes, we find the remains of many animals analogous to those of hot climates, such as the croco- dile, turtle, and tortoise, together with many large shells of the genus nautilus, and plants indicating such a temperature as is now found along the borders of the Mediterranean. A great interval of time appears to have elapsed between the deposition of the last-mentioned (tertiary) strata, and the secondary formations, which constitute the principal portion of the more elevated land in Europe. In these secondary rocks a very distinct assemblage of organized fossils are en- tombed, all of unknown species, and many of them referrible to genera and families now most abundant between the tropics. Among the most remarkable are many gigantic reptiles, some of them herbivorous, others carnivorous, and far exceeding in size any now known even in the torrid zone. The genera are for the most part extinct, but some of them, as the crocodile and monitor, have still representatives in the warmer parts of the earth. Coral reefs also were evidently numerous in the seas of the same period, and composed of species belonging to genera now characteristic of a tropical climate. The number * In the London clay, I believe, no recent species are yet discovered. But of twelve hundred species of shells, collected from the different fresh-water and ma- rine formations of the Paris basin, M. Deshayes informs me, that there are some, but not much exceeding the proportion of three in a hundred, which he regards as perfectly identical with living species. Among these are Melanopsis buccinoides, from Epernais, now living in the Grecian archipelago, and Melania inquinata, now found between the tropics in the Philippine islands. Venus divaricata is not uncommon in the calcaire grossier at Grignon, 12 116 FOSSIL COAL-PLANTS. [Ch. VI. of immense chambered shells also leads us to infer an elevated temperature ; and the associated fossil plants, although imper- fectly known, tend to the same conclusion, the Cycadese con- stituting the most numerous family. But the study of the fossil flora of the coal deposits of still higher antiquity has yielded the most extraordinary evidence of an extremely hot climate, for it consisted almost exclusively of large vascular cryptogamic plants. We learn, from the labours of M. Ad. Brongniart, that there existed at that epoch Equiseta upwards of ten feet high, and from five to six inches in diameter; tree ferns of from forty to fifty feet in height, and arborescent Lycopodiaceae, of from sixty to seventy feet high*. Of the above classes of vegetables, the species are all small at present in cold climates ; while in tropical regions there occur, together with small species, many of a much greater size, but their development at present, even in the hottest parts of the globe, is inferior to that indicated by the petrified forms of the coal formation. An elevated and uniform temperature, and great humidity in the air, are the causes most favourable for the numerical pre- dominance and the great size of these plants within the torrid zone at present f. * Consid. Generates sur la Nature de la Vegetation, &c. Ann. des Sci. Nat. Nov. 1828. f Humboldt, in speaking of the vegetation of the present era, considers the laws which govern the distribution of vegetable forms to be sufficiently constant to enable a botanist, who is informed of the number of one class of plants, to con- jecture with tolerable accuracy the relative number of all others. It is premature, perhaps, to apply this law of proportion to the fossil botany of strata, between the coal formation and the chalk, as M. Adolphe Brongniart has attempted, as the number of species hitherto procured is so inconsiderable, that the quotient would be materially altered by the addition of one or two species. It may also be ob- jected, that the fossil flora consists of such plants as may accidentally have been floated into seas, lakes, or estuaries, and may often, perhaps always, give a false representation of the numerical relations of families then living on the land. Yet, after allowing for all liability to error on these grounds, the argument founded on the comparative numbers of the fossil plants of the carboniferous strata is very strong. Martins informs us that, on seeing the tesselated surface of the stems of arbp* Ch.VI.] FOSSIL COAL PLANTS. H7 If the gigantic size and form of these fossil plants are remarkable, still more so is the extent of their geographical distribution ; for impressions of arborescent ferns, such as cha- racterize our English carboniferous strata, have been brought from Melville island, in latitude 75. * The corals and cham- bered shells, which occur in beds interstratified with the coal (as in mountain limestone), afford also indications of a warm climate, the gigantic orthocerata of this era being, to recent multilocular shells, what the fossil ferns, equiseta, and other plants of the coal strata, are in comparison with plants now growing within the tropics. These shells also, like the vege- table impressions, have been brought from rocks in very high latitudes in North America. In vain should we attempt to explain away the phenomena of the carboniferous and other secondary formations, by sup- posing that the plants were drifted from equatorial seas. During the accumulation and consolidation of so many sedi- mentary deposits, and the various movements and dislocations to which they were subjected at different periods, rivers and currents must often have changed their direction, and wood might as often be floated from the arctic towards tropical seas, as in an opposite direction. It is undeniable, that the mate- rials for future beds of lignite and coal are now amassed in high latitudes far from the districts where the forests grew, and on shores where scarcely a stunted shrub can now exist. The Mackenzie, and other rivers of North America, carry pines with their roots attached for many hundred miles towards the north, into the arctic sea, where they are imbedded in deltas, and some of them drifted still farther, by currents towards the pole. But such agency, although it might account for some partial anomalies in the admixture of vegetable re- mains of different climes, can by no means weaken the argu- rescent ferns in Brazil, he was reminded of their prototypes in the impressions which he had seen in the coal-mines of Germany. * Mr. Konig's description of the rocks brought home by Captain Parry, Journ, of Science, vol. xv. p. 20. 118 FOSSIL COAL-PLANTS. [Ch.VI. ments deduced from the general character of fossil vegetable remains. We cannot suppose the leaves of tree ferns to be transported by water for thousands of miles, without being injured ; nor, if this were possible, would the same hypothesis explain the presence of uninjured corals and multilocular shells of con- temporary origin, for these must have lived in the same lati- tudes where they are now inclosed in rocks. The plants, moreover, whose remains have given rise to the coal beds, must be supposed to have grown upon the same land, the destruction of which provided materials for the sandstones and conglomerates of that group of strata. The coarseness of the particles of many of these rocks attests that they were not borne from very remote localities, but were most probably derived from islands in a vast sea, which was continuous, at that time, over a great part of the northern hemisphere, as is demonstrated by the great extent of the mountain and tran- sition limestone formations. The same observation is applicable to many secondary strata of a later epoch. There must have been dry land in these latitudes, to provide materials by its disintegration for sand- stones, to afford a beach whereon the oviparous reptiles de- posited their eggs, to furnish an habitation for the opossum of Stonesfield, and the insects of Solenhofen. The vegetation of the same lands, therefore, must in general have imparted to fossil floras their prevailing character. From the considerations above enumerated, we must infer, that the remains both of the animal and vegetable kingdom preserved in strata of different ages, indicate that there has been a great diminution of temperature throughout the north- ern hemisphere, in the latitudes now occupied by Europe, Asia, and America. The change has extended to the arctic circle, as well as to the temperate zone. The heat and humi- dity of the air, and the uniformity of climate, appear to have been most remarkable when the oldest strata hitherto disco- vered were formed. The approximation to a climate similar Ch. VI.] CHANGE OF CLIMATE. 119 to that now enjoyed in these latitudes,, does not commence till the era of the formations termed tertiary, and while the differ- ent tertiary rocks were deposited in succession, the temperature seems to have been still further lowered, and to have continued to diminish gradually, even after the appearance of a great portion of existing species upon the earth. CHAPTER VII. Further examination of the question as to the discordance of the ancient and modern causes of change On the causes of vicissitudes in climate Remarks on the present diffusion of heat over the globe On the dependence of the mean temperature on the relative position of land and sea Isothermal lines Cur- rents from equatorial regions Drifting of icebergs Different temperature of Northern and Southern hemispheres Combination of causes which might produce the extreme cold of which the earth's surface is susceptible On the conditions necessary for the production of the extreme of heat, and its probable effects on organic life. Causes of vicissitudes in climate. As the proofs enumerated in the last chapter indicate that the earth's surface has expe- rienced great changes of climate since the deposition of the older sedimentary strata, we have next to inquire, how such vicissitudes can be reconciled with the existing order of nature. The cosmogonist has availed himself of this, as of every ob- scure problem in geology, to confirm his views concerning a period when the laws of the animate and inanimate world were wholly distinct from those now established ; and he has in this, as in all other cases, succeeded so far, as to divert attention from that class of facts, which, if fully understood, might pro- bably lead to an explanation of the phenomenon. At first, it was imagined that the earth's axis had been for ages perpen- dicular to the plane of the ecliptic, so that there was a per- petual equinox, and unity of seasons throughout the year ; that the planet enjoyed this 'paradisiacal ' state until the era of the great flood ; but in that catastrophe, whether by the shock of a comet, or some other convulsion, it lost its equal poise, and hence the obliquity of its axis, and with that the varied seasons of the temperate zone, and the long nights and days of the polar circles. When the advancement of astronomical science had ex- ploded this theory, it was assumed, that the earth at its creation was in a state of fluidity, and red hot, and that ever Ch. VII.] LAWS GOVERNING THE DIFFUSION OF HEAT. 121 since that era it had been cooling down, contracting its dimen- sions, and acquiring a solid crust, an hypothesis equally arbitrary, but more calculated for lasting popularity, because, by referring the mind directly to the beginning of things, it requires no support from observation, nor from any ulterior hypothesis. They who are satisfied with this solution are relieved from all necessity of inquiry into the present laws which regulate the diffusion of heat over the surface, for how- ever well these may be ascertained, they cannot possibly afford a full and exact elucidation of the internal changes of an embryo world. As well might a naturalist, by merely study- ing the plumage and external forms of full-fledged birds, hope to divine the colour of their eggs, or the mysterious meta- morphoses of the yolk during incubation. But if, instead of vague conjectures as to what might have been the state of the planet at the era of its creation, we fix our thoughts steadily on the connexion at present between climate and the distribution of land and sea ; and if we then consider what influence former fluctuations in the physical geography of the earth must have had on superficial temperature, we may perhaps approximate to a true theory. If doubt still remain, it should be ascribed to our ignorance of the laws of Nature, not to revolutions in her economy ; it should stimulate us to further research, not tempt us to indulge our fancies in framing imaginary systems for the government of infant worlds. Laws governing the diffusion of heat over the globe. In con- sidering the laws which regulate the diffusion of heat over the globe, says Humboldt, we must beware not to regard the climate of Europe as a type of the temperature which all coun- tries placed under the same latitudes enjoy. The physical sciences, observes this philosopher, always bear the impress of the places where they began to be cultivated ; and, as in geo- logy, an attempt was at first made to refer all the volcanic phenomena to those of the volcanos in Italy, so in meteorology, a small part of the old world, the centre of the primitive civili- sation of Europe, was for a long time considered a type to which 122 DEPENDENCE OF CLIMATE [Ch. VII. the climate of all corresponding latitudes might be referred. But this region, constituting only one-seventh of the whole globe, proved eventually to be the exception to the general rule ; and for the same reason we may warn the geologist to be on his guard, and not hastily to assume that the temperature of the earth in the present era is a type of that which most usually obtains, since he contemplates far mightier alterations in the position of land and sea, at different epochs, than those which now cause the climate of Europe to differ from that of other countries in the same parallels. It is now well ascertained that zones of equal warmth, both in the atmosphere and in the waters of the ocean, are neither parallel to the equator nor to each other*. It is also dis- covered that the same mean annual temperature may exist in two places which enjoy very different climates, for the seasons may be nearly equalized or violently contrasted. Thus the lines of equal winter temperature do not coincide with the lines of equal annual heat, or isothermal lines. The deviations of all these lines from the same parallel of latitude, are determined by a multitude of circumstances, among the principal of which are the position, direction, and elevation of the continents and islands, the position and depth of the sea, and the direction of currents and of winds. It is necessary to go northwards in Europe in order to find the same mean quantity of annual heat as in a similar latitude in North America. On comparing these two continents, it is found that places situated in the same latitudes, have sometimes a mean difference of temperature amounting to 11, or even sometimes 17, of Fahrenheit ; and places on the two continents, which have the same mean temperature, have sometimes a dif- * We are indebted to Baron Alex. Humboldt for collecting together, in a beau- tiful essay, the scattered data on which some approximation to a true theory of the distribution of heat over the globe may be founded. Many of these data are de- rived from the author's own observations, and many from the works of M. Prevost on the radiation of heat, and other writers. See Humboldt on Isothermal Lines, Memoires d'Arcueil, torn, iii., translated in the Edin. Phil. Journ., vol. iii. July, 1820. Ch. VII,] ON THE POSITION OF LAND AND SEA. 123 ference in latitude of from 7 to 13.* The principal cause of greater intensity of cold in corresponding latitudes of North America and Europe, is the connexion of the former country with the polar circle, by a large tract of land, some of which is from three to five thousand feet in height, and, on the other hand, the separation of Europe from the arctic circle by an ocean. The ocean has a tendency to preserve every where a mean temperature, which it communicates to the contiguous land., so that it tempers the climate, moderating alike an excess of heat or cold. The elevated land, on the other hand,, rising to the colder regions of the atmosphere, becomes a great reser- voir of ice and snow, attracts, condenses, and congeals vapour, and communicates its cold to the adjoining country. For this reason, Greenland, forming part of a continent which stretches northward to the 82d degree of latitude, experiences under the 60th parallel a more rigorous climate than Lapland under the 72d parallel. But if land be situated between the 40th parallel and the equator, it produces, unless it be of extreme height, exactly the opposite effect, for it then warms the tracts of land or sea that intervene between it and the polar circle. For the surface being in this case exposed to the vertical, or nearly vertical rays of the sun, absorbs a large quantity of heat, which it diffuses by radiation into the atmosphere. For this reason, the western parts of the old continent derive warmth from Africa, ( which, like an immense furnace,' says Malte-Brun f , ' distributes its heat to Arabia, to Turkey in Asia, and to Europe.' On the contrary, Asia, in its north-eastern extremity, experiences in the same latitude extreme cold, for it has land on the north between the 60th and 70th parallel, while to the south it is separated from the equator by the North Pacific. In consequence of the more equal temperature of the waters of the ocean, the climate of islands and coasts differs essentially from that of the interior of continents, the former being cha- * Humboldt's tables, Essay on Isothermal Lines, &c. t Phys. Geog., book xvii. 124 GULF STREAM. [Ch. VII. racterized by mild winters and more temperate summers ; for the sea breezes moderate the cold of winter, as well as the sum- mer heat. When, therefore, we trace round the globe those belts in which the mean annual temperature is the same, we often find great differences in climate ; for there are insular climates where the seasons are nearly equalized, and excessive climates, as they have been termed, where the temperature of winter and summer is strongly contrasted. The whole of Europe, compared with the eastern parts of America and Asia, has an insular climate. The northern part of China, and the Atlantic region of the United States, exhibit ' excessive cli- mates.' We find at New York, says Humboldt, the summer of Rome and the winter of Copenhagen ; at Quebec, the sum- mer of Paris and the winter of Petersburgh. At Pekin, in China, where the mean temperature of the year is that of the coasts of Brittany, the scorching heats of summer are greater than at Cairo, and the winters as rigorous as at Upsal*. If lines be drawn round the globe through all those places which have the same winter temperature, they are found to deviate from the terrestrial parallels much farther than the lines of equal mean annual heat. For the lines of equal winter in Europe are often curved so as to reach parallels of latitude 9 or 10 distant from each other, whereas the isothermal lines only differ from 4 to 5. Influence of currents on temperature. Among other influen- tial causes, both of remarkable diversity in the mean annual heat, and of unequal division of heat in the different seasons, are the direction of currents and the accumulation and drifting of ice in high latitudes. That most powerful current, the Gulf stream, after doubling the Cape of Good Hope, flows to the northward along the western coast of Africa, then crosses the Atlantic, and accumulates in the Gulf of Mexico. It then issues through the Straits of Bahama, running northwards at the rate of four miles an hour, and retains in the parallel of * On Isothermal Lines. Ch. VII.] INFLUENCE OF CURRENTS ON TEMPERATURE. 125 38, nearly one thousand miles from the above strait, a tempe- rature 10 Fahrenheit warmer than the air. The general climate of Europe is materially affected by the volume of warmer water thus borne northwards, for it main- tains an open sea free from ice in the meridian of East Green- land and Spitzbergen, and thus moderates the cold of all the lands lying to the south. Until the waters of the great cur- rent reach the circumpolar sea, their specific gravity is less than that of the lower strata of water ; but when they arrive near Spitzbergen, they meet with the water of melted ice which is still lighter, for it is a well-known law of this fluid, that it passes the point of greatest density when cooled down below 40, and between that and the freezing point expands again. The warmer current, therefore, being now the heavier, sinks below the surface, so that in the lower regions it is found to be from 16 to 20 Fahrenheit, above the mean temperature of the climate. The movements of the sea, however, cause this under- current sometimes to appear at the surface, and greatly to moderate the cold *. The great glaciers generated in the valleys of Spitzbergen, in the 79 of north latitude, are almost all cut off at the beach, being melted by the feeble remnant of heat retained by the Gulf stream. In Baffin's Bay, on the contrary, on the east coast of Old Greenland, where the temperature of the sea is not mitigated by the same cause, and where there is no warmer under-current, the glaciers stretch out from the shore, and fur- nish repeated crops of mountainous masses of ice which float off into the ocean f . The number and dimensions of these bergs is prodigious. Captain Ross saw several of them toge- ther in Baffin's Bay aground in water fifteen hundred feet deep ! Many of them are driven down into Hudson's Bay, and, accumulating there, diffuse excessive cold over the neigh- bouring continent, so that Captain Franklin reports, that at * Scoresby's Arctic Regions, vol. i. p. 210. t Ibid. p. 203. Dr. Latta's Observations on the Glaciers of Spitzbergen, &c, . New Phil. Jouru. vol. iii, p. 97, 126 DIFFERENCE OF CLIMATE IN NORTHERN [Ch. VII. the mouth of Hayes river, which lies in the same latitude as the north of Prussia or the south of Scotland, ice is found everywhere in digging wells, in summer, at the depth of four feet ! Difference of climate of the Northern and Southern hemi- spheres. When we compare the climate of the northern and southern hemispheres, we obtain still more instruction in regard to the influence of the distribution of land and sea on climate. The dry land in the southern hemisphere is to that of the northern in the ratio only of one to three, excluding from our consideration that part which lies between the pole and the 74 of south latitude, which has hitherto proved inaccessible. The predominance of ice in the antarctic over the arctic zone is very great ; for that which encircles the southern pole, extends to lower latitudes by ten degrees than that around the north pole *. It is probable that this remarkable difference is partly attributable, as Cook conjectured, to the existence of a con- siderable tract of high land between the 70th parallel of south latitude and the pole. There is, however, another reason suggested by Humboldt, to which great weight is due, the small quantity of land in the tropical and temperate zones south of the line. If Africa and New Holland extended farther to the south, a diminution of ice would take place in conse- quence of radiation of the heat from these continents during summer, which would warm the contiguous sea and rarefy the air. The heated aerial currents would then ascend and flow more rapidly towards the south pole, and moderate the winter. In confirmation of these views, it is stated that the cap of ice, * Captain Weddell,in 1823, reached 3 farther than Captain Cook, and arrived at 74 15' longitude, 34 17' west. After having passed through a sea strewed with numerous ice-islands, he arrived, in that high latitude, at an open ocean ; "but even if he had sailed 6 farther south, he would not have penetrated to higher latitudes than Captain Parry in the arctic circle, who reached lat. 81 10' north. The important discovery, therefore, of Captain Weddell, does not destroy the pre- sumption, that the general prevalence of ice, in low latitudes in the southern hemisphere, arises from the existence of greater tracts of land in the antarctic, than in the arctic ocean, Ch.VIL] AND SOUTHERN HEMISPHERES. 127 which extends as far as the 68 and 71 of south latitude, ad- vances more towards the equator whenever it meets a free sea ; that is, wherever the extremities of the present continents are not opposite to it ; and this circumstance seems explicable only on the principle above alluded to, of the radiation of heat from the lands so situated. Before the amount of difference between the temperature of the two hemispheres was ascertained, it was referred by astro- nomers to the acceleration of the earth's motion in its peri- helium ; in consequence of which the spring and summer of the southern hemisphere are shorter, by nearly eight days, than those seasons north of the equator. A sensible effect is pro- bably produced by this source of disturbance, but it is quite inadequate to explain the whole phenomenon. It is, however, of importance to the geologist to bear in mind, that in conse- quence of the precession of the equinoxes the two hemispheres receive alternately, each for a period of upwards of 10,000 years, a greater share of solar light and heat. This cause may sometimes tend to counterbalance inequalities resulting from other circumstances of a far more influential nature; but, on the other hand, it must sometimes tend to increase the extreme of deviation which certain combinations of causes produce at distant epochs. But, whatever may now be the inferiority of heat in the tem- perate and arctic zones south of the line, it is quite evident that the cold would be far more intense if there happened, in- stead of open sea, to be tracts of elevated land between the 55th and 70th parallel ; for, in Sandwich land, in 54 and 58 of south latitude, the perpetual snow and ice reach to the sea beach ; and what is still more astonishing, in the island of Georgia, which is in the 53 south latitude, or the same parallel as the central counties of England, the perpetual snow de- scends to the level of the ocean. When we consider this fact, and then recollect that the highest mountains in Scotland do not attain the limit of perpetual snow on this side of the equator, we learn that latitude is one only of many powerful causes, 128 CAUSES OF* [Ch. VII. which determine the climate of particular regions of the globe. The permanence of snow in the southern hemisphere, in this instance, is partly due to the floating ice, which chills the at- mosphere and condenses the vapour, so that in summer the sun cannot pierce through the foggy air. The distance to which icebergs float from the polar regions on the opposite sides of the line is, as might have been anti- cipated, very different. Their extreme limit in the northern hemisphere appears to be the Azores (north latitude 42), to which isles they are sometimes drifted from Baffin's Bay. But in the other hemisphere they have been seen, within the last two years, at different points off the Cape of Good Hope, between latitude 36 and 39.* One of these was two miles n circumference, and 150 feet high-j-. Others rose from 250 to 300 feet above the level of the sea, and were therefore of great volume below, since it is ascertained, by experiments on the buoyancy of ice floating in sea-water, that for every solid foot seen above, there must at least be eight feet below waterf. If ice-islands from the north polar regions floated as far, they might reach Cape St. Vincent, and then, being drawn by the current that always sets in from the Atlantic through the Straits of Gibraltar, be drifted into the Mediterranean, so that the serene sky of that delightful region would immediately be deformed by clouds and mists. The great extent of sea gives a particular character to cli- mates south of the equator, the winters being mild and the summers cold. Thus, in Van Diemen's land, corresponding nearly in latitude to Rome, the winters are more mild than at Naples, and the summers not warmer than those at Paris, which is 7 farther from the equator . The effect on vegetation is very remarkable : tree ferns, for instance, which require * On Icebergs in low Latitudes in the Southern Hemisphere, by Captain Hors- burgh, Hydrographer to the East India Company; read to the Royal Society, February, 1830. f Edin. New Phil. Journ., No. xv. p. 193 ; January, 1830. I Scoresby's Arctic Regions, vol. i. p. 234, Humboldt on Isothermal Lines, Ch. VII.] CHANGES OF TEMPERATURE. 129 abundance of moisture, and an equalization of the seasons, are found in Van Diemen's land in latitude 42, and in New- Zealand in south latitude 45. The orchideous parasites also advance towards the 38 and 42 of south latitude. These forms of vegetation might perhaps be developed in still higher latitudes, if the ice in the antarctic circle did not extend farther from the pole than in the arctic. Humboldt observes that it is in the mountainous, temperate, humid, and shady parts of the equatorial regions, that the family of ferns produces the greatest number of species. As we know, therefore, that ele- vation often compensates the effect of latitude in plants, we may easily understand that a class of vegetables, which grow at a certain height in the torrid zone, would flourish on the plains far from the equator, provided the temperature, mois- ture, and other necessary conditions, were equally uniform throughout the year. Changes in the position of land and sea may give rise to vicissitudes in climate. Having offered these brief remarks on the diffusion of heat over the globe in the present state of the surface, we shall now proceed to speculate on the vicissitudes of climate, which must attend those endless variations in the geographical features of our planet which are contemplated in geology. In order to confine ourselves within the strict limits of analogy, we shall assume, 1st, That the proportion of dry land to sea continues always the same. 2dly, That the volume of the land rising above the level of the sea is a constant quan- tity ; and not only that its mean, but that its extreme height, are only liable to trifling variations. 3dly, That both the mean and extreme depth of the sea are equal at every epoch ; and, 4thly, It will be consistent with due caution to assume that the grouping together of the land in great continents is a necessary part of the economy of nature ; for it is possible that the laws which govern the subterranean forces, and which act simultaneously along certain lines, cannot but produce, at every epoch, continuous mountain-chains ; so that the sub- VOL, I. K 130 CAUSES OF [Ch.VII. division of the whole land into innumerable islands may be precluded. If it be objected, that the maximum of elevation of land and depth of sea are probably not constant, nor the gathering together of all the land in certain parts, nor even perhaps the relative extent of land and water, we reply, that the argu- ments which we shall adduce will be greatly strengthened, if, in these peculiarities of the surface, there be considerable devi- ations from the present type. If, for example, all other cir- cumstances being the same, the land is at one time more divided into islands than at another, a greater uniformity of climate might be produced, the mean temperature remaining unaltered ; or if, at another era, there were mountains higher than the Himalaya, these, when placed in high latitudes, would cause a greater excess of cold. So, if we suppose that at cer- tain periods no chain of hills in the world rose beyond the height of 10,000 feet, a greater heat might then have prevailed than is compatible with the existence of mountains thrice that elevation. However constant we believe the relative proportion of sea and land to continue, we know that there is annually some small variation in their respective geographical positions, and that in every century the land is in some parts raised, and in others depressed by earthquakes, and so likewise is the bed of the sea. By these and other ceaseless changes, the configura- tion of the earth's surface has been remodelled again and again since it was the habitation of organic beings, and the bed of the ocean has been lifted up to the height of some of the loftiest mountains. The imagination is apt to take alarm when called upon to admit the formation of such irregularities of the crust of the earth, after it had become the habitation of living crea- tures ; but if time be allowed, the operation need not subvert the ordinary repose of nature, and the result is insignificant if we consider how slightly the highest mountain-chains cause our globe to differ from a perfect sphere. Chimborazo, al- Ch. VII.] CHANGES OF TEMPERATURE. 131 though it rises to more than 21,000 feet above the surface of the sea, would only be represented, on an artificial globe of about six feet in diameter, by a grain of sand less than one- twentieth of an inch in thickness*. The superficial inequalities of the earth, then, may be deemed minute in quantity, and their distribution at any particular epoch must be regarded in geology as temporary peculiarities, like the height and outline of the cone of Vesuvius in the interval between two eruptions. But, although the uneven- ness of the surface is so unimportant in reference to the mag- nitude of the globe, it is on the position and direction of these small inequalities that the state of the atmosphere and both the local and general climate are mainly dependent. Before we consider the effect which a material change in the distribution of land and sea must occasion, it may be well to remark, how greatly organic life may be affected by those minor mutations, which need not in the least degree alter the general temperature. Thus, for example, if we suppose, by a series of convulsions, a certain part of Greenland to become sea, and, in compensation, a tract of land to rise and connect Spitzbergen with Lapland, an accession not greater in amount than one which the geologist can prove to have occurred in certain districts bordering the Mediterranean, within a com- paratively modern period, this altered form of the land might occasion an interchange between the climate of certain parts of North America and of Europe, which lie in corresponding latitudes. Many European species would probably perish in consequence, because the mean temperature would be greatly lowered ; and others would fail in America, because it would there be raised. On the other hand, in places where the mean annual heat remained unaltered, some species which flourish in Europe, where the seasons are more uniform, would be unable to resist the great heat of the North American summer, or the intense cold of the winter ; while others, now fitted by their habits for the great contrast of the American seasons, would * Malte-Brun's System of Geography, book i. p. 6. K 2 132 CAUSES OP [Ch. VII. not be fitted for the insular climate of Europe*. Many plants, for instance, will endure a severe frost, but cannot ripen their seeds without a certain intensity of summer-heat and a certain quantity of light ; others cannot endure the same intensity of heat or cold. It is now established that many species of animals, which are at present the contemporaries of man, have survived great changes in the physical geography of the globe. If such species be termed modern, in comparison to races which pre- ceded them, their remains, nevertheless, enter into submarine deposits many hundred miles in length, and which have since been raised from the deep to no inconsiderable altitude. When, therefore, it is shewn that changes of the temperature of the atmosphere may be the consequence of such physical revolu- tions of the surface, we ought no longer to wonder that we find the distribution of existing species to be local, in regard to longitude as well as latitude. If all species were now, by an exertion of creative power, to be diffused uniformly throughout those zones where there is an equal degree of heat, and in all respects a similar climate, they would begin from this moment to depart more and more from their original distribution. Aquatic and terrestrial species would be displaced, as Hooke long ago observed, so often as land and water exchanged places; and there would also, by the formation of new moun- tains and other changes, be transpositions of climate, contri- buting, in the manner before alluded to, to the local extermi- nation of species. If we now proceed to consider the circumstances required for a general change of temperature, it will appear, from the facts and principles already laid down, that whenever a greater extent of high land is collected in the polar regions, the cold will augment ; and the same result will be produced when there shall be more sea between or near the tropics ; while, on the contrary, so often as the above conditions are reversed, the * According to Humboldt, the vine can be cultivated with advantage 10 far' ther north in Europe than in North America. Ch. VII.] CHANGES OF TEMPERATURE. 133 heat will be greater. If this be admitted, it will follow as a corollary, that unless the superficial inequalities of the earth be fixed and permanent, there must be never-ending fluctua- tions in the mean temperature of every zone, and that the climate of one era can no more be a type of every other, than is one of our four seasons of all the rest. It has been well said, that the earth is covered by an ocean, and in the midst of this ocean there are two great islands, and many smaller ones ; for the whole of the continents and islands occupy an area scarcely exceeding one-fourth of the whole superficies of the spheroid. Now, on a fair calculation, we may expect that at any given epoch there will not be more than about one-fourth dry land in a particular region ; such, for example, as the arctic and antarctic circles. If, therefore, at present there should happen in the only one of these regions which we can explore, to be much more than this average pro- portion of land, and some of it above five thousand feet in height, this alone affords ground for concluding that, in the present state of things, the mean heat of the climate is below that which the earth's surface, in its more ordinary state, would enjoy. This presumption is heightened, when we remember that the mean depth of the Atlantic ocean is calculated to be about three miles, and that of the Pacific four miles * ; so that we might look not only for more than two-thirds sea in the frigid zones, but for water of great depth, which could not readily be reduced to the freezing point. The same opinion is further confirmed, when we compare the quantity of land lying between the poles and the 30th parallels of north and south latitude, and the quantity placed between those parallels and the equator ; for it is clear, that at present we must have not only more than the usual degree of cold in the polar * See Young's Nat. Phil. Lect. 47. Laplace seems often to have changed his opinion, reasoning from the depth required to account for the phenomena of the tides; hut his final conclusion respecting the sea was f que sa profondeur moyenne est du meme ordre que la hauteur moyenne des continens et des iles au-dessus de son niveau, hauteur qui ne surpasse pas mille metres (3280 ft.).' Mec. Celeste, Bk. 11. et Syst. du Monde, p. 254, 134 CAUSES OF [Ch, VII. regions, but also less than the average quantity of heat gene- rated in the intertropical zone. Position of land and sea which might produce the extreme of cold of which the earth's surface is susceptible. In order to simplify our view of the various changes in climate, which different combinations of geographical circumstances may pro- duce, we shall first consider the conditions necessary for bring- ing about the extreme of cold, or what may be termed the winter of the ' great year,' or geological cycle, and afterwards, the conditions requisite for producing the maximum of heat, or the summer of the same year. To begin with the northern hemisphere. Let us suppose those hills of the Italian peninsula and of Sicily, which are of comparatively modern origin, and contain many fossil shells identical with living species, to subside again into the sea, from which they have been raised, and that an extent of land of equal area and height (varying from one to three thousand feet) should rise up in the Arctic ocean between Siberia and the north pole. In speaking of such changes, we need not allude to the manner in which we conceive it possible that they may be brought about, nor of the time required for their accomplishment, reserving for a future occasion, not only the proofs that revolutions of equal magnitude have taken place, but that analogous mutations are still in gradual progress. The alteration now supposed in the physical geography of the northern regions would cause additional snow and ice to accumulate where now there is usually an open sea ; and the temperature of the greater part of Europe would be somewhat lowered, so as to resemble more nearly that of corresponding latitudes of North America ; or, in other words, it might be necessary to travel about 10 farther south, in order to meet with the same climate which we now enjoy. There would be no compensation derived from the disappearance of land in the Mediterranean countries ; for, on the contrary, the mean heat of the soil so situated, is probably far above that which would belong to the sea, by which we imagine it to be replaced. Ch. VII.] CHANGES OF TEMPERATURE. 135 But let the configuration of the surface be still further varied, and let some large district within or near the tropics, such as Mexico, for example, with its mountains rising to the height of twelve thousand feet and upwards, be converted into sea, while lands of equal elevation and extent are transferred to the arctic circle. From this change there would, in the first place, result a sensible diminution of temperature near the tropic, for the soil of Mexico would no longer be heated by the sun ; so that the atmosphere would be less warm, as also the Atlantic, and the Gulf stream. On the other hand, the whole of Europe, Northern Asia, and North America, would feel the influence of the enormous quantity of ice and snow, now generated at vast heights on the new arctic continent. If, as we have already seen, there are some points in the southern hemisphere where snow is perpetual to the level of the sea, in latitudes as low as central England, such might now assuredly be the case throughout a great part of Europe. If at present the extreme limits of drifted icebergs are the Azores, they might easily reach the equator after the changes above sup- posed. To pursue the subject still farther, let the Himalaya mountains, with the whole of Hindostan, sink down, and their place be occupied by the Indian ocean, and then let an equal extent of territory and mountains, of the same vast height, stretch from North Greenland to the Orkney islands. It seems difficult to exaggerate the amount to which the climate of the northern hemisphere would now be cooled down. But, notwithstanding the great refrigeration which would thus be produced, it is probable that the difference of mean temperature between the arctic and equatorial latitudes would not be increased in a very high ratio, for no great disturbance can be brought about in the climate of a particular region, without immediately affecting all other latitudes, however re- mote. The heat and cold which surround the globe are in a state of constant and universal flux and reflux. The heated and rarefied air is always rising and flowing from the equator towards the poles in the higher regions of the atmosphere, and, 136 CAUSES OF [Ch. VII in the lower, the colder air is flowing back to restore the equi librium. That this circulation is constantly going on in the aerial currents is not disputed ; the fact, indeed, was illustrated in a striking manner by an event which happened in the pre- sent century. The trade wind continually blows with great force from the island of Barbadoes to that of St. Vincent's ; notwithstanding which, during the eruption of the volcano in the Island of St. Vincent, in 1812, ashes fell in profusion from a great height in the atmosphere upon Barbadoes. This ap- parent transportation of matter against the wind, confirmed the opinion of the existence of a counter-current in the higher regions, which had previously rested on theoretical con- clusions *. That a corresponding interchange takes place in the seas, is demonstrated, according to Humboldt, by the cold which is found to exist at great depths between the tropics \ and, among other proofs, may be mentioned the great volume of water which the Gulf stream is constantly bearing northwards, while another current flows from the north along the coast of Green- land and Labrador, and helps to restore the equilibrium f. Currents of heavier and colder water pass from the poles towards the equator, which cool the inferior parts of the ocean ; so that the heat of the torrid zone, and the cold of the polar circle balance each other. The refrigeration, therefore,, of the polar regions, resulting from the supposed alteration in the distribution of land and sea, would be immediately commu- nicated to the tropics, and from them would extend to the antarctic circle, where the atmosphere and the ocean would be cooled, so that ice and snow would augment. Although the mean temperature of higher latitudes in the southern hemi- * DanielPs Meteorological Essays, &c., p. 103. f In speaking of the circulation of air and water in this chapter, no allusion is made to the trade winds, or to irregularities in the direction of currents, caused by the rotatory motion of the earth. These causes prevent the movements from being direct from north to south, or from south to north, but they do not affect the theory of a constant circulation. Ch. VII.] CHANGES OF TEMPERATURE. 137 sphere is, as we have stated, for the most part lower than that of the same parallels in the northern, yet for a considerable space on each side of the line, the mean annual heat of the waters is found to be the same in corresponding parallels. When, therefore, by the new position of the land, the gene- rating of icebergs had become of frequent occurrence in the northern temperate zone, and when they were frequently drifted as far as the equator, the same degree of cold would immediately be communicated as far as the tropic of Capricorn, and from thence to the lands or ocean to the south. The freedom, then, of the circulation of heat and cold from pole to pole being duly considered, it will be evident that the mean quantity of solar heat which at two different periods visits the same point, may differ far more widely than the mean quantity which any two points receive in the same parallels of latitude, at one and the same period. For the range of tem- perature in a given zone, or in other words, the curves of the isothermal lines, must always be circumscribed within narrow limits, the climate of each place in that zone being controlled by the combined influence of the geographical peculiarities of all other parts of the earth. Whereas, if we compare the state of things as existing at two distinct epochs, a particular zone may at one time be under the influence of one class of dis- turbing causes, as for example those of a refrigerating nature, and at another time may be affected by a combination of oppo- site circumstances. The lands to the north of Greenland cause the present climate of North America to be colder than that of Europe in the same latitudes, but they also affect, to a cer- tain extent, the temperature of the atmosphere in Europe; and the entire removal from the northern hemisphere of that great source of refrigeration would not assimilate the mean temperature of America to that now experienced in Europe, but would render the continents on both sides of the Atlantic much warmer. To return to the state of the earth after the changes before supposed by us, we must not omit to dwell on the important 138 CAUSES OF [Ch.VII. effects to which a wide expanse of perpetual snow would give rise. It is probable that nearly the whole sea, from the poles to the parallels of 45, would be frozen over, for it is well known that the immediate proximity of land is not essential to the formation and increase of field ice, provided there be in some part of the same zone a sufficient quantity of glaciers generated on or near the land, to cool down the sea. Captain Scoresby, in his account, of the arctic regions, observes, that when the sun's rays ( fall upon the snow-clad surface of the ice or land, they are in a great measure reflected, without pro- ducing any material elevation of temperature ; but when they impinge on the black exterior of a ship, the pitch on one side occasionally becomes fluid, while ice is rapidly generated at the other*.' Now field ice is almost always covered with snow f, and thus not only land as extensive as our existing conti- nents, but immense tracts of sea in the frigid and tempe- rate zones, might present a solid surface covered with snow, and reflecting the sun's rays for the greater part of the year. Within the tropics, moreover, where we suppose the ocean to predominate, the sky would no longer be serene and clear, as in the present era ; but the melting of floating ice would cause quick condensations of vapour, and fogs and clouds would deprive the vertical rays of the sun of half their power. The whole planet, therefore, would receive annually a smaller pro- portion of solar influence, and the external crust would part, by radiation, with some of the heat which had been accumu- lated in it, during a different state of the surface. This heat would be dissipated into the spaces surrounding our atmo- sphere, which, according to the calculations of M. Fourier, have a temperature much inferior to that of freezing water. At this period, the climate of equinoctial lands might re- semble that of the present temperate zone, or perhaps be far more wintery. They who should then inhabit such small isles and coral reefs, as are now seen in the Indian ocean and South * See Scoresby's Arctic Regions, vol. i. p. 378. f Ib. p. 320. Ch. VII. CHANGES OF TEMPERATURE. 139 Pacific, would wonder that zoophytes of such large dimensions had once been so prolific in those seas ; or if, perchance, they found the wood and fruit of the cocoa-nut tree or the paltn silicified by the waters of some ancient mineral spring, or in- crusted with calcareous matter, they would muse on the revo- lutions that had annihilated such genera, and replaced them by the oak, the chestnut, and the pine. With equal admira- tion would they compare the skeletons of their small lizards with the bones of fossil alligators and crocodiles more than twenty feet in length, which, at a former epoch, had multiplied between the tropics ; and when they saw a pine included in an iceberg, drifted from latitudes which we now call temperate, they would be astonished at the proof thus afforded, that forests had once grown where nothing could be seen in their own times but a wilderness of snow. As we have not yet supposed any mutations to have taken place in the relative position of land and sea in the southern hemisphere, we might still increase greatly the intensity of cold, by transferring the land still remaining in the equatorial and contiguous regions, to higher southern latitudes; but it is unnecessary to pursue the subject farther, as we are too igno- rant of the laws governing the direction of subterranean forces, to determine whether such a crisis be within the limits of pos- sibility. At the same time we may observe, that the distri- bution of land at present is so remarkably irregular, and appears so capricious, if we may so express ourselves, that the two extremes of terrestrial heat and cold are probably sepa- rated very widely from each other. The globe may now be equally divided, so that one hemisphere shall be entirely covered with water, with the exception of some promontories and islands, while the other shall contain less water than land ; and what is still more extraordinary, on comparing the extra- tropical lands in the northern and southern hemispheres, the former are found to be to the latter in the proportion of thirteen to one * ! To imagine all the lands, therefore, in high; * Huinboldt, on Isothermal Lines. 140 CAUSES OF [Ch. VII. and all the sea in low latitudes, would scarcely be a more anomalous state of the surface. Position of land and sea which might give rise to the extreme of heat. Let us now turn from the contemplation of the win- ter of the ' great year/ and consider the opposite train of cir- cumstances, which would bring on the spring and summer. That some part of the vast ocean which forms the Atlantic and Pacific, should at certain periods occupy entirely one or both of the polar regions, and should extend, interspersed with islands only, to the parallels of 40, and even 30, is an event that may be supposed in the highest degree probable, in the course of many great geological revolutions. In order to esti- mate the degree to which the general temperature would then be elevated, we should begin by considering separately the effect of the diminution of certain portions of land, in high northern latitudes, which might cause the sea to be as open in every direction, as it is at present towards the north pole, in the meri- dian of Spitzbergen. By transferring the same lands to the torrid zone, we might gain farther accessions of heat, and cause the ice towards the south pole to diminish. We might first continue these geographical mutations, until we had produced as mild a climate in high latitudes as exists at those points in the same parallel where the mean annual heat is now greatest. We should then endeavour to calculate what further alterations would be required to double the amount of change ; and the great deviation of isothermal lines at present seems to authorize us to infer, that without an entire revolution of the surface, we might cause the mean temperature to vary to an extent equivalent to 20 or even 30 of latitude, in other words, we might transfer the temperature of the torrid zone, to the mean parallel, and of the latter, to the arctic regions. By additional transpositions, therefore, of land and sea, we might bring about a still greater variation, so that, throughout the year, all signs of frost should disappear from the earth. The plane of congelation would rise in the atmosphere in all latitudes ; and as our hypothesis would place all the highest Ch. VII.] CHANGES OF TEMPERATURE. 141 mountains in the torrid zone, they would be clothed with rich vegetation to their summits. We must recollect that even now it is necessary to ascend to the height of 15,000 feet in the Andes under the line, and in the Himalaya mountains, which are without the tropic, to 17,000 feet, before we reach the limit of perpetual snow. When the absorption of the solar rays was unimpeded, even in winter, by a coat of snow, the mean heat of the earth's crust would augment to considerable depths, and springs, which we know to be an index of the mean tem- perature of the climate, would be warmer in all latitudes. The waters of lakes, therefore, and rivers, would be much hotter in winter, and would be never chilled in summer by the melting of snow. A remarkable uniformity of climate would pre- vail amid the numerous archipelagos of the polar ocean, amongst which the tepid waters of equatorial currents would freely circulate. The general humidity of the atmosphere would far exceed that of the present period, for increased heat would promote evaporation in all parts of the globe. The winds would be first heated in their passage over the tropical plains, and would then gather moisture from the surface of the deep, till, charged with vapour, they would arrive at northern regions, and, encountering a cooler atmosphere, would dis- charge their burden in warm rain. If, during the long night of a polar winter, the snows should whiten the summit of some arctic islands, and ice collect in the bays of the remotest Thule, they would be dissolved as rapidly by the returning sun, as are the snows of Etna by the blasts of the sirocco. We learn from those who have studied the geographical dis- tribution of plants, that in very low latitudes, at present, the vegetation of small islands remote from continents has a pecu- liar character, and the ferns and allied families, in particular, bear a great proportion to the total number of other vegetables. Other circumstances being the same, the more remote the isles are -from the continents, the greater does this proportion be- come. Thus, in the continent of India, and the tropical parts of New Holland, the proportion of ferns to the phanerogamic 142 CAUSES OF [Ch. VII. plants is only as one to twenty-six ; whereas, in the South- Sea Islands, it is as one to four, or even as one to three *. AYe might expect, therefore, in the summer of the < great year,' which we are now considering, that there would be a great predominance of tree-ferns and plants allied to palms and arborescent grasses in the isles of the wide ocean, while the dicotyledonous plants and other forms now most common in temperate regions would almost disappear from the earth. Then might those genera of animals return, of which the me- morials are preserved in the ancient rocks of our continents. The huge iguanodon might reappear in the woods, and the ichthyosaur in the sea, while the pterodactyle might flit again through umbrageous groves of tree-ferns. Coral reefs might be prolonged beyond the arctic circle, where the whale and the narwal now abound. Turtles might deposit their eggs in the sand of the sea-beach, where now the walrus sleeps, and where the seal is drifted on the ice-floe. But, not to indulge these speculations farther, we may ob- serve, in conclusion, that however great, in the lapse of ages, may be the vicissitudes of temperature in every zone, it accords with our theory that the general climate should not experience any sensible change in the course of a few thousand years, be- cause that period is insufficient to affect the leading features of the physical geography of the globe. Notwithstanding the apparent uncertainty of the seasons, it is found that the mean temperature of particular localities is very constant, provided we compare observations made at different periods for a series of years. Yet, there must be exceptions to this rule, and even the labours of man have, by the drainage of lakes and marshes, and the felling of extensive forests, caused such changes in the atmosphere as raise our conception of the more important in- fluence of those forces to which even the existence, in certain latitudes, of land or water, hill or valley, lake or sea, must be * Ad. Brougniart, Consid. Generates sur la Nat. de la Vegt., &c. Ann. des Sciences Nat., Nov. 1828. Ch. VII.] CHANGES OF TEMPERATURE. 143 ascribed. If we possessed accurate information of the amount of local fluctuation in climate in the course of twenty cen- turies, it would often, undoubtedly, be considerable. Certain tracts, for example, on the coast of Holland and of England, consisted of cultivated land in the time of the Romans, which the sea, by gradual encroachments, has at length occupied. Here an alteration has been effected ; for neither the division of heat in the different seasons, nor the mean annual heat of the atmosphere investing the sea is precisely the same as that which rests on the land. In those countries also where the earthquake and volcano are in full activity, a much shorter period may produce a sen- sible variation. The climate of the once fertile plain of M al- pais in Mexico must differ materially from that which prevailed before the middle of the last century ; for, since that time, six mountains, the highest of them rising 1600 feet above the plateau, have been thrown up by volcanic eruptions. It is by the repetition of an indefinite number of local revolutions due to volcanic and various other causes, that a general change of climate is finally brought about. CHAPTER VIII. Further examination of the question as to the discordance of the ancient and modern causes of change That the geographical features of the northern hemisphere, at the period of the deposition of the carboniferous strata, were such as might, according to the theory hefore explained, have given rise to an extremely hot climate State of the surface when the transition and mountain limestones, coal-sandstones, and coal originated Change in the physical geo- graphy of northern latitudes, between the era of the formation of the carbo- niferous series and the lias Character of organic remains, from the lias to the chalk inclusive State of the surface when these deposits originated Great accession of land, and elevation of mountain-chains, between the consolidation of the newer secondary and older tertiary rocks Consequent refrigeration of climate Abrupt transition from the organic remains of the secondary to those of the tertiary strata Maestricht beds Remarks on the theory of the diminu- tion of central heat. That the geographical features of the northern hemisphere at the period of the deposition of the carboniferous strata were such as might have given rise to an extremely hot climate. We stated, in the sixth chapter, our reasons for concluding that the mean annual temperature of the northern hemisphere was considerably more elevated when the old carboniferous strata were deposited ; as also that the climate had been modi- fied more than once since that epoch, and that it approximated by successive changes more and more nearly to that now pre- vailing in the same latitudes. Further, we endeavoured, in the last chapter, to prove that vicissitudes in climate of no less importance may be expected to recur in future, if it be ad- mitted that causes now active in nature have power, in the lapse of ages, to vary to an unlimited extent the relative posi- tion of land and sea. It next remains for us to inquire whether the alterations, which the geologist can prove to have actually taken place at former periods, in the geographical features of the northern hemisphere, coincide in their nature, and in the time of their occurrence, with such revolutions in climate as Ch. VIII.] CHANGES IN PHYSICAL GEOGRAPHY. 145 would naturally have followed, according to the meteorological principles already explained. We may select the great carboniferous series, including the transition and mountain limestones, and the coal, as the oldest system of rocks of which the organic remains furnish any deci- sive evidence as to climate. We have already insisted on the indications which they afford of great heat and uniformity of temperature, extending over a vast area, from about 45 to 60, or, perhaps, if we include Melville Island, to near 75 north latitude*. When we attempt to restore in imagination the distribution of land and sea, as they existed at that remote epoch, we dis- cover that our information is at present limited to latitudes north of the tropic of cancer, and we can only hope, therefore, to point out that the';condition of the earth, so far as relates to our temperate and arctic zones, was such as the theory before offered would have led us to anticipate. Now there is scarcely any land hitherto examined in Europe, Northern Asia, or North America, which has not been raised from the bosom of the deep, since the origin of the carboniferous rocks, or which, if previously raised, has not subsequently acquired additional altitude. If we were to submerge again all the marine strata, from the transition limestone to the most recent shelly beds, the summits of some primary mountains alone would remain above the waters. These facts, it is true, considered singly, are not conclusive as to the universality of the ancient ocean in the northern hemisphere, because the movements of earth- quakes occasion the subsidence as well as the upraising of the surface, and by the alternate rising and sinking of particular spaces, at successive periods, a great area may become entirely * Our ancient coal-formatioii has not been found in Italy, Spain, Sicily, or any of the more southern countries of Europe. "\Yhether any of the ainmonitiferous limestones of the Southern Apennines and Sicily (Taormina for example) can be considered as of contemporaneous origin with our carboniferous series, is not yet determined; but it is conjectured, from the general character of the organic re- mains of the Apennine limestones, that they belong to some part of our secondary series, from the lias to the chalk inclusive. VOL. I. L 146 PROOFS OF FORMER [Ch. VIII. i covered with marine deposits, although the whole has never been beneath the waters at one time, nay, even though the re- lative proportion of land and sea may have continued unaltered ; throughout the whole period. There is, however, the highest presumption against such an hypothesis, because the land in the northern hemisphere is now in great excess, and this circumstance alone should induce us to suppose that, amid the repeated changes which the surface has undergone, the sea has usually predominated in a much greater degree. But when we study the mineral composition and fossil contents of the older strata, we find evidence of a more positive and unequivocal kind in confirmation of the same opinion. State of the surface when the transition and mountain lime- stones, coal-sandstones, and coal originated. Calcareous rocks, containing the same class of organic remains as our transition and mountain limestones,, extend over a great part of the central and northern parts of Europe, are found in the lake district of North America, and even appear to occur in great abundance as far as the border of the Arctic Sea *. The organic remains of these rocks consist principally of marine shells, corals, and the teeth and bones of fish ; and their nature, as well as the continuity of the calcareous beds of homogeneous mineral com- position, concur to prove that the whole series was formed in a deep and expansive ocean, in the midst of which, however, there were many isles. These isles were composed partly of primary and partly of volcanic rocks, which being exposed to * It appears from the observations of Dr. Richardson, made during the expedi- tion under the command of Captain Franklin to the north-west coast of America, and from the specimens presented by him to the Geological Society of London, that, between the parallels of 60 and 70 north latitude, there is a great calcareous formation, stretching towards the mouth of the Mackenzie river, in which are included corallines, products, terebratulites, &c., having a close affinity in generic character to those of our mountain limestone, of which the group has been con- sidered the equivalent. There is also in the same region a newer series of strata, in which are shales with impressions of ferns, lepidodendrons, and other vege- tables, and also ammonites. These, it is supposed, may belong to the age of our oolitic series. Proceedings of Geological Society, March, 1828. Ch. VIII.] CHANGES IN PHYSICAL GEOGRAPHY. 147 the erosive action of torrents, to the undermining power of the waves beating against the cliffs, and to atmospheric decompo- sition, supplied materials for pebbles, sand, and shale, which, together with substances introduced by mineral springs and volcanos in frequent eruption, contributed the inorganic parts of the carboniferous strata. The disposition of the beds in that portion of this group which is of mechanical origin, and which incloses the coal, has been truly described to be such as would result from the waste of small islands placed in rows and forming the highest points of ridges of submarine mountains. The disintegration of such clusters of isles would produce around and between them detached deposits of various dimensions, which, when subse- quently raised above the waters, would resemble the strata formed in a chain of lakes. The insular masses of primary rock would preserve their original relative superiority of height, and would often surround the newer strata on several sides, like the boundary heights of lake basins *. As might have been expected, the zoophytic, and shelly limestones of the same era, (as the mountain limestone,) some- times alternate with the rocks of mechanical origin, but appear to have been, in ordinary cases, diffused far and wide over the bottom of the sea, remote from any islands, and where no grains of sand were transported by currents. The associated volcanic rocks resemble the products of submarine eruptions, the tuffs being sometimes interstratified with calcareous shelly beds, or with sandstones, just as might be expected if the sand and ejected matter of which they are probably composed had been intermixed with the waters of the sea, and had then sub- sided like other sediment. The lavas also often extend in spreading sheets, and must have been poured out on a surface rendered horizontal by sedimentary depositions. There is, moreover, a compactness and general absence of porosity in these igneous rocks which distinguishes them from most of * See some ingenious remarks to this effect, in the work of M. Ad. Brongniart, Consid. Generates sur la Nat. de la Veget. &c. Ann. des Sci. Nat., Nov. 1828. L 2 148 PROOFS OF FORMER [Ch. VIII. those which are produced on the sides of Etna or Vesuvius, and other land volcanos. The modern submarine lavas of Sicily, which alternate with beds of shells specifically identical with those now living in the Mediterranean, have almost all their cavities filled with cal- careous and other ingredients, and have been converted into amygdaloids, and this same change we must suppose such parts of the Etnean lava currents as enter the sea to be undergoing at present, because we know the water on the adjoining coast to be copiously charged with carbonate of lime in solution. It is, therefore, one among many reasons for inferring the sub- marine origin of our ancient trap rocks, that there are scarcely any instances, in which the cellular hollows, left by bubbles of elastic fluid, have not subsequently been filled by calcareous, siliceous, or other mineral ingredients, such as now abound in the hot springs of volcanic countries. If, on the other hand, we examine the fossil remains in these strata, we find the vegetation of the coal strata declared by botanists to possess the characters of an insular, not a conti- nental flora, and we may suppose the carbonaceous matter to have been derived partly from trees swept from the rocks by torrents into the sea, and partly from such peaty matter as often discolours and blackens the rills flowing through marshy grounds in our temperate climate, where the vegetation is pro- bably less rank, and its decomposition less rapid than in the moist and hot climate of the era under consideration. There is, however, as yet no well authenticated instance of the re- mains of a saurian animal having been found in a member of the carboniferous series*. * It is, indeed, stated, that among other fossils collected from the mountain limestone of Northumberland, the Rev. Charles V. Vernon Harcourt has been fortunate enough Unius sese dominum fecisse lacertae, having found a saurian vertebra together with patellae and echinal spines, and an impression of a fern analogous to those of the coal-measures in the mountain lime- stone. Annual Report of the Yorkshire Phil. Soc. for 1826, p. 14. But I am informed by Mr. Harcourt himself, that the vertebra was discovered in loose alluvium. Ch. VIII.] CHANGES IN PHYSICAL GEOGRAPHY. 149 The larger oviparous reptiles usually inhabit rivers of con- siderable size in warm latitudes, and had crocodiles and other animals of that class been abundant in a fossil state, as in some of the newer secondary formations, we must have inferred the existence of many rivers, which could only have drained large tracts of land. Nor have the bones of any terrestrial mam- malia rewarded our investigations. Had any of these, be- longing to quadrupeds of large size, occurred, they would have supplied an argument against the resemblance of the ancient northern archipelagos to those of the modern Pacific, since in the latter no great indigenous quadrupeds have been met with. It is, indeed, a general character of small islands situated at a remote distance from -continents, to be altogether destitute of land quadrupeds, except such as appear to have been conveyed to them by man. Kerguelen's land, which is of no inconsider- able size, placed in a latitude corresponding to that of the Scilly islands, may be cited as an example, as may all the groups of fertile islands in the Pacific Ocean between the tropics, where no quadrupeds have been found, except the dog, the hog, and the rat, which have probably been brought to them by the natives, and also bats, which may have made their way along the chain of islands which extend from the shores of New Guinea far into the southern Pacific *. Even the isles of New Zealand, which may be compared to Ireland and Scotland in dimensions, appear to possess no indigenous quadrupeds, except the bat ; and this is rendered the more striking, when we recollect that the northern extremity of New Zealand stretches to latitude 34, where the warmth of the climate must greatly favour the prolific development of organic life. Lastly, no instance has yet been discovered of a pure lacustrine forma- tion of the carboniferous era; although there are some instances of shells, apparently fresh-water, which may have been washed in by small streams, and do not by any means imply a consi- derable extent of dry land. All circumstances, therefore, point to one conclusion : * Pricliard's Phys. Hist, of Man., vol. i., p. 75. 150 CHANGES OF THE SURFACE [Ch. VIII. the subaqueous character of the igneous products the con- tinuity of the calcareous strata over vast spaces the marine nature of their organic remains the basin-shaped disposition of the mechanical rocks the absence of large fluviatile and of land quadrupeds the non-existence of pure lacustrine strata the insular character of the flora, all concur with wonderful harmony to establish the prevalence throughout the northern hemisphere of a great ocean, interspersed with small isles. If we seek for points of analogy to this state of things,, we must either turn to the north Pacific, and its numerous submarine or insular volcanos between Kamtschatka and New Guinea ; or, in order to obtain a more perfect counterpart to the coralline and shelly limestones, we may explore the archi- pelagos of the south Pacific, between Australia and South America, where volcanos are not wanting, and where coral reefs, consisting in great part of compact limestone, are spread over an area not inferior, perhaps, to that of our ancient cal- careous rocks, though we suppose these to be prolonged from the lakes of North America to central Europe *. No geologists have ever denied, that when our oldest con- chiferous rocks were produced, great continents were wanting in the temperate and arctic zones north of the equator ; but they have even gone farther, and have been disposed to specu- late on the universality of what they termed the primeval ocean. As well might the New Zealander, who had surveyed and measured the quantity of land between the south pole and the tropic of Capricorn, assume that the same proportion would be found to exist between the tropic of Cancer and the north pole. By this generalization, he would imagine twelve out of thirteen parts of the land of our temperate and arctic zones to be submerged. Such theorists should be reminded, that if the ocean was ever universal, its mean depth must have been infe- rior, and if so, the probability of deep water within the arctic circle is much lessened, and the likelihood of a preponderance of ice increased, and the heat of the ancient climate rendered * See vol. ii. ch. 18. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 151 more marvellous. To this objection, however, they will answer, that they do not profess to restrict themselves to existing ana- logies, and they may suppose the volume of water in the primeval ocean to have been greater. Besides, the high tem- perature, say they, was caused by heat which emanated from the interior of the new-born planet. In vain should we suggest to such reasoners, that when the ocean was in excess in high latitudes, the land in all probabi- lity predominated within the tropics, where, being exposed to the direct rays of the sun, it may have heated the winds and currents which flowed from lower to higher latitudes. In vain should we contend that a greater expanse of ocean, if general throughout the globe, would imply a comparative evenness of the superficial crust of the earth, and such an hypothesis would oblige us to conclude that the disturbances caused by subter- ranean movements in ancient times were inferior to those of later date. Will these arguments be met by the assumption that earthquakes were feebler in the earlier ages, or wholly unknown, as, according to Werner, there were no volcanos? Such a doctrine would be inconsistent with other popular pre- judices respecting the extraordinary violence of the operations of nature in the olden time ; and it is probable, therefore, that refuge will be taken in the old dogma of Lazzaro Moro, who imagined that the bed of the first ocean was as regular as its surface, and if so, it may be contended that sufficient time did not elapse between the creation of the world and the origin of the carboniferous strata, to allow the derangement necessary to produce great continents and Alpine chains. Changes in the physical geography of northern latitudes, between the era of the formation of the carboniferous series and the lias. r But it would be idle to controvert, by reference to modern analogies, the conjectures of those who think they can ascend in their retrospect to the origin of our system. Let us therefore consider what changes the crust of the globe suf- fered after the consolidation of that ancient series of rocks to which we have adverted. Now, there is evidence that, before 152 CHANGES OF THE SURFACE [Ch. VIII. our secondary strata were formed, those of older date (from the old red sandstone to the coal inclusive) were fractured and contorted, and often thrown into vertical positions. We cannot enter here into the geological details by which it is demonstrable, that, at an epoch extremely remote, some parts of the carboniferous series were lifted above the level of the sea, others sunk to greater depths beneath it, and the former, being no longer protected by a covering of water, were par- tially destroyed by torrents and the waves of the sea, and sup- plied matter for newer horizontal beds. These were arranged on the truncated edges of the submarine portions of the more ancient series, and the fragments included in the more modern conglomerates still retain their fossil shells and corals, so as to enable us to determine the parent rocks from whence they were derived*. By such remodelling of the surface, the small islands of the first period increased in size, and new land was introduced into northern regions, consisting partly of primary and volcanic rocks, and partly of the newly-raised carboni- ferous strata. Among other proofs that earthquakes were then governed by the same laws which now regulate the subterranean forces, we find that they were restrained within limited areas, so that the site of Germany was not agitated, while that of some parts of England was convulsed. The older rocks, therefore, re- mained in some cases undisturbed at the bottom of the ancient ocean, and in this case the strata of the succeeding epoch were deposited upon them in conformable position. By reference to groups largely developed on the continent, * Thus, for example, on the banks of the Avon, in the Bristol coal-field, the dolomitic conglomerate, a rock of an age intermediate between the carboniferous series and the lias, rests on the truncated edges of the coal and mountain lime- stone, and contains rolled and angular fragments of the latter, in which are seen the characteristic mountain-limestone fossils. Fcr accurate sections illustrating the disturbances which recks of the carboniferous series underwent before the newer red sandstone was formed, the reader should consult the admirable memoir on the south-western coal district of England, by Dr. Buckland and Mr. Conybeare. Geol. Trans., vol. i., second series. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 153 but which are some of them entirely wanting, and others feebly represented in our own country, we find that the appa- rent interruption in the chain of events between the formation of our coal and the lias arises merely from local deficiency in the suite of geological monuments*. During the great interval which separated the formation of these groups, new species of animals and plants made their appearance, and in their turn became extinct; volcanos broke out, and were at length ex- hausted ; rocks were destroyed in one region, and others accu- mulated elsewhere ; while, in the mean time, the geographical condition of the northern hemisphere suffered material modifi- cations. Yet the sea still extended over the greater part of the area now occupied by the lands which we inhabit, and was even of considerable depth in many localities where our highest mountain-chains now rise. The vegetation, during a part at least of this new period (from the lias to the chalk inclusive), appears to have approached to that of the larger islands of the equatorial zone f. These islands appear to have been drained by rivers of considerable size, which were inhabited by croco- diles and gigantic oviparous reptiles, both herbivorous and carnivorous, belonging for the most part to extinct genera. Of the contemporary inhabitants of the land we have as yet acquired but scanty information, but we know that there were flying reptiles, insects, and small mammifera, allied to the opossum. In further confirmation of the opinion that countries of con- siderable extent now rose above the sea in the temperate zone, * In man)' parts of Germany, the newer red sandstone, and other rocks of about the same age, lie in conformable strata on the coal. In some districts, as in the Thuringerwald, among others, there is an immense series of formations intervening between the coal and the lias ; one of these groups, called the muschetkatkstein, \\hkh seems to have no existence in England, is of great thickness and full of organic remains. See Professor Sedgwick's Memoir on the Geological Relations and Internal Structure of the Magnesian Limestone, &c. Geol. Trans., second series, vol. iii. part i. p. 121. f Ad. Brongniart, Consid. Generates sur la Nat. de la Vegei, &c. Ann. des Sci. Nat., Nov. 1828. 154 CHANGES OF THE SURFACE [Ch. VIII j we may mention the discovery of a large estuary formation in the south-east of England of higher antiquity than the chalk, containing terrestrial plants and fresh-water testacea, tortoises, and large reptiles, in a word, such an assemblage as the delta of the Ganges, or a large river in a hot climate might be ex- pected to produce *. In the present state of our knowledge, we cannot pretend to institute a close comparison between the climate which pre- vailed during the gradual deposition of our secondary forma- tions and that of the older carboniferous rocks, for the general temperature of the surface must at both epochs have been so dissimilar to that now experienced in the same, or perhaps in any latitudes, that proofs from analogy lose much of their value, and a larger body of facts is required to support theo- retical conclusions. If the signs of intense heat diminish, as some suppose, in the newer groups of this great series, there are nevertheless indications in the animal forms of the conti- nued prevalence of a climate which we might consider as tropi- cal in its character. Increase of land and elevation of mountains between the ori- gin of the newer secondary and oldest tertiary formations. We may now turn our attention to the phenomena of the tertiary strata, which afford evidence of an abrupt transition from one description of climate to another. If this remarkable break in the regular sequence of physical events is merely apparent, arising from the present imperfect state of our knowledge, it nevertheless serves to set in a clearer point of view the "intimate connexion between great changes in the physical geography of the earth, and revolutions in the mean * We do not mean to compare the extent of the Wealden formation (from the Weald clay to the Purbeck limestone inclusive) to that of the Gangetic delta, for we shall afterwards see that the most modern addition made to the latter is equal in superficial area to North and South Wales. But, judging from the great con- tinuity of some minor subdivisions of the Wealden group in our island, charac- terized as they are throughout their whole range by certain fresh-water remains, we may safely conclude that a considerable body of fresh water must have been permanently supplied by a large river. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 155 temperature of the air and water. We have already shown that, when the climate was hottest, the northern hemisphere was for the most part occupied by the ocean, and it remains for us to point out, that the refrigeration did not become con- siderable until a very large portion of that ocean was converted into land, nor even until it was in some parts replaced by high mountain-chains. Nor did the cold reach its maximum until these chains attained their full height, and the lands their full extension. A glance at the best geological maps now constructed of various countries in the northern hemisphere, whether in North America or Europe, will satisfy the inquirer that the greater part of the present land has been raised from the deep, either between the period of the deposition of the chalk and that of the strata termed tertiary, or at subsequent periods, during which various tertiary groups were formed in succession. For, as the secondary rocks, from the lias to the chalk inclusive, are, with a few unimportant exceptions, marine, it follows that every district now occupied by them has been converted into land since they originated. We may prove, by reference to the relative altitudes of the secondary and tertiary groups, and several other circumstances, that a considerable part of the elevation of the older series was accomplished before the newer was formed. The Apennines, for example, as the Italian geologists hinted long before the time of Brocchi, and as that naturalist more clearly demon- strated *, rose several thousand feet above the level of the Mediterranean, before the deposition of the recent Subapen- nine beds which flank them on either side. What now con- stitutes the central calcareous chain of the Apennines must for a long time have been a narrow ridgy peninsula, branching off at its northern extremity from the Alps near Savonna. A line of volcanos afterwards burst out in the sea, parallel to the * The greater number of Italian naturalists, and Brocchi among the rest, attri- buted the change of level to the lowering of the Mediterranean ; rejecting the more correct theory of Moro and his followers, that the land had been upheaved. 156 CHANGES OF THE SURFACE [Ch. VIII. axis of the older ridge. These igneous vents were extremely numerous, and the ruins of some of their cones and craters (as those in Tuscany, for example) indicate such a continued series of eruptions, almost all subsequent to the deposition of the Subapennine strata, that we cannot wonder at the vast changes in the relative level of land and sea which were pro- duced. However minute the effect of each earthquake which pre- ceded or intervened between such countless eruptions, the aggregate result of their elevating or depressing operation may well be expected to display itself in seas of great depth, and hills of considerable altitude. Accordingly, the more recent shelly beds, which often contain rounded pebbles derived from the waste of contiguous parts of the older Apennine rocks, have been raised from one to two thousand feet ; but they never attain the loftier eminences of the Apennines, nor pene- trate far into the higher and more ancient valleys; for the whole peninsula was evidently subjected to the action of the same subterranean movements, and the older and newer groups of strata changed their level, in relation to the sea, but not to each other. No. 1. Transverse Seel ion of the Italian Peninsula. In the above diagram, exhibiting a transverse section of the Italian peninsula, the superior elevation of the more ancient group, and its uncomformable stratification in relation to the more recent beds, is expressed. The latter, however, are often much more disturbed at the point of contact than is here repre- sented, and in some cases they have suffered such derangement as to dip towards, instead of from, the more ancient chain. CLIMATE CONTEMPORANEOUS. 157 There is usually, moreover, a valley at the junction of the Apenniue and Subapennine strata, owing to the greater degra- dation which the newer and softer beds have undergone ; but this intervening depression is not universal. These phenomena are exhibited in the Alps on a much grander scale; those mountains being encircled by a great zone of tertiary rocks of different ages, both on their southern flank towards the plains of the Po, and on the side of Switzer- land and Austria *, and at their eastern termination towards Styria and Hungary. This tertiary zone marks the position of former seas or gulfs, like the Adriatic, which were many thousand feet deep, and wherein strata accumulated, some single groups of which are not inferior in thickness to the whole of our secondary formations in England. These marine ter- tiary strata rise from the height of from two to four thousand feet and upwards, and consist of formations of different ages, characterized by different assemblages of organized fossils. The older tertiary groups generally rise to greater heights, and form ulterior zones nearest to the Alps. We may imagine some future convulsion once more to upraise this stupendous chain, together with the adjoining bed of the sea, so that the greatest mountains of Europe might rival the Andes in eleva- tion, in which case the deltas of the Po, Adige, and Brenta, now encroaching upon the Adriatic, might be uplifted so as to form another exterior belt of considerable height around the south-eastern flank of the Alps. Although we have not yet ascertained the number of different periods at which the Alps gained accessions to their height and width, yet we can affirm, that the last series of movements occurred when the seas were inhabited by many existing specie* of animals f . * See a Memoir by Professor Sedgwick and Mr. Mmduson, on the Tertiary Deposits of the Yak of Gosaa, in the Sakburg Alps, Proceedings of GeoL Soc. No. xiiL, Nor. 1829. + Brocchi supposed the Snhaprnninrbedt to occur fao^ffr on both ides of thepUinsoftheR>;bntmthbhe are for the most pan distinct and older etkal they km 158 CHANGES OF THE SURFACE [Ch. VIII. There appears to be no sedimentary formations in the Alps so ancient as the rocks of our carboniferous series ; while, on the other hand, secondary strata as modern as the green sand of English geologists, and perhaps the chalk, enter into some of the higher and central ridges. Down to the period, there- fore, when the rocks, from our lias to the chalk inclusive, were deposited, there was sea where now the principal chain of Europe extends, and that chain attained more than half its present elevation and breadth between the eras when our newer secondary and oldest tertiary rocks originated. The remainder of its growth, if we may so speak, is of much more recent date, some of the latest changes, as we have stated, having been coeval with the existence of many animals belong- ing to species now contemporary with man. The Pyrenees, also, have acquired the whole of their present altitude, which in Mont Perdu exceeds eleven thousand feet, since the origin of some of the newer members of our secondary series. The granitic axis of that chain does not rise so high as a ridge formed by marine calcareous beds, the organic remains of which show them to be the equivalents of our lower chalk, or a formation of about that age *. The tertiary strata at the base of this great chain are only slightly raised above the sea, and retain a horizontal position, without partaking of any of the disturbances to which the older series has been subjected, so that the great barrier between France and Spain was almost entirely upheaved in the interval between the deposition of the secondary and tertiary strata f. The Jura, also, owe the two districts only north of the Po. They form in these cases, as might have been anticipated, the outermost belt, as at Azolo. at the foot of the Alps near the plains of Venice, and at Bassano, on the Brenta. In the section given by Mr. Murchison of the strata laid open by the Brenta, between Bassano and the Alps above Cam- pese, it will be seen that the older chain must have partaken of the movement which raised the newest tertiary strata of the age of the Subapennines. Phil. Mag. and Annals, June, 1829. * This observation, first made by M. Boue, has been since confirmed by M. Dufrenoy. f See a Memoir by M. Elie de Beaumont, Ann. des Sci. Nat., Nov. 1829, p. 286. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 159 greatest part of their present elevation to subterranean con- vulsions which happened after the deposition of certain tertiary groups ; at which time that portion which had been previously raised above the level of the sea underwent an entire alteration of form *. In other parts of the continent, as in France and England, where the newer rocks lie in basins surrounded by gently- rising hills, we find evidence that considerable spaces were redeemed from the original ocean and converted into dry land after the chalk was formed, and before the origin of the ter- tiary deposits. In these cases, the secondary strata were not raised into lofty mountain -chains, like the Alps, Apennines, and Pyrenees, but the proofs are not less clear of their partial conversion into land anterior to the tertiary era. The chalk, for example, must have originated in the sea in the form of sediment from tranquil water ; but before the tertiary rocks of the Paris and London basins were deposited, large portions of it had been so raised as to be exposed to the destroying power of the elements. The layers of flint had been washed out by torrents and rivers from their cretaceous matrix, rounded by attrition, and transported to the sea, where oysters attached themselves, and in some localities grew to a full size, until covered by other beds of flint-pebbles or sand. These newer derivative deposits are found abundantly along the borders, and in the inferior strata of our tertiary basins, and they are often interstratified with lignite. We may fairly infer, that the various trees and plants which enter into the composition of this lignite, grew on the surface of the same chalk which was then wasting away, and affording to the torrents a con- stant supply of flint gravel. We cannot dwell longer on the distinct periods when the secondary and various tertiary groups were upraised, without anticipating details which belong to other parts of this treatise; but we may observe, that although geologists have neglected to point out the relation of changes in the configuration of the * M. Elie de Beaumont, Dec. 1829, p. 346. 160 CHANGES OF THE SURFACE [Ch. VIII. earth's surface with fluctuations in general temperature, they do not dispute the fact, that the sea covered the regions where a great part of the land in Europe is now placed, until after the period when the newer groups of secondary rocks were formed. There is, therefore, confessedly a marked coincidence in point of time between the greatest alteration in climate and the principal revolution in the physical geography of the northern hemisphere. It is very probable that the abruptness of the transition from the organic remains of the secondary to those of the tertiary epoch, may not be wholly ascribable to the present deficiency of our information. We shall doubtless hereafter discover many intermediate gradations, (and one of these may be recognized in the calcareous beds of Maastricht,) by which a passage was effected from one state of things to another ; but it is not impossible that the interval between the chalk and tertiary formations constituted an era in the earth's history, when the passage from one class of organic beings to another was, comparatively speaking, rapid. For if the doctrines ex- plained by us in regard to vicissitudes of temperature are sound, it will follow that changes of equal magnitude in the geographical features of the globe, may at different periods produce very unequal effects on climate; and, so far as the existence of certain animals and plants depends on climate, the duration of species may often be shortened or protracted, according to the rate at which the change in temperature proceeded. Let us suppose that the laws which regulate the subter- ranean forces are constant and uniform, (which we are entitled to assume, until some convincing proofs can be adduced to the contrary,) we may then infer, that a given amount of altera- tion in the superficial inequalities of the surface of the planet always requires for its consummation nearly equal periods of time. Let us then imagine the quantity of land between the equator and the tropic in one hemisphere to be to that in the other as thirteen to one, which, as we before stated, repre- Ch. VIII.] A * D CLIMATE CONTEMPORANEOUS. 161 sents the unequal proportion of the extra- tropical lands in the two hemispheres at present. Then let the first geographical change consist in the shifting of this preponderance of land from one side of the line to the other, from the southern hemi- sphere, for example, to the northern. Now this would not affect the general temperature of the earth. But if, at another epoch, we suppose a continuance of the same agenc}' to transfer an equal volume of land from the torrid zone to the temperate and arctic regions of the northern hemisphere, there might be so great a refrigeration of the mean temperature in all latitudes, that scarcely any of the pre-existing races of animals would survive, and, unless it pleased the Author of Nature that the planet should be uninhabited, new species would be substituted in the room of the extinct. We ought not, therefore, to infer, that equal periods of time are always attended by an equal amount of change in organic life, since a great fluctuation in the mean temperature of the earth, the most influential cause which can be conceived in exterminating whole races of animals and plants, must, in different epochs, require unequal portions of time for its completion. Maestricht beds. The only geological monument yet dis- covered, which throws light on the period immediately suc- ceeding the deposition of the chalk, is the series of calcareous beds in St. Peter's Mount at Maestricht. The turtles and gigantic reptiles there found, seem to indicate that the hot climate of the secondary era had not then been greatly modi- fied ; but as it seems that but a small proportion of the fossil species hitherto discovered are identical with known chalk fossils, there may, perhaps, have been a considerable lapse of ages between the consolidation of our upper chalk, and the completion of the Maestricht group*. During these ages, * It appears from a Memoir by Dr. Fitton, read before the Geological Society of London, Dec. 1829, that the Maestricht beds extend over a considerable area, preserving the same mineral characters and organic remains. Out of fifty species of shells and zoophytes collected by him, ten only could be identified with the copious list of chalk fossils published by Mr. Mantell, in the Geol. Trans., vol. iii. part 1, second series, p. 201. VOL. I. M 162 CHANGES OF THE SURFACE [Ch. VIII. part of the gradual rise of the Alps and Pyrenees may have been accomplished ; for we know that earthquakes may work mighty changes during what we may call a small portion of one zoological era, since there are hills in Sicily which have gained three thousand feet in height, while the assemblage of testacea and zoophytes inhabiting the Mediterranean has only suffered slight alterations, and a large part of the countries bordering the Mediterranean have been remodelled since about one-third of the existing species were in being. Theory of Central Heat. Before we conclude this chapter, we may be expected to offer some remarks on the gradual diminution of the supposed central heat of the globe, a doctrine which appears of late years to have increased in popularity. Baron Fourier, after making a curious series of experiments on the cooling of incandescent bodies, has endeavoured by pro- found mathematical calculations to prove that the actual dis- tribution of heat in the earth's envelope is precisely that which would have taken place if the globe had been formed in a medium of a very high temperature, and had afterwards been constantly cooled *. He supposes that the matter of our planet, as Leibnitz formerly conjectured, was in an intensely heated state at the era of its creation, and that the incandescent fluid nucleus has been parting ever since with portions of its original heat, thereby contracting its dimensions, a process which has not yet entirely ceased. But it is admitted, that there are no positive facts in support of this contraction ; on the contrary, La Place has shown, by reference to astronomical observations made in the time of Hipparchus, that in the last two thousand years there has been no sensible contraction of the globe by cooling down, for had this been the case, even to an extremely small amount, the day would have been shortened, whereas its length has certainly not diminished during that period by ^th of a second. The reader will bear in mind, that the question as to the See a Memoir on the Temperature of the Terrestrial Globe, and the Plane- tary Spaces, Ann, de Chimie et Phys., torn, xxvii. p. 135. Oct. 1824. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 163 existence of a central heat is very different from that of the gradual refrigeration of the interior of the earth. Many ob- servations and experiments appear to countenance the idea, that in descending from the surface to those slight depths to which man can penetrate, there is a progressive increase of heat; but if this be established, and if, as some are not afraid to infer, we dwell on a thin crust which covers a central ocean of liquid incandescent lava, we ought still to be very reluctant to con- cede on slight evidence that the internal heat is, or has been, variable in quantity. In our ignorance of the sources and nature of volcanic fire, it seems more consistent with philosophical caution, to assume that there is no instability in this part of the terrestrial system. We know that different regions have been subject in succession to a series of violent subterranean convulsions, and that fissures have opened from which hot vapours, thermal springs, and, at some points, red hot liquid lavas have issued to the surface. This evolution of heat often continues for ages after the ex- tinction of volcanos and after the cessation of earthquakes, as in Central France, for example, and it seems perfectly natural, that each part of the earth's crust should, as M. Fourier states to be the fact, present the appearance of a heated body slowly cooling down. This may be owing to the former universality of the volcanic foci now shifted ; but some effect may perhaps be due to that unequal absorption of the solar rays to which we have alluded, when speaking of the different temperature of the earth, according to the varying distribution of its super- ficial inequalities. M. Cordier announces as the result of his experiments and observations on the temperature of the interior of the earth, that the heat increases rapidly with the depth, but the increase does not follow the same law over the whole earth, being twice or three times as much in one country as in another, and these differences not being in constant relation either with the lati- tudes or longitudes of places. All this is precisely what we should have expected to arise from variations in the intensity M 2 161 CHANGES OF THE SURFACE [Ch. VIII. of volcanic heat, and from that change of position, which the principal theatres of volcanic action have undergone at different periods, as the geologist can distinctly prove. But M. Cordier conjectures that there is a connexion between such phenomena and the secular refrigeration and contraction of the internal fluid mass, and that the changes of climate, of which there are geological proofs, favour this hypothesis *. We cannot help suspecting that if it had appeared that the same species of animals and plants had continued to inhabit the seas, lakes, and continents, before and after the great physical mutations which the northern hemisphere has undergone since the secondary strata were formed, the difficulty of explaining the ancient climate of the globe would have appeared far more insurmountable than at present. It would have been so con- trary to the elementary truths of meteorology to suppose no refrigeration to have followed from the rising of so many new mountain-chains in northern latitudes,, that recourse would probably have been had in that case also to cosmological specu- lations. It might have been argued with much plausibility, that as the accession of high ridges covered with perpetual snow and glaciers had not occasioned any perceptible increase of cold, so as to affect the state of organic life, there must have been some new source of heat which counterbalanced that refrigerating cause. This, it might have been said, was the increased development of central fire issuing from innumerable fissures opened in the crust of the earth, when it was shaken by convulsions which raised the Alps and other colossal chains. But, without entering into further discussion on the merits of the hypothesis of gradual refrigeration, let us hope that ex- periments will continue to be made, to ascertain whether there be internal heat in the globe, and what laws may govern its distribution. When its existence has been incontrovertibly established, it will be time to inquire whether it be subject to * See M. Cordier's Memoir on the Temperature of the Interior of the Earth, read to the Academy of Sciences, 4th June, 1827. Edin. New Phil. Journ. No. viii. p. 273. Ch. VIII.] AND CLIMATE CONTEMPORANEOUS. 165 secular variations. Should these also be confirmed, we may begin to indulge speculations respecting the cause, but let us not hastily assume that it has reference to the original forma- tion of the planet, with which it might be as unconnected as with its final dissolution. In the mean time we know that great changes in the external configuration of the earth's crust have at various times taken place, and we may affirm that they must have produced some effect on climate. The extent of their influence ought, there- fore, to form a primary object of inquiry, more especially as there seems an obvious coincidence between the eras at which the principal accessions of land in high latitudes were made, and the successive periods when the diminution of temperature was most decided. CHAPTER IX. Further discussion of the question as to the discordance of the ancient and mo- dern causes of change Theory of the progressive development of organic life Evidence in its support wholly inconclusive Vertebrated animals in the oldest strata Differences between the organic remains of successive formations Remarks on the comparatively modern origin of the human race The popular doctrine of successive development not confirmed by the admission that man is of modern origin Introduction of man, to what extent a change in the system. THEORY OF THE PROGRESSIVE DEVELOPMENT OF ORGANIC LIFE. WE have considered, in the preceding chapters, many of the most popular grounds of opposition to the doctrine, that all former changes of the organic and inorganic creation are re- ferrible to one uninterrupted succession of physical events, governed by the laws now in operation. As the principles of the science must always remain unset- tled so long as no fixed opinions are entertained on this fun- damental question, we shall proceed to examine other objections which have been urged against the assumption of uniformity in the order of nature. We shall cite the words of a late dis- tinguished writer, who has formally advanced some of the weightiest of these objections. ' It is impossible,' he affirms,, ' to defend the proposition, that the present order of things is the ancient and constant order of nature, only modified by ex- isting laws in those strata which are deepest, and which must, consequently, be supposed to be the earliest deposited, forms even of vegetable life are rare ; shells and vegetable remains are found in the next order ; the bones of fishes and oviparous reptiles exist in the following class ; the remains of birds, with those of the same genera mentioned before, in the next order ; those of quadrupeds of extinct species in a still more recent class ; and it is only in the loose and slightly-consolidated strata Ch. IX.] UNIFORMITY OF PHYSICAL LAWS. 167 of gravel and sand, and which are usually called diluvian for- mations, that the remains of animals such as now people the globe are found, with others belonging to extinct species. But, in none of these formations, whether called secondary, tertiary, or diluvial, have the remains of man, or any of his works, been discovered ; and whoever dwells upon this subject must be convinced, that the present order of things, and the compara- tively recent existence of man as the master of the globe, is as certain as the destruction of a former and a different order, and the extinction of a number of living forms which have no types in being. In the oldest secondary strata there are no remains of such animals as now belong to the surface ; and in the rocks, which may be regarded as more recently deposited, these re- mains occur but rarely, and with abundance of extinct species ; there seems, as it were, a gradual approach to the present system of things, and a succession of destructions and creations preparatory to the existence of man *.' In the above passages, the author deduces two important conclusions from geological data : first, that in the successive groups of strata, from the oldest to the most recent, there is a progressive development of organic life, from the simplest to the most complicated forms ; secondly, that man is of com- paratively recent origin. It will be easy to show that the first of these propositions, though very generally received, has no foundation in fact. The second, on the contrary, is indis- putable, and it is important, therefore, to consider how far its admission is inconsistent with the assumption, that the system of the natural world has been uniform from the beginning, or rather from the era when the oldest rocks hitherto discovered were formed. We shall first examine the geological proofs appealed to in support of the theory of the successive development of animal and vegetable life, and their progressive advancement to a more perfect state. No geologists, who are in possession of all the data now established respecting fossil remains, will for a * Sir H. Davy, Consolations in Travel, Dialogue III., ' The Unknown.' 168 THEORY OF [Ch. IX. moment contend for the doctrine in all its detail, as laid down by the great chemist to whose opinions we have referred. But naturalists, who are not unacquainted with recent discoveries, continue to defend the ancient doctrine in a somewhat modified form. They say that, in the first period of the world, (by which they mean the earliest of which we have yet procured any memorials,) the vegetation consisted almost entirely of cryptogamic plants, while the animals which co-existed were almost entirely confined to zoophytes, testacea, and a few fish. Plants of a less simple structure succeeded in the next epoch, when oviparous reptiles began also to abound. Lastly, the ter- restrial flora became most diversified and most perfect when the highest orders of animals, the mammifera and birds, were called into existence. Now, in the first place, we may observe, that many naturalists have been guilty of no small inconsistency in endeavouring to connect the phenomena of the earliest vegetation with a nascent condition of organic life, and at the same time to deduce, from the numerical predominance of certain types of form, the greater heat of the ancient climate. The arguments in favour of the latter conclusion are without any force, unless we can assume that the rules followed by the Author of Nature in the creation and distribution of organic beings were the same formerly as now ; and that as certain families of animals and plants are now most abundant, or exclusively confined to regions where there is a certain temperature, a certain degree of humidity, a certain intensity of light, and other conditions, so also the same phenomena were exhibited at every former era. If this postulate be denied, and the prevalence of particular families be declared to depend on a certain order of precedence in the introduction of different classes into the earth, and if it be maintained that the standard of organization was raised successively, we must then ascribe the numerical preponder- ance in the earlier ages of plants of simpler structure, not to the heat, but to those different laws which regulate organic life in newly-created worlds. If, according to the laws of pro- Ch ix.] SUCCESSIVE DEVELOPMENT. 169 gressive development, cryptogamic plants always flourish for ages before the dicotyledonous order can be established, then is the small proportion of the latter fully explained ; for in this case, whatever may have been the mildness or severity of the climate, they could not make their appearance. Before we can infer an elevated temperature in high lati- tudes, from the presence of arborescent Ferns, Lycopodiacese, and other allied families, we must be permitted to assume, that at all times, past and future, a heated and moist atmo- sphere pervading the northern hemisphere has a tendency to produce in the vegetation a predominance of analogous types of form. We grant, indeed, that there may be a con- nexion between an extraordinary profusion of monocotyledo- nous plants and a youthful condition of the world, if the dogma of certain cosmogonists be true, that planets, like certain pro- jectiles, are always red hot when they are first cast ; but to this arbitrary hypothesis, against which we have already protested, we need not again revert. Between two and three hundred species of plants are now enumerated as belonging to the carboniferous era, and of these a very few only are dicotyledonous*. But these exceptions are as fatal to the doctrine of successive development as if there were a thousand, although they do not by any means invalidate the conclusion in regard to the heat of the ancient climate, for that depends on the numerical relations of the dif- ferent classes. Vertebrated animals in the oldest strata. The animal remains in the most ancient series of European sedimentary rocks (from the gray wacke to the coal inclusive), consist chiefly * Fragments of dicotyledonous wood, which have evidently belonged to at least two different species of trees, have been obtained from the coal-field of Fife, by Dr. Fleming, of Flisk, and the same gentleman has shown me a large dicotyle- donous stem which he procured from the graywacke of Cork. See a memoir by Dr. Fleming on the neighbourhood of Cork. (Trans, of Wern. Soc. Edin.) I am informed also by Dr. Buckland, that he has received from the coal-field of North- umberland another specimen of dicotyledonous wood, which is now in the Oxford Museum. 170 THEORY OF [Ch. IX. of corals and testacea. Some estimate may generally be formed of the comparative extent of our information con- cerning the fossil remains of a particular era, by reference to the number of species of shells obtained from a particular group of strata. Some of the rarest species cannot be dis- covered, unless the more abundant kinds have been found again and again ; and if the variety brought to light be very considerable, it proves not only great diligence of research, but a good state of preservation of the organic contents of that formation. In the older rocks, many causes of destruction have operated, of which the influence has been rendered con- siderable by the immense lapse of ages during which they have acted. Mechanical pressure, derangement by subterranean movements, the action of chemical affinity, the percolation of acidulous waters and other agencies, have obliterated, in a greater or less degree, all traces of organization in fossil bodies. Sometimes only obscure or unintelligible impressions are left, and the lapidifying process has often effaced not only the cha- racters by which the species, but even those whereby the class might be determined. The number of organic forms which have disappeared from the oldest strata, may be conjectured from the fact, that their former existence is in many cases merely revealed to us by the unequal weathering of an exposed face of rock, by which cer- tain parts are made to stand out in relief. As the number of species of shells found in the English series, from the gray- wacke to the coal inclusive, after attentive examination, amounts only to between one and two hundred, we cannot be surprised that so few examples of vertebrated animals have as yet oc- curred. The remains of fish, however, appear in one of the lowest members of the group. Numerous scales of fish have been found by Dr. Fleming in quarries of the old red sand- stone at Clashbinnie in Perthshire, where I have myself col- lected them. These beds are decidedly older than the coal and mountain limestone of Fifeshire, which entirely destroys the theory of the precedence of the simplest forms of animals. Ch. IX] SUCCESSIVE DEVELOPMENT. 171 Scales also of a tortoise nearly allied to trionyx occur abun- dantly in the bituminous schists of Caithness, and in the same formation in the Orkneys in Scotland. Professor Sedgwick and Mr. Murchison confidently pronounce these schists to be of the age of the old red sandstone ; so that we have here an example of a fossil reptile in rocks belonging to the oldest part of the carboniferous series *. The only negative fact, therefore, remaining in support of the doctrine of the imperfect development of the higher orders of animals in remote ages, is the absence of birds and mam- malia. The former are generally wanting in deposits of all ages, even where the highest order of animals occurs in abun- dance. Land mammifera could not, as we have before sug- gested, be looked for in strata formed in an ocean interspersed with isles, such as we must suppose to have existed in the northern hemisphere, when the carboniferous rocks were formed. As all are agreed that the ancient strata in question were subaqueous, and for the most part submarine, from what data, we may ask, do naturalists infer the non-existence or even the rarity of warm-blooded quadrupeds in the earlier ages ? Have they dredged the bottom of the ocean throughout an area co- extensive with that now occupied by the carboniferous rocks, and have they found that with the number of between one and two hundred species of shells they always obtain the remains of at least one land quadruped ? Suppose our mariners were to report that on sounding in the Indian ocean near some coral reefs, and at some distance from the land, they drew up on hooks attached to their line portions of a leopard, elephant, or tapir ; should we not be sceptical as to the accuracy of their state- ments ; and if we had no doubt of their veracity, might we not suspect them to be unskilful naturalists ? or, if the fact were unquestioned, should we not be disposed to believe that some vessel had been wrecked on the spot ? * See Geol. Trans., second series, vol. iii. part 1, p. 144, and for a representa- tion of the scales of the Trionyx, plate 16 of the same part. 172 THEORY OF [Ch. IX. The casualties must be rare indeed whereby land quadru- peds are swept by rivers and torrents into the sea, and still rarer must be the contingency of such a floating body not being devoured by sharks or other predaceous fish, such as were those of which we find the teeth preserved in some of the car- boniferous strata*. But if the carcass should escape, and should happen to sink where sediment was in the act of accu- mulating, and if the numerous causes of subsequent disinte- gration should not efface all traces of the body included for countless ages in solid rock, is it not contrary to all calcula- tion of chances that we should hit upon the exact spot, that mere point in the bed of the ancient ocean, where the precious relic was entombed ? Can we expect for a moment that when we have only succeeded amidst several thousand fragments of corals and shells, in finding a few bones of aquatic or amphibious animals, that we should meet with a single skeleton of an inha- bitant of the land ? Clarence, in his dream, saw ' in the slimy bottom of the deep/ a thousand fearful wrecks ; A thousand men, that fishes gnaw'd upon ; Wedges of gold, great anchors, heaps of pearl. Had he also beheld amid ( the dead bones that lay scattered by/ the carcasses of lions, deer, and the other wild tenants of the forest and the plain, the fiction would have been deemed unworthy of the genius of Shakspeare. So daring a disregard of probability, so avowed a violation of analogy, would have been condemned as unpardonable even where the poet was painting those incongruous images which present themselves to a disturbed imagination during the visions of the night. But the cosmogonist is not amenable, even in his waking hours, to these laws of criticism ; for he assumes either that the order of nature was formerly different, or that the globe was in a con- dition to which it can never again be reduced by changes which the existing laws of nature can bring about. This * I have seen in the collection of Dr. Fleming, the teeth of carnivorous fish from the mountain limestone of Fife, which alternates with the coal. Ch. IX.] SUCCESSIVE DEVELOPMENT. 173 assumption being once admitted, inexplicable anomalies and violations of analogy, instead of offending his judgment, give greater consistency to his reveries. Organic remains of the Secondary strata. The organic contents of the secondary strata in general consist of corals and marine shells. Of the latter, the British strata (from the inferior oolite to the chalk inclusive) have yielded about six hundred species. Vertebrated animals are very abundant, but they are almost entirely confined to fish and reptiles. But some remains of cetacea have also been met with in the oolitic series of England *, and the bones of two species of warm- blooded quadrupeds of extinct genera allied to the Opossum f. The occurrence of one individual of the higher classes of mam- malia, whether marine or terrestrial, in these ancient strata, is as fatal to the theory of successive development, as if several hundreds had been discovered. Of the Tertiary strata. The tertiary strata, as will appear from what we have already stated, were deposited when the physical geography of the northern hemisphere had been en- tirely altered. Large inland lakes had become numerous, as in Central France and many other countries. There were gulfs of the sea, into which large rivers emptied themselves, where strata were formed like those of the Paris basin. There were then also littoral formations in progress, such as are indi- cated by the English Crag, and the Faluns of the Loire. The state of preservation of the organic remains of this period is very different from that of fossils in the older rocks, the colours * On the authority of Dr. Buckland. Trans. Geol. Soc. vol. i. part 2, second series, p. 394. f The mammiferous remains of the Stonesfield slate, near Oxford, consist of three or perhaps four jaws, one of which, now in the Oxford Museum, has been examined by M. Cuvier, and pronounced to belong to a species of Didelphis. Another of these valuable fossils, in the possession of my friend Mr. Broderip, appears to be not only specifically, but generically distinct, from that shown to M. Cuvier. See Observations on the Jaw of a fossil Mammiferous Animal found in the Stouesfield Slate, by W. J. Broderip, Esq., Sec. G.S., F.R.S., F.L.S., &c., Zool. Journ., vol. iii., p. 408 , 1827. 174 THEORY OF [Ch. IX. of the shells, and even the cartilaginous ligaments uniting the valves being in some cases retained. No less than 1122 species of testacea have been found in the beds of the Paris basin,, and an equal number in the more modern formations of the Sub- apennine hills ; and it is a most curious fact in natural history, that the zoologist has already acquired more extensive informa- tion concerning the testacea which inhabited the ancient seas of northern latitudes at that era, than of those now living in the same parallels in Europe. Paris basin. The strata of the Paris basin are partly of fresh-water origin, and filled with the spoils of the land. They have afforded a great number of skeletons of land qua- drupeds, but these relics are confined almost entirely to one small member of the group, and their conservation may be considered as having arisen from some local and accidental combination of circumstances. On the other hand, the scarcity of terrestrial mammalia in submarine sediment is elucidated, in a striking manner, by the extremely small number of such remains hitherto procured from the Subapennine hills. The facilities of investigation in these strata, which undergo rapid degradation by rivers and streamlets, are, perhaps, unexampled in the rest of Europe, and they have been examined by col- lectors for three hundred years. But although they have already yielded twelve hundred species of testacea, the authenticated examples of associated remains of terrestrial mammalia are extremely scanty; and several of those which have been cited by earlier writers as belonging to the elephant or rhinoceros, have since been declared, by able anatomists, to be the bones of whales and other cetacea. In about five or ten instances, perhaps, bones of the mastodon, rhinoceros, and some other animals, have been observed in this formation with marine shells attached. These must have been washed into the bed of the ancient sea when the strata were forming, and they serve to attest the contiguity of land inhabited by large herbivora, which renders the rarity of such exceptions more worthy of atten- C'h. IX.] SUCCESSIVE DEVELOPMENT. 175 tion. On the contrary, the number of skeletons of existing animals in the upper Val d'Arno, which are usually consi- dered to be referrible to the same age as the Subapennine beds, occur in a deposit which was formed entirely in an inland lake, surrounded by lofty mountains. London clay Plastic clay. The inferior member of our oldest tertiary formations in England, usually termed the plastic clay, has hitherto proved as destitute of mammiferous remains, as our ancient coal strata ; and this point of resem- blance between these deposits is the more worthy of observa- tion, because the lignite, in the one case, and the coal in the other, are exclusively composed of terrestrial plants. From the London clay we have procured three or four hundred species of testacea, but the only bones of vertebrated animals are those of reptiles and fish. On comparing, therefore, the contents of these strata with those of our oolitic series, we find the supposed order of precedence inverted. In the more ancient system of rocks, mammalia^ both of the land and sea, have been recognized, whereas in the newer, if negative evi- dence is to be our criterion, nature has made a retrograde, instead of a progressive, movement, and no animals more ex- alted in the scale of organization than reptiles are discoverable. In a fresh -water formation, however, resting upon the London clay, in the Isle of Wight, probably referrible to about the same epoch, some mammiferous remains have been found *. Not a single bone of a quadrumanous animal has ever yet been discovered in a fossil state, and their absence has appeared, to some geologists, to countenance the idea that the type of organization most nearly resembling the human came last in the order of creation, and was scarcely perhaps anterior to that of man. But the evidence on this point is quite inconclusive, for we know nothing, as yet, of the details of the various classes of the animal kingdom which inhabited the land up to the consolidation of the newest of the secondary strata ; and * Bucklaud and Allan, Jameson's Ed. Phil. Journ. No. 27. p. 190. Pratt, Proceedings of Geol. Soc. No. 18, 1831. 176 THEORY OF [Ch. IX. \vhen the newest tertiary formations were in progress, the cli- mate does not appear to have been of such a tropical character as seems necessary for the development of the tribe of apes, monkeys, and allied genera. Besides, it must not be forgotten, that almost all the animals which occur in subaqueous deposits are such as frequent marshes, rivers, or the borders of lakes, as the rhinoceros, tapir, hippopotamus, ox, deer, pig, and others. On the other hand, species which live in trees are extremely rare in a fossil state, and we have no data as yet for determin- ing how great a number of the one kind we ought to find, before we have a right to expect a single individual of the other. If, therefore, we are led to infer, from the presence of crocodiles and turtles in the London clay, and from the cocoa- nuts and spices found in the Isle of Sheppey, that at the period when our older tertiary strata were formed, the climate was hot enough for the quadrumanous tribe, we nevertheless could not hope to discover any of their skeletons until we had made considerable progress in ascertaining what were the contempo- rary Pachydermata ; and not one of these, as we have already remarked, has been discovered as yet in any of the marine strata of this epoch in England. Recent origin of man. It is therefore clear that there is no foundation in geological facts for the popular theory of the successive development of the animal and vegetable world, from the simplest to the most perfect forms ; and we shall now proceed to consider another question, whether the recent origin of man lends any support to the same doctrine, or how far the influence of man may be considered as such a deviation from the analogy of the order of things previously established, as to weaken our confidence in the uniformity of the course of nature. We need not dwell on the proofs of the low antiquity of our species, for it is not controverted by any geologist ; indeed, the real difficulty which we experience consists in tracing back the signs of man's existence on the earth to that comparatively modern period when species, now his contemporaries, began to Ch. IX.] SUCCESSIVE DEVELOPMENT. 177 predominate. If there be a difference of opinion respecting the occurrence in certain deposits of the remains of man and his works, it is always in reference to strata confessedly of the most modern order ; and it is never pretended that our race co-existed with assemblages of animals and plants, of which all the species are extinct. From the concurrent testimony of history and tradition, we learn that parts of Europe, now the most fertile and most completely subjected to the dominion of man,, were, less than three thousand years ago, covered with forests, the abode of wild beasts. The archives of nature are in perfect accordance with historical records ; and when we lay open the most superficial covering of peat, we sometimes find therein the canoes of the savage, together with huge antlers of the wild stag, or horns of the wild bull. In caves now open to the day in various parts of Europe, the bones of large beasts of prey occur in abundance ; and they indicate that, at periods extremely modern in the history of the globe, the ascendency of man, if he existed at all, had scarcely been felt by the brutes *. No inhabitant of the land exposes himself to so many dan- gers on the waters as man, whether in a savage or a civilized 'state, and there is no animal, therefore, whose skeleton is so liable to become imbedded in lacustrine or submarine deposits j nor can it be said that his remains are more perishable than those of other animals, for in ancient fields of battle, as Cuvier has observed, the bones of men have suffered as little decom- position as those of horses which were buried in the same grave. But even if the more solid parts of our species had disappeared, the impression would have remained engraven on the rocks, as have the traces of the tenderest leaves of plants, and the integuments of many animals. Works of art, more- over, composed of the most indestructible materials, would * We shall discuss in the next volume, when treating of animal remains in caves, the probahle antiquity assignable to certain human bones and works of art found intermixed with remains of extinct animals in the cavern of Bize, and in several localities in the department of Herault, iu France. VOL. I. N 178 UNIFORMITY OF THE SYSTEM. [Ch. IX have outlasted almost all the organic contents of sedimentary rocks ; edifices, and even entire cities, have, within the times of history, been buried under volcanic ejections, or submerged beneath the sea, or engulphed by earthquakes ; and had these catastrophes been repeated throughout an indefinite lapse of ages, the high antiquity of man would have been inscribed in far more legible characters on the framework of the globe than are the forms of the ancient vegetation which once covered the isles of the northern ocean, or of those gigantic reptiles which at later periods peopled the seas and rivers of the northern hemisphere. Dr. Prichard k has argued that the human race have not always existed on the surface of the earth, because ' the strata of which our continents are composed were once a part of the ocean's bed' ( mankind had a beginning, since we can look back to the period when the surface on which they lived began to exist *.' This proof however is insufficient, for many thou- sands of human beings now dwell in various quarters of the globe where marine species lived within the times of history, and, on the other hand, the sea now prevails permanently over large districts once inhabited by thousands of human beings. Nor can this interchange of sea and land ever cease while the present causes are in existence. A terrestrial species, there- fore, may be older than the continents which it inhabits, aquatic animals and plants of higher antiquity than the lakes and seas which they people. It is on other grounds that we feel entitled to infer that man is, comparatively speaking, of modern origin ; and, if this be assumed, we may ask whether his introduction can be consi- dered as one step in a progressive system by which, as some suppose, the organic world advanced slowly from a more sim- ple to a more perfect state ? Doctrine of successive development, not confirmed by the ad- mission, that man is of modern origin. To this question we may reply, that the superiority of man depends not on those * Phys. Hist, of Mankind, vol. ii. p. 594. Ch. IX.] RECENT ORIGIN OF MAN. 179 faculties and attributes which he shares in common with the inferior animals, but on his reason, by which he is distinguished from them. If the organization of man were such as would confer a decided pre-eminence upon him, even if he were deprived of his reasoning powers, and provided only with such instincts as are possessed by the lower animals, he might then be supposed to be a link in a progressive chain, especially if it could be shown that the successive development of the ani- mal creation had always proceeded from the more simple to the more compound, from species most remote from the human type to those most nearly approaching to it. But this is an hypothesis which, as we have seen, is wholly unsupported by geological evidence. On the other hand, we may admit that man is of higher dignity than were any pre-existing beings on the earth, and yet question whether his coming was a step in the gradual advancement of the organic world : for the most highly civilized people may sometimes degenerate in strength and stature, and become inferior in their physical attributes to the stock of rude hunters from which they descended. If then the physical organization of man may remain stationary, or even become deteriorated, while the race makes the greatest progress to higher rank and power in the scale of rational being, the animal creation also may be supposed to have made no progress by the addition to it of the human species, regarded merely as a part of the organic world. But, if this reasoning appear too metaphysical, let us waive the argument altogether, and grant that the animal nature of man, even considered apart from the intellectual, is of higher dignity than that of any other species ; still the introduction at a certain period of our race upon the earth raises no presump- tion whatever that each former exertion of creative power was characterized by the successive development of irrational ani- mals of higher orders. The comparison here instituted is between things so dissimilar, that when we attempt to draw such inferences, we strain analogy beyond all reasonable bounds. We may easily conceive that there was a considerable departure N 2 180 UNIFORMITY OF THE SYSTEM. [Ch. IX from the succession of phenomena previously exhibited in the organic world, when so new and extraordinary a circumstance arose, as the union, for the first time, of moral and intellectual faculties capable of indefinite improvement, with the animal nature. But we have no right to expect that there were any similar deviations from analogy any corresponding steps in a progressive scheme, at former periods, when no similar circum- stances occurred. Introduction of man to tvhat extent a change in the system. But another and a far more difficult question may arise out of the admission that man is comparatively of modern origin. Is not the interference of the humart species, it may be asked, such a deviation from the antecedent course of physical events, that the knowledge of such a fact tends to destroy all our con- fidence in the uniformity of the order of nature, both in regard to time past and future ? If such an innovation could take place after the earth had been exclusively inhabited for thou- sands of ages by inferior animals, why should not other changes as extraordinary and unprecedented happen from time to time ? If one new cause was permitted to supervene, differing in kind and energy from any before in operation, why may not others have come into action at different epochs? Or what security have we that they may not arise hereafter ? If such be the case, how can the experience of one period, even though we are acquainted with all the possible effects of the then existing causes, be a standard to which we can refer all natural pheno- mena of other periods ? Now these objections would be unanswerable, if adduced against one who was contending for the absolute uniformity throughout all time of the succession of sublunary events if, for example, he was disposed to indulge in the philosophical reveries of some Egyptian and Greek sects, who represented all the changes both of the moral and material world as re- peated at distant intervals, so as to follow each other in their former connexion of place and time. For they compared the course of events on our globe to astronomical cycles, and not Ch. IX. 1 RECENT ORIGIN OF MAN. 181 only did they consider all sublunary affairs to be under the influence of the celestial bodies, but they taught that on the earth, as well as in the heavens, the same identical phenomena recurred again and again in a perpetual vicissitude. The same individual men were doomed to be re-born, and to perform the same actions as before ; the same arts were to be invented, and the same cities built and destroyed. The Argonautic expedi- tion was destined to sail again with the same heroes, and Achilles with his myrmidons, to renew the combat before the walls of Troy. Alter erit turn Tiphys et altera quae vehat Argo Dilectos heroas ; erunt etiam altera bella, Atque iterum ad Trojam inagnus mittetur Achilles *. The geologist, however, may condemn these tenets as absurd, without running into the opposite extreme, and denying that the order of nature has, from the earliest periods, been uniform in the same sense in which we believe it to be uniform at pre- sent. We have no reason to suppose, that when man first be- came master of a small part of the globe, a greater change took place in its physical condition than is now experienced when districts, never before inhabited, become successively occupied by new settlers. When a powerful European colony lands on the shores of Australia, and introduces at once those arts which it has required many centuries to mature ; when it imports a multitude of plants and large animals from the oppo- site extremity of the earth, and begins rapidly to extirpate many of the indigenous species, a mightier revolution is effected in a brief period, than the first entrance of a savage horde, or their continued occupation of the country for many centuries, can possibly be imagined to have produced. If there be no impropriety in assuming that the system is uniform when dis- turbances so unprecedented occur in certain localities, we can with much greater^confidence apply the same language to those primeval ages when the aggregate number and power of the * Virgil, Eclog. iv. For an account of these doctrines, see Dugald Stewart's Elements of the Philosophy of the Human Mind, vol. ii. chap. ii. sect. 4, and Prichard's Egypt. Mythol. p. 177. 182 UNIFORMITY OF THE SYSTEM. [Ch. IX. human race, or the rate of their advancement in civilization, must be supposed to have been far inferior. If the barren soil around Sidney had at once become fertile upon the landing of our first settlers ; if, like the happy isles whereof the poets have given us such glowing descriptions, those sandy tracts had begun to yield spontaneously an annual supply of grain, we might then, indeed, have fancied alterations still more remarkable in the economy of nature to have attended the first coming of our species into the planet. Or if, when a volcanic island like Ischia was, for the first time, brought under cultivation by the enterprise and industry of a Greek colony, the internal fire had become dormant, and the earth- quake had remitted its destructive violence, there would then have been some ground for speculating on the debilitation of the subterranean forces, when the earth was first placed under the dominion of man. But after a long interval of rest, the volcano bursts forth again with renewed energy, annihilates one half of the inhabitants, and compels the remainder to emigrate. Such exiles, like the modern natives of Cumana, Calabria, Sumbawa, and other districts, habitually convulsed by earth- quakes, would probably form no very exalted estimate of the sagacity of those geological theorists, who, contrasting the human with antecedent epochs, have characterized it as the period of repose. In reasoning on the state of the globe immediately before our species was called into existence, we may assume that all the present causes were in operation, with the exception of man, until some geological arguments can be adduced to the con- trary. We must be guided by the same rules of induction as when we speculate on the state of America in the interval that elapsed between the period of the introduction of man into Asia, the cradle of our race, and that of the arrival of the first adventurers on the shores of the New World. In that interval, we imagine the state of things to have gone on according to the order now observed in regions unoccupied by man. Even now, the waters of lakes, seas, and the great ocean, which teem with Ch. IX.] RECENT ORIGIN OF MAN. 183 life, may be said to have no immediate relation to the human race to be portions of the terrestrial system of which man has never taken, nor ever can take, possession ; so that the greater part of the inhabited surface of the planet remains still as in- sensible to our presence, as before any isle or continent was appointed to be our residence. The variations in the external configuration of the earth, and the successive changes in the races of animals and plants in- habiting the land and sea, which the geologist beholds when he restores in imagination the scenes presented by certain regions at former periods, are not more full of wonderful or inexpli- cable phenomena, than are those which a traveller would wit- ness who traversed the globe from pole to pole. Or if there be more to astonish and perplex us in searching the records of the past, it is because one district may, in an indefinite lapse of ages, become the theatre of a greater number of extraordinary events, than the whole face of the globe can exhibit at one time. However great the multiplicity of new appearances, and however unexpected the aspect of things in different parts of the present surface, the observer would never imagine that he was transported from one system of things to another, because there would always be too many points of resemblance, and too much connexion between the characteristic features of each country visited in succession, to permit any doubt to arise as to the continuity and identity of the whole plan. 6 In our globe,' says Paley, new countries are continually 1 discovered, but the old laws of nature are always found in ( them : new plants perhaps, or animals, but always in com- ( pany with plants and animals which we already know, and ' always possessing many of the same general properties. We 1 never get amongst such original, or totally different modes of e existence as to indicate that we are come into the province of ' a different Creator, or under the direction of a different will. 6 In truth, the same order of things attends us wherever we ' go*.' But the geologist is in danger of drawing a contrary * Natural Theology, chap. xxv. 184 UNIFORMITY OF THE SYSTEM. [Ch. IX. inference, because he has the power of passing rapidly from the events of one period to those of another of beholding, at one glance, the effects of causes which may have happened at intervals of time incalculably remote, and during which, never- theless, no local circumstances may have occurred to mark that there is a great chasm in the chronological series of nature's archives. In the vast interval of time which may really have elapsed between the results of operations thus compared, the physical condition of the earth may, by slow and insensible modifications, have become entirely altered ; one or more races of organic beings may have passed away, and yet have left behind, in the particular region under contemplation, no trace of their existence. To a mind unconscious of these interme- diate links in the chain of events, the passage from one state of things to another must appear so violent, that the idea of revolutions in the system inevitably suggests itself. The imagination is as much perplexed by such errors, as to time, as it would be if we could annihilate space, and by some power, such as we read of in tales of enchantment, could transfer a person who had laid himself down to sleep in a snowy arctic wilderness, to a valley in a tropical region, where, on awaking, he would find himself surrounded by birds of brilliant plumage, and all the luxuriance of animal and vegetable forms of which nature is there so prodigal. The most reasonable supposition, perhaps, which a philosopher could make, if by the necro- mancer's art he was placed in such a situation, would be, that he was dreaming ; and if a geologist forms theories under a similar delusion, we should not expect him to preserve more consistency in his speculations, than in the train of ideas in an ordinary dream. But if, instead of inverting the natural order of inquiry, we cautiously proceed in our investigations, from the known to the unknown, and begin by studying the most modern periods of the earth's history, attempting afterwards to decipher the mo- numents of more ancient changes, we can never so far lose sight of analogy, as to suspect that we have arrived at a new Ch jx.] RECENT ORIGIN OF MAN. 185 system, governed by different physical laws. In more recent formations, consisting often of strata of great thickness, the shells of the present seas and lakes, and the remains of animals and plants now living on the land, are imbedded in great num- bers. In those of more ancient date, many of the same species are found associated with others now extinct. These unknown kinds again are observed in strata of still higher antiquity, con- nected with a great number of others which have also no living representatives, till at length we arrive at periods of which the monuments contain exclusively the remains of species with many genera foreign to the present creation. But even in the oldest rocks which contain organic remains, some genera of marine animals are recognized, of which species still exist in our seas, and these are repeated at different inter- vals in all the intermediate groups of strata, attesting that, amidst the great variety of revolutions of which the earth's surface has been the theatre, there has never been a departure from the conditions necessary for the existence of certain unal- tered types of organization. The uniformity of animal instinct, observes Mr. Stewart *, pre-supposes a corresponding regula- rity in the physical laws of the universe, ' insomuch that if the established order of the material world were to be essentially disturbed, (the instincts of the brutes remaining the same,) all their various tribes would inevitably perish.' Now, any naturalist will be convinced, on slight reflection, of the justice of this remark. He will also admit that the same species have always retained the same instincts, and, therefore, that all the strata wherein any of their remains occur, must have been formed when the phenomena of inanimate matter were the same as they are in the actual condition of the earth. The same conclusion must also be extended to the extinct animals with which the remains of these living species are associated; and by these means we are enabled to establish the permanence of the existing physical laws, throughout the whole period when the tertiary deposits were formed. We have * Phil, of the Human Mind, vol. ii. p. 230. 186 UNIFORMITY OF THE SYSTEM. [Ch. IX. already stated that, during that vast period, a large proportion of all the lands in the northern hemisphere were raised above the level of the sea. ' The modifications in the system of which man is the instru- mentj do not, in all probability, constitute so great a deviation from analogy as we usually imagine ; we often, for example, form an exaggerated estimate of the extent of the power dis- played by man in extirpating some of the inferior animals, and causing others to multiply ; a power which is circumscribed within certain limits, and which, in all likelihood, is by no means exclusively exerted by our species. The growth of human po- pulation cannot take place without diminishing the numbers, or causing the entire destruction of many animals. The larger carnivorous species give way before us, but other quadrupeds of smaller size, and innumerable birds, insects, and plants, which are inimical to our interests, increase in spite of us, some attacking our food, others our raiment and persons, and others interfering with our agricultural and horticultural labours. We force the ox and the horse to labour for our advantage, and we deprive the bee of his store ; but, on the other hand, we raise the rich harvest with the sweat of our brow, and behold it devoured by myriads of insects, and we are often as incapable of arresting their depredations as of staying the shock of an earthquake, or the course of a stream of burning lava. The changes caused by other species, as they gradually diffuse themselves over the globe, are inferior probably in magnitude, but are yet extremely analogous to those which we occasion. The lion, for example, and the migratory locust, must neces- sarily, when they first made their way into districts now occu- pied by them, have committed immense havoc amongst the animals and plants which became their prey. They may have caused many species to diminish, perhaps wholly to disappear; but they must also have enabled some others greatly to augment in number, by removing the natural enemies by which they had been previously kept down. It is probable from these, and many other considerations, Ch. IX.] RECENT ORIGIN OF MAN. 187 that as we enlarge our knowledge of the system, we shall be- come more and more convinced, that the alterations caused by the interference of man deviate far less from the analogy of those effected by other animals than we usually suppose. We are often misled, when we institute such comparisons, by our knowledge of the wide distinction between the instincts of animals and the reasoning power of man ; and we are apt has- tily to infer, that the effects of a rational and an irrational species, considered merely as physical agents, will differ almost as much as the faculties by which their actions are directed. A great philosopher has observed, that we can only command nature by obeying her laws ; and this principle is true even in regard to the astonishing changes which are superinduced in the qualities of certain animals and plants by domestication and garden culture. We can only effect such surprising alter- ations by assisting the development of certain instincts, or by availing ourselves of that mysterious law of their organization,, by which individual peculiarities are transmissible from one generation to another. We are not, however, contending that a real departure from the antecedent course of physical events cannot be traced in the introduction of man. If that latitude of action which ena- bles the brutes. to accommodate themselves in some measure to accidental circumstances, could be imagined to have been at any former period so great, that the operations of instinct were as much diversified as are those of human reason, it might perhaps be contended, that the agency of man did not consti- tute an anomalous deviation from the previously established order of things. It might then have been said, that the earth's becoming at a particular period the residence of human beings, was an era in the moral, not in the physical world that our study and con- templation of the earth, and the laws which govern its animate productions, ought no more to be considered in the light of a disturbance or deviation from the system, than the discovery of the satellites of Jupiter should be regarded as a physical 188 UNIFORMITY OF THE SYSTEM. [Ch. IX. event in the history cf those heavenly bodies, however influ- ential they may have become from that time in advancing the progress of sound philosophy among men, and in augmenting human resources by aiding navigation and commerce. The distinctness, however, of the human, from all other species considered merely as an efficient cause in the physical world, is real, for we stand in a relation to contemporary species of animals and plant?, widely different from that which other irrational animals can ever be supposed to have held to each other. We modify their instincts, relative numbers, and geographical distribution, in a manner superior in degree, and in some respects very different in kind from that in which any other species can affect the rest. Besides, the progressive movement of each successive generation of men causes the human species to differ more from itself in power at two dis- tant periods, than any one species of the higher order of ani- mals differs from another. The establishment, therefore, by geological evidence of the first intervention of such a peculiar and unprecedented agency, long after other parts of the ani- mate and inanimate world existed, affords ground for con- cluding that the experience during thousands of ages of all the events which may happen on this globe would not enable a philosopher to speculate with confidence concerning future contingencies. If an intelligent being, therefore, after observing the order of events for an indefinite series of ages, had witnessed at last so wonderful an innovation as this, to what extent would his belief in the regularity of the system be weakened ? would he cease to assume that there was permanency in the laws of nature ? would he no longer be guided in his speculations by the strictest rules of induction? To this question we may reply, that had he previously presumed to dogmatize respect- ing the absolute uniformity of the order of nature, he would undoubtedly be checked by witnessing this new and unex- pected event, and would form a more just estimate of the limited range of his own knowledge, and the unbounded extent Ch. IX.] RECENT ORIGIN OF MAN. 189 of the scheme of the universe. But he would soon perceive that no one of the fixed and constant laws of the animate or inanimate world was subverted by human agency, and that the modifications produced were on the occurrence of new and extraordinary circumstances, and those not of a physical, but a moral nature. The deviation permitted, would also appear to be as slight as was consistent with the accomplishment of the new moral ends proposed, and to be in a great degree temporary in its nature, so that whenever the power of the new agent was withheld, even for a brief period, a relapse would take place to the ancient state of things \ the domesti- cated animal, for example, recovering in a few generations its wild instinct, and the garden-flower and fruit-tree reverting to the likeness of the parent stock. Now, if it would be reasonable to draw such inferences with respect to the future, we cannot but apply the same rules of induction to the past. It will scarcely be disputed that we have no right to anticipate any modifications in the results of existing causes in time to come, which are not conformable to analogy, unless they be produced by the progressive develop- ment of human power, or perhaps from some other new rela- tions between the moral and material worlds. In the same manner we must concede, that when we speculate on the vicis- situdes of the animate and inanimate creation in former ages, we have no ground for expecting any anomalous results, unless where man has interfered, or unless clear indications appear of some other moral source of temporary derangement. When we are unable to explain the monuments of past changes, it is always more probable that the difficulty arises from our igno- rance of all the existing agents, or all their possible effects in an indefinite lapse of time, than that some cause was formerly in operation which has ceased to act ; and if in any part of the globe the energy of a cause appears to have decreased, it is always probable, that the diminution of intensity in its action is merely local, and that its force is unimpaired, when the whole globe is considered. But should we ever establish 190 UNIFORMITY OF THE SYSTEM. [Ch. IX. by unequivocal proofs, that certain agents have, at particular periods of past time, been more potent instruments of change over the entire surface of the earth than they now are, it will be more consistent with philosophical caution to presume, that after an interval of quiescence they will recover their pristine vigour, than to regard them as worn out. The geologist who yields implicit assent to the truth of these principles, will deem it incumbent on him to examine with minute attention all the changes now in progress on the earth, and will regard every fact collected respecting the causes in diurnal action, as affording him a key to the interpretation of some mystery in the archives of remote ages. Our estimate, indeed, of the value of all geological evidence, and the interest derived from the investigation of the earth's history, must depend entirely on the degree of confidence which we feel in regard to the permanency of the laws of nature. Their immutable constancy alone can enable us to reason from ana- logy, by the strict rules of induction, respecting the events of former ages, or, by a comparison of the state of things at two distinct geological epochs, to arrive at the knowledge of general principles in the economy of our terrestrial system. The uniformity of the plan being once assumed, events which have occurred at the most distant periods in the animate and inanimate world will be acknowledged to throw light on each other, and the deficiency of our information respecting some of the most obscure parts of the present creation will be removed. For as by studying the external configuration of the existing land and its inhabitants, we may restore in imagi- nation the appearance of the ancient continents which have passed away, so may we obtain from the deposits of ancient seas and lakes an insight into the nature of the subaqueous processes now in operation, and of many forms of organic life, which though now existing, are veiled from our sight. Rocks, also produced by subterranean fire in former ages at great depths in the bowels of the earth, present us, when upraised by gradual movements, and exposed to the light of heaven, Ch. IX.J RECENT ORIGIN OF MAN. 191 with an image of those changes which the deep-seated volcano may now occasion in the nether regions. Thus, although we are mere sojourners on the surface of the planet, chained to a mere point in space, enduring but for a moment of time, the human mind is not only enabled to number worlds beyond the unassisted ken of mortal eye, but to trace the events of indefinite ages before the creation of our race, and is not even withheld from penetrating into the dark secrets of the ocean, or the interior of the solid globe ; free, like the spirit which the poet described as animating the universe, ire per omnes Terrasque tractusque marls, coeluinque profundum. CHAPTER X. Division of the subject into changes of the organic and inorganic world Inor- ganic causes of change divided into the aqueous and igneous Aqueous causes Destroying and transporting power of running water Sinuosities of rivers Two streams when united do not occupy a bed of double surface Heavy matter removed by torrents and floods Recent inundations in Scotland Effects of ice in removing stones Erosion of chasms through hard rocks Excavations in the lavas of Etna by Sicilian rivers Gorge of the Simeto Gradual recession of the cataracts of Niagara Speculations as to the time required for their reaching Lake Erie. CHANGES OF THE INORGANIC WORLD AQUEOUS CAUSES. Division of the subject. WE defined geology to be the science which investigates the former changes that have taken place in the organic, as well as in the inorganic kingdoms of nature ; and we now proceed to inquire what changes are now in pro- gress in both these departments. Vicissitudes in the inorganic world are most apparent ; and as on them all fluctuations in the animate creation must in a great measure depend, they may claim our first consideration. We may divide the great agents of change in the inorganic world into two principal classes, the aqueous and the igneous. To the former belong Rivers, Tor- rents, Springs, Currents, and Tides; to the latter, Volcanos and Earthquakes. Both these classes are instruments of decay as well as of reproduction ; but they may be also regarded as antagonist forces. The aqueous agents are incessantly labour- ing to reduce the inequalities of the earth's surface to a level, while the igneous, on the other hand, are equally active in restoring the unevenness of the external crust, partly by heaping up new matter in certain localities, and partly by depressing one portion, and forcing out another of the earth's envelope. It is difficult, in a scientific arrangement, to give an accu- Ch. X.] ACf ION OF RUNNING WATER* 193 rate view of the combined effects of so many forces in simul- taneous operation ; because, when we consider them sepa- rately, we cannot easily estimate either the extent of their efficacy, or the kind of results which they produce. We are in danger, therefore, when we attempt to examine the influence exerted singly by each, of overlooking the modifications which they produce on one another ; and these are so complicated, that sometimes the igneous and aqueous forces co-operate to produce a joint effect, to which neither of them unaided by the other could give rise, as when repeated earthquakes unite with running water to widen a valley. Sometimes the organic combine with the inorganic causes ; as when a reef, composed of shells and corals, protects one line of coast from the destroy- ing power of tides or currents, and turns them against some other point j or when drift timber, floated into a lake, fills a hollow to which the stream would not have had sufficient velo- city to convey earthy sediment. It is necessary, however, to divide our observations on these various causes, and to classify them systematically, endeavour- ing as much as possible to keep in view that the effects in nature are mixed, and not simple, as they may appear in an artificial arrangement. In treating, first, of the aqueous causes, we may consider them under two divisions: first, those which are connected with the circulation of water from the land to the sea, under which are included all the phenomena of rivers and springs ; secondly, those which arise from the movements of water in lakes, seas, and the ocean, wherein are comprised the phenomena of tides and currents. In turning our first attention to the former division, we find that the effects of rivers may be subdivided into those of a destroying and those of a renovating nature. In the former are included the erosion of rocks and the trans- portation of matter to lower levels; in the latter, the formation of sand-bars and deltas, the shallowing of seas, &c. Action of running water. We shall begin, then, by describ- ing the destroying and transporting power of running water, as VOL. I. O 194 ACTION OF RUNNING WATER. [Ch. X. exhibited by torrents and rivers. It is well known that the lands elevated above the sea attract in proportion to their volume and density a larger quantity of that aqueous vapour which the heated atmosphere continually absorbs from the surface of lakes and seas. By these means,, the higher regions become perpetual reservoirs of water, which descend and irrigate the lower valleys and plains. In consequence of this provision, almost all the water is first carried to the highest regions, and is then made to descend by steep declivities towards the sea ; so that it acquires superior velocity, and removes a greater quantity of soil than it would do if the rain had been distributed over the low plains and high mountains equally in proportion to their relative areas. Almost all the water is also made by these means to pass over the greatest distances which each region affords, before it can regain the sea. The rocks in the higher regions are particularly exposed to atmospheric influences, to frost, rain, and vapour, and to great annual alternations of moisture and desiccation* -of cold and heat. Its destroying and transporting power. Among the most powerful agents of decay may be mentioned the mechanical action of water, which possesses the remarkable property of expanding during congelation. When water has pene- trated into crevices and cavities, it rends open, on freezing, the most solid rocks with the force of a lever, and for this reason, although in cold climates the comparative quantity of rain which falls is very inferior, and although it descends more gradually than in tropical regions, yet the severity of frost, and the greater inequalities of temperature, compensate for this diminished power of degradation, and cause it to proceed with equal, if not greater rapidity than in low latitudes. The solvent power of water also is very great, and acts particularly on the calcareous and alkaline elements of stone, especially when it holds car- bonic acid in solution, which is abundantly supplied to almost every large river by springs, and is collected by rain from the atmosphere 1 . The oxygen of the atmosphere is also gradually absorbed by all animal and vegetable productions, and by Ch.X.] SINUOSITY OF RIVERS. 195 almost all mineral masses exposed to the open air. It gra- dually destroys the equilibrium of the elements of rocks, and tends to reduce into powder, and to render fit for soils, even the hardest aggregates belonging to our globe *. And as it is well known that almost everything effected by rapid com- bustion may also be effected gradually by the slow absorption of oxygen, the surface of the hardest rocks exposed to the air may be said to be slowly burning away. When earthy matter has once been intermixed with running water, a new mechanical power is obtained by the attrition of sand and pebbles, borne along with violence by a stream. Running water charged with foreign ingredients being thrown against a rock, excavates it by mechanical force, sapping and undermining till the superincumbent portion is at length preci- pitated into the stream. The obstruction causes a temporary increase of the water, which then sweeps down the barrier. By a repetition of these land-slips, the ravine is widened into a small, narrow valley, in which sinuosities are caused by the deflexion of the stream first to one side and then to the other. The unequal hardness of the materials through which the channel is eroded, tends also to give new directions to the lateral force of ex- cavation. When by these, or by accidental shif tings of the alluvial matter in the channel, and numerous other causes, the current is made to cross its general line of descent, it eats out a curve in the opposite bank, or the side of the hill bounding the valley, from which curve it is turned back again at an equal angle, and recrossing the line of descent, it gradually hollows out another curve lower down, in the opposite bank, till the whole sides of the valley, or river-bed, present a succession of salient and retiring angles. Sinuosities of rivers. Among the causes of deviation from a straight course by which torrents and rivers tend to widen the valleys through which they flow, may be mentioned the confluence of lateral torrents, swollen irregularly at different seasons in mountainous regions by partial storms, and discharg- * Sir H. Davy, Consolations in Travel, p. 271. 02 196 StNUOSITY OF RIVERS. [CH. X. ing at different times unequal quantities of debris into the main channel. When the tortuous flexures of a river are extremely great, the aberration from the direct line of descent is often restored by the river cutting through the isthmus which separates two neighbouring curves. Thus, in the annexed diagram, the No. 2, extreme sinuosity of the river has caused it to return for a brief space in a contrary direction to its main course, so that a peninsula is formed, and the isthmus (at a) is consumed on both sides by currents flowing in opposite directions. In this case an island is soon formed, on either side of which a portion of the stream usually remains *. These windings occur not only in the channels of rivers flowing through flat alluvial plains, but large valleys also are excavated to a great depth through solid rocks in this serpentine form. In the valley of the Moselle, between Berncastle and Roarn, which is sunk to a depth of from six to eight hundred feet through an elevated platform of transition rocks, the curves are so consi- derable that the river returns, after a course of seventeen miles in one instance, and nearly as much in two others, to within a distance of a few hundred yards of the spot it passed before f . The valley of the Meuse, near Givet, and many others in different countries, offer similar windings. Mr. Scrope has remarked, that these tortuous flexures are decisively opposed to the hypothesis, that any violent and transient rush of water suddenly swept out such valleys ; for great floods would pro- duce straight channels in the direction of the current, not * See a Paper on the Excavation of Valleys, &c., by G. Puiilett Scrope, Esq., Proceedings of Gcol. Soc., No, 14, 1830. f Ibid. Ch. X.] SINUOSITY OF RIVERS. 197 sinuous excavations, wherein rivers flow back again in an oppo- site direction to their general line of descent. We must not, however, conclude that the valley of the Meuse was formed simply by river action, for we believe it to have been due in great part to subterranean movements, and the agency of marine currents. Certain it is, that the waters of the sea once filled a great part of this valley, for at St. Mihiel, south of Verdun, about fifteen leagues from Givet, in a tract elevated perhaps one thousand feet above the level of the sea, M. Des- hayes discovered three lines of perforations of marine shells, of the genus saxicava, on the boundary cliffs ; and, at a corre- sponding level, the same lines are traceable round two insulated rocks in the middle of the valley. The rock consists of white marble of the Jura limestone formation, and casts of the boring shells still remain in the cavities. But our present purpose relates to the force of aqueous erosion, and the transportation of materials by running water, considered separately, and not to the question so much contro- verted respecting the formation of valleys in general. This sub- ject cannot be fully discussed without referring to all the powers to which the inequalities of the earth's surface, and the very ex- istence of land above the level of the sea, are due. Nor even when we have described the influence of all the chemical and me- chanical agents which operate at one period in effecting changes in the external form of the land, shall we be enabled to present the reader with a comprehensive theory of the origin of the pre- sent valleys. It will be necessary to consider the complicated effects of all these causes at distinct geological epochs, and to inquire how particular regions, after having remained for ages in a state of comparative tranquillity, and under the influence of a certain state of the atmosphere, may be subsequently remodelled by another series of subterranean movements, how the new direction, volume, and velocity acquired by rivers and torrents may modify the former surface, what effects an im- portant difference in the mean temperature of the climate, or the greater intensity of heat and cold at different seasons, may 198 TRANSPORTING POWER [Ch. X. produce, what pre-existing valleys, under a new configura- tion of the land, may cease to give passage to large bodies of water, or may become entirely dried up, how far the relative levels of certain districts in the more modern period may become precisely the reverse of those which prevailed at the more ancient era. When these and other essential elements of the problem are all duly appreciated, the reader will not be sur- prised to learn, that amongst geologists who have neglected them there has prevailed a great contrariety of opinion on these topics. Some writers of distinguished talent have gone so far as to contend, that the formation of the greater number of existing valleys was simply due to the agency of one cause, and that it was consummated in a brief period of time. But without discussing the merits of the general question, we may observe that we agree with the author before cited, that the sinuosity of deep valleys is one among many proofs that they have been shaped out progressively, and not by the simulta- neous action of one or many causes ; and when we consider other agents of change, we shall have opportunities of pointing out a multitude of striking facts in confirmation of the gradual nature of the process to which the inequalities of hill and valley owe their origin. Transporting power of water. In regard to the transport- ing power of water, we are often surprised at the facility where- with streams of a small size, and which descend a slight decli- vity, bear along coarse sand and gravel; for we usually estimate the weight of rocks in air, and do not reflect sufficiently on their comparative buoyancy when submerged in a denser fluid. The specific gravity of many rocks is not more than twice that of water, and very rarely more than thrice, so that almost all the fragments propelled by a stream have lost a third, and many of them half of what we usually term their weight. It has been proved by experiment, in contradiction to the theories of the early writers on hydrostatics, to be a universal law, regulating the motion of running water, that the velocity at the bottom of the stream is everywhere less than in any part Ch. X.] OF RUNNING WATER. 199 above it, and is greatest at the surface. Also that the super- ficial particles in the middle of the stream move swifter than those at the sides. This retardation of the lowest and lateral currents is produced by friction, and when the velocity is suf- ficiently great, the soil composing the sides and bottom gives way. A velocity of three inches per second is ascertained to be sufficient to tear up fine clay, six inches per second, fine sand, twelve inches per second, fine gravel, and three feet per second, stones of the size of an egg *. When this mechanical power of running water is considered, we are prepared for the transportation of large quantities of gravel, sand, and mud, by the torrents and rivers which de- scend with great velocity from the mountainous regions. But a question naturally arises, how the more tranquil rivers of the valleys and plains, flowing on comparatively level ground, can remove the prodigious burden which is discharged into them by their numerous tributaries, and by what means they are enabled to convey the whole mass to the sea. If they had not this power, their channels would be annually choked up, and the lower valleys and districts adjoining mountain-chains would be continually strewed over with fragments of rock and sterile sand. But this evil is prevented by a general law regulating the conduct of running water that two equal streams do not occupy a bed of double surface. In proportion, therefore, as the whole fluid mass increases, the space which it occupies decreases relatively to the volume of water; and hence there is a smaller proportion of the whole retarded by friction against the bottom and sides of the channel. The portion thus unim- peded moves with great velocity, so that the main current is often accelerated in the lower country, notwithstanding that the slope of the channel is lessened. It not unfrequently happens, as we shall afterwards demon- strate by examples, that two large rivers, after their junction, have only the surface which one of them had previously; and even in some cases their united waters are confined in a nar- * Encycl. Brit. art. Rivers. 200 TRANSPORTING POWER [Ch. X. rower bed than each of them filled before. By this beautiful adjustment, the water which drains the interior country is made continually to occupy less room as it approaches the sea ; and thus the most valuable part of our continents, the rich deltas, and great alluvial plains, are prevented from being con- stantly under water *. Floods in Scotland, 1829. Many remarkable illustrations of the power of running water in moving stones and heavy materials were afforded by the storm and flood which oc- curred on the 3rd and 4th of August, 1829, in Aberdeenshire and other counties in Scotland. The elements during this storm assumed all the characters which mark the tropical hur- ricanes ; the wind blowing in sudden gusts and whirlwinds, the lightning and thunder being such as is rarely witnessed in that climate, and heavy rain falling without intermission. The floods extended almost simultaneously, and in equal violence, over that part of the north-east of Scotland which would be cut off by two lines drawn from the head of Lochrannoch, one towards Inverness and another to Stonehaven. The united line of the rivers which were flooded could not be less than from five to six hundred miles in length, and the whole of their courses were marked by the destruction of bridges, roads, crops, and buildings. Sir T. D. Lauder has recorded the destruction of thirty-eight bridges, and the entire obliteration of a great number of farms and hamlets. On the Nairn, a fragment of sandstone rock, fourteen feet long by three feet wide and one foot thick, was carried above two hundred yards down the river. Some new ravines were formed on the sides of mountains where no streams had previously flowed, and ancient river-channels, which had never been filled from time immemorial, gave passage to a copious flood *. The bridge over the Dee at Ballatu consisted of five arches, having upon the whole a water-way of two hundred and sixty feet. The bed of the river, on which the piers rested, was * See article Rivers, Encyc. Brit. t Sir T. D. Lauder's Account of the Great Floods in Morayshirc, Aug. 1829, Ch. X.] OF RUNNING WATER. 201 composed of rolled pieces of granite and gneiss. The bridge was built of granite, and had stood uninjured for twenty years, but the different parts were swept away in suc- cession by the flood, and the whole mass of masonry disap- peared in the bed of the river *. ' The river Don/ observes Mr. Farquharson, in his account of the inundations, * has upon my own premises forced a mass of four or five hundred tons of stones, many of them two or three hundred pounds weight, up an inclined plane, rising six feet in eight or ten yards, and left them in a rectangular heap, about three feet deep, on a flat ground ; the heap ends abruptly at its lower extremity f.' The power even of a small rivulet, when swoln by rain, in removing heavy bodies, was lately exemplified in the College, a small stream which flows at a moderate declivity from the eastern water-shed of the Cheviot -Hills. Several thousand tons weight of gravel and sand were transported to the plain of the Till, and a bridge then in progress of building was carried away, some of the arch-stones of which, weighing from half to three-quarters of a ton each, were propelled two miles down the rivulet. On the same occasion the current tore away from the abutment of a mill-dam a large block of greenstone-por- phyry, weighing nearly two tons, and transported it to the distance of a quarter of a mile. Instances are related as occur- ring repeatedly, in which from one to three thousand tons of gravel are in like manner removed to great distances in one day I. In the cases above adverted to, the waters of the river and torrent were dammed back by the bridges, which acted as par- tial barriers, and illustrate the irresistible force of a current when obstructed. Bridges are also liable to be destroyed by the tendency of rivers to shift their course, whereby the pier, or the rock on which the foundation stands, is undermined. * From the account given by the Rev. James Farquharson, in the Quarterly Journ. of Sci., &c., No. xii., New Series, p. 328. f Ibid., p. 331. J See a paper by Mr. Culley, F.G.S. ? Proceedings of Geol. Soc. No. xii. ; 1829. 202 TRANSPORTING POWER OF RUNNING WATER. [Ch. X. When we consider how insignificant are the volume and velocity of the rivers and streams in our island, when compared to those of the Alps and other lofty chains, and how, during the various changes which the levels of different districts have undergone, the various contingencies which give rise to floods must in the lapse of ages be multiplied, we may easily conceive that the quantity of loose superficial matter distributed over Europe must be very considerable. That the position also of a great portion of these travelled materials should now appear most irregular, and should often bear no relation to the exist- ing water-drainage of the country, is a necessary consequence, as we shall afterwards see, of the combined operations of run- ning water and subterranean movements. Effects of ice in removing stones, In mountainous regions and high northern latitudes, the moving of heavy stones by water is greatly assisted by the ice which adheres to them, and which, forming together with the rock a mass of less specific gravity *, is readily borne along. The glaciers also of alpine regions, formed of consolidated snow, bear down upon their surface a prodigious burden of rock and sand mixed with ice. These materials are generally arranged in long ridges, which, sometimes, in the Alps, are thirty or forty feet high, running parallel to the borders of the glacier, like so many lines of intrenchment. These mounds of debris are sometimes three or more deep, and have generally been brought in by lateral glaciers : the whole accumulation is slowly conveyed to the lower valleys, where, on the melting of the glacier, it is swept away by rivers f. The rapidity with which even the smallest streams hollow out deep channels in soft and destructible soils is remarkably exemplified in volcanic countries, where the sand and half consolidated tuffs oppose but a slight resistance to the torrents which descend the mountain-side. After the heavy rains which followed the eruption of Vesuvius in 1822, the water * Silliman's Journal, No. xxx. p. 303. f Saussure, Voyage dans les Alpes, tome i. |Ch. X.] EROSION OF RAVINES. 203 flowing from the Atrio del Cavallo, cut in three days a new chasm through strata of tuff and volcanic ejected matter to the depth of twenty-five feet. The old mule-road was seen in 1828,, intersected by this new ravine. But such facts are tri- fling when compared to the great gorges which are excavated in somewhat similar materials in the great plateau of Mexico, where an ancient system of valleys, originally worn out of granite and secondary rocks, has been subsequently filled with strata of tuff, pumice, lava, and trachytic conglomerate, to the thickness of several thousand feet. The rivers and torrents annually swoln by tropical rains, are now actively employed in removing these more recent deposits, and in re-excavating the ancient water-courses *. Power of running water to excavate hard rocks. The gra- dual erosion of deep chasms through some of the hardest rocks, by the constant passage of running water charged with foreign matter, is another phenomenon of which striking examples may be adduced. Some of the clearest illustrations of this excavating power are presented by many valleys in Central France, where the channels of rivers have been barred up by solid currents of lava, through which the streams have re- excavated a passage to the depth of from twenty to seventy feet and upwards, and often of great width. In these cases there are decisive proofs that neither the sea nor any denuding wave, or extraordinary body of water, have passed over the spot since the melted lava was consolidated. Every hypothe- sis of the intervention of sudden and violent agency is entirely excluded, because the cones of loose scoriae, out of which the lavas flowed, are oftentimes at no great elevation above the rivers, and have remained undisturbed during the whole period which has been sufficient for the hollowing out of such enor- mous ravines. But we shall reserve a more detailed account of the volcanic district of Central France for another part of this work, and at present confine ourselves to examples * I am indebted to Captain Vetch for this information, whose researches in Mexico will, it is hoped, be soon communicated to the scientific world. 204 AQUEOUS EROSION OF LAVAS. [Ch. X. derived from events which have happened since the time of history. Some lavas of Etna, produced by eruptions of which the date is known, have flowed across two of the principal rivers in Sicily ; and in both cases the streams, dispossessed of their ancient beds, have opened for themselves new channels. An eruption from Mount Mojo, an insulated cone at the northern base of Etna, sent forth,, in the year 396, B.C., in the reign of Dionysius I., a great lava-stream, which crossed the river Cal- tabianca in two places. The lowermost point of obstruction is seen on the eastern side of Etna, on the high road from Giardini to Catania, where one pier of the bridge on either bank is based upon a remnant of the solid Java, which has been breached by the river to the depth of fourteen feet. But the Caltabianca, although it has been at work for more than two and twenty centuries, has not worn through the igneous rock so as to lay open the gravel of its ancient bed. The de- clivity, however, of the alluvial plain is very slight ; and as the extent of excavation in a given time depends on the volume and velocity of the stream, and the destructibility of the rock, we must carefully ascertain all these circumstances before we attempt to deduce from such examples a measure of the force of running water in a given period *. Recent excavation by the Simeto. The power of running water to hollow out compact rock is exhibited, on a larger scale at the western base of Etna, where a great current of lava (A A, diagram 3), descending from near the summit of the great volcano, has flowed to the distance of five or six miles, and then reached the alluvial plain of the Simeto, the largest of the Sicilian rivers which skirts the base of Etna, and falls into the sea a few miles south of Catania. The lava entered the river about three miles above the town of Aderno, * I omitted to visit the higher point near the village of Mojo, 'where the Calta- bianca has cut through the lava. Some future traveller would probably derive much instruction from inspecting that spot ; which is laid down in Gemmellaro's Quadro Istorico, &c, dell' Etna, 1824. Ch. X.] LAVA EXCAVATED HY THE SIMETO. 205 and not only occupied its channel for some distance, but, cross- No. 3. Recent excavation of lava at the foot of Etna by the river Simeto. ing to the opposite side of the valley, accumulated there in a rocky mass. Gemmellaro gives the year 1603 as the date of the eruption *. The appearance of the current clearly proves that it is one of the most modern of those of Etna, for it has not been covered or crossed by subsequent streams or ejections, and the olives on its surface are all of small size, yet older than the natural wood on the same lava. In the course, therefore, of about two centuries the Simeto has eroded a passage from fifty to several hundred feet wide, and in some parts from forty to fifty feet deep. The portion of lava cut through is in no part porous or scoriaceous, but consists of a compact homogeneous mass of hard blue rock, somewhat lighter than ordinary basalt, con- taining crystals of olivine and glassy felspar. The general declivity of this part of the bed of the Simeto is not consider- able, but, in consequence of the unequal waste of the lava, two waterfalls occur at Passo Manzanelli, each about six feet in height. Here the chasm (B, diagram No. 3.) is about forty feet deep, and only fifty broad. The sand and pebbles in the river bed consist chiefly of a brown quartzose sandstone, derived from the upper country ; but the matter derived from the volcanic rock itself must have greatly assisted the attrition. This river, like the Caltabianca, * Quadro Istorico dell' Etna, 1824. Some doubts are entertained as to the exact date [of this current by others, but all agree that it is not one of Ihe older streams even of the historical era. 206 FALLS OF NIAGARA. [Ch. X. has not yet cut down to the ancient bed of which it was dispos- sessed, and of which we have indicated the probable position in the annexed diagram (c, No. 3.) On entering the narrow ravine where the water foams down the two cataracts, we are entirely shut out from all view of the surrounding country; and a geologist who is accustomed to associate the characteristic features of the landscape with the relative age of certain rocks, can scarcely dissuade himself from the belief that he is contemplating a scene in some rocky gorge of a primary district. The external forms of the hard blue lava are as massive as any of the most ancient trap-rocks of Scotland. The solid surface is in some parts smoothed and almost polished by attrition, and covered in others with a white lichen, which imparts to it an air of extreme antiquity, so as greatly to heighten the delusion. But the moment we re- ascend the cliff, the spell is broken ; for we scarcely recede a few paces, before the ravine and river disappear, and we stand on the black and rugged surface of a vast current of lava, which seems unbroken, and which we can trace up nearly to the distant summit of that majestic cone which Pindar called ' the pillar of heaven,' and which still continues to send forth a fleecy wreath of vapour, reminding us that its fires are not extinct, and that it may again give out a rocky stream, wherein other scenes like that now described may present themselves to future observers. Falls of Niagara. The falls of Niagara afford a magnificent example of the progressive excavation of a deep valley in solid rock. That river flows from Lake Erie to Lake Ontario, the former lake being three hundred and thirty feet above the lat- ter, and the distance between them being thirty-two miles. On flowing out of the upper lake, the river is almost on a level with its banks ; so that if it should rise perpendicularly eight or ten feet, it would lay under water the adjacent flat country of Upper Canada on the West, and of the State of New York on the East*. The river, where it issues, is about three-quarters of * Captain Hall's Travels in North America, vol. i., p. 179. Ch. X.] FALLS OF NIAGABA. 207 a mile in width. Before reaching the falls, it is propelled with great rapidity, being a mile broad, about twenty-five feet deep, and having a descent of fifty feet in half a mile. An island at the very verge of the cataract divides it into two sheets of water ; one of these, called the Horse-shoe Fall, is six hundred yards wide, and one hundred and fifty-eight feet perpendicular; the other, called the American Falls, is about two hundred yards in width, and one hundred and sixty-four feet in height. The breadth of the island is about five hundred yards. This great sheet of water is precipitated over a ledge of hard limestone, in horizontal strata, below which is a somewhat greater thickness of soft shale, which decays and crumbles away more rapidly, so that the calcareous rock forms an overhanging mass, projecting forty feet or more above the hollow space below. The blasts of wind, charged with spray, which rise out of the pool into which this enormous cascade is projected, strike against the shale beds, so that their disintegration is constant ; and the superincumbent limestone, being left without a foun- dation, falls from time to time in rocky masses. When these enormous fragments descend, a shock is felt at some distance, accompanied by a noise like a distant clap of thunder. After the river has passed over the falls, its character, observes Captain Hall, is immediately and completely changed. It then runs furiously along the bottom of a deep wall-sided valley, or huge trench, which has been cut into the horizontal strata by the continued action of the stream during the lapse of ages. The cliffs on both sides are in most places perpendicular, and the ravine is only perceived on approaching the edge of the precipice *. The waters which expand at the falls, where they are divided by the island, are contracted again, after their union, into a stream not more than one hundred and sixty yards broad. In the narrow channel, immediately below this immense rush of water, a boat can pass across the stream with ease. The pool, it is said, into which the cataract is precipitated, being one hun- * Captaia Hall's Travels in North America, vol. i. pp. 195, 196, 216. 208 FALLS OF NIAGARA. [Ch. X. dred and seventy feet deep, the descending water sinks down and forms an under-current, while a superficial eddy carries the upper stratum back towards the main fall *. This is not improbable; and we must also suppose, that the confluence of the two streams, which meet at a considerable angle, tends mutually to neutralize their forces. The bed of the river below the falls is strewed over with huge fragments which have been hurled down into the abyss. By the continued destruction of the rocks, the falls have, within the last forty years, receded nearly fifty yards, or, in other words, the ravine has been prolonged to that extent. Through this deep chasm the Niagara flows for about seven miles ; and then the table-land, which is almost on a level with Lake Erie, sud- denly sinks down at a town called Queenstown, and the river emerges from the ravine into a plain which continues to the shores of Lake Ontario f. Recession of the Falls. There seems good foundation for the general opinion, that the falls were once at Queenstown, and that they have gradually retrograded from that place to their present position, about seven miles distant. If the ratio of recession had never exceeded fifty yards in forty years, it must have required nearly ten thousand years for the excava- tion of the whole ravine ; but no probable conjecture can be offered as to the quantity of time consumed in such an opera- tion, because the retrograde movement may have been much more rapid when the whole current was confined within a space not exceeding a fourth or fifth of that which the falls now oc- cupy. Should the erosive action not be accelerated in future, it will require upwards of thirty thousand years for the falls to reach Lake Erie (twenty-five miles distant), to which they seem destined to arrive in the course of time, unless some earth- quake changes the relative levels of the district. * See Mr. Bakewell, jun., on the Falls of Niagara. London's Magazine, No. xii. March, 1830. f The Memoir of Mr. Ba"1cewell, jun., above referred to, contains two very illus- trative sketches of the physical geograp v >y of the country between Lakes Erie and Ontario, including the Falls. Ch. X.] FALLS OF NIAGARA. 209 The table-land,, extending from Lake Erie, consists uniformly of the same geological formations as are now exposed to view at the falls. The upper stratum is an ancient alluvial sand, varying in thickness from ten to one hundred and forty feet below which is a bed of hard limestone, about ninety feet in thickness, stretching nearly in a horizontal direction over the whole country, and forming the bed of the river above the falls, as do the inferior shales below. The lower shale is nearly of the same thickness as the limestone. Should Lake Erie re- main in its present state until the period when the ravine recedes to its shores, the sudden escape of that great body of water would cause a tremendous deluge ; for the ravine would be much more than sufficient to drain the whole lake, of which the average depth was found, during the late survey, to be only ten or twelve fathoms. But, in consequence of its shallowness, Lake Erie is fast filling up with sediment, and the annual growth of the deltas of many rivers and torrents which flow into it is remarkable. Long Point, for example, near the influx of Big Creek River, was observed, during the late survey, to advance three miles in as many years. A question therefore arises, whether Lake Erie may not be converted into dry land before the Falls of Niagara recede so far. In speculating on this contingency, we must not omit one important condition of the problem. As the surface of the lake is contracted in size, the loss of water by evaporation will diminish ; . and unless the supply shall decrease in the same ratio (which seems scarcely probable), Niagara must augment continually in volume, and by this means its retrograde movement may hereafter be much accele- rated. VOL. I. CHAPTER XI. Action of running water, continued Course of the Po Desertion of its old chan- nel Artificial embankments of the Po, Adige, and other Italian rivers Basin of the Mississippi Its meanders Islands Shifting of its course Raft of the Atchafalaya Drift wood New-formed lakes in Louisiana Earthquakes in the valley of the Mississippi Floods caused by land-slips in the White moun- tains Bursting of a lake in Switzerland Devastations caused by the Anio at Tivoli. ACTION OF RUNNING WATER, continued. Course of the Po. The Po affords a grand example of the manner in which a great river bears down to the sea the matter poured into it by a multitude of tributaries descending from lofty chains of mountains. The changes gradually effected in the great plain of Northern Italy, since the time of the Roman republic, are very considerable. Extensive lakes and marshes have been gradually filled up, as those near Placentia, Parma, and Cremona, and many have been drained naturally by the deepening of the beds of rivers. Deserted river-courses are not unfrequent, as that of the Serio Morto, which formerly fell into the Adda, in Lombardy; and the Po itself has often deviated from its course. Subsequently to the year 1390, it deserted part of the territory of Cremona, and invaded that of Parma ; its old channel being still recognizable, and bearing the name of Po Morto. Bressello is one of the towns of which the site was formerly on the left of the Po, but which is now on the right bank. There is also an old channel of the Po in the territory of Parma, called Po Vecchio, which was abandoned in the twelfth century, when a great number of towns were destroyed. There are records of parish-churches, as those of Vicobellignano, Agojolo, and Martignana, having been pulled down and afterwards rebuilt at a greater distance from the de- vouring stream. In the fifteenth century the main branch Ch. XL] EMBANKMENTS OF PO AND ADIGE. 211 again resumed its deserted channel, and carried away a great island opposite Casalmaggiore. At the end of the same cen- tury it abandoned, a second time, the bed called ' Po Vecchio,' carrying away three streets of Casalmaggiore. The friars in the monastery de' Serviti took the alarm in 1471, demolished their buildings, and reconstructed them at Fontana, whither they had transported the materials. In like manner, the church of S. Rocco was demolished in 1511. In the seventeenth cen- tury also the Po shifted its course for a mile in the same dis- trict, causing great devastations*. Artificial embankments of Italian rivers. To check these and similar aberrations, a general system of embankment has been adopted ; and the Po, Adige, and almost all their tribu- taries, are now confined between high artificial banks. The in- creased velocity acquired by streams thus closed in, enables them to convey a much larger portion of foreign matter to the sea ; and, consequently, the deltas of the Po and Adige have gained far more rapidly on the Adriatic since the practice of embank- ment became almost universal. But although more sediment is borne to the sea, part of the sand and mud, which in the natural state of things would be spread out by annual inunda- tions over the plain, now subsides in the bottom of the river- channels, and their capacity being thereby diminished, it is necessary, in order to prevent inundations in the following spring, to extract matter from the bed, and to add it to the banks, of the river. Hence it has arisen that these streams now traverse the plain on the top of high mounds, like the waters of aqueducts, and the surface of the Po has become more elevated than the roofs of the houses of the city of Fer- rara y. The magnitude of these barriers is a subject of in- creasing expense and anxiety, it having sometimes of late years been found necessary to give an additional height of nearly one foot to the banks of the Adige and Po in a single season. * Dell' Antico Cor so de' Fiumi Po, Oglio, ed Adda dell' Giovanni Romani. Milan, 1828. f Prony, see Cuvier, Disc. Prelim., p. 146. P 2 212 BASIN OF THE MISSISSIPPI. [Ch. XI. The practice of embankment was adopted on some of the Italian rivers as early as the thirteenth century ; and Dante, writing in the beginning of the fourteenth, describes, in the seventh circle of hell, a rivulet of tears separated from a burn- ing sandy desert by embankments ' like those which, between Ghent and Bruges, were raised against the ocean, or those which the Paduans had erected along the Brenta to defend their villas on the melting of the Alpine snows.' Quale i Fiamminghi tra Guzzante e Bruggia, Temendo ii fiotto che in ver lor s' avveuta, Farino lo schermo, perche il mar si fuggia, E quale i Padovan lungo la Brenta, Per difender lor ville e lor castelli, Anzi che Chiarentana il caldo senta Inferno, Canto xv. Basin of the Mississippi. The hydrographical basin of the Mississippi displays, on the grandest scale, the action of run- ning water on the surface of a vast continent. This magnifi- cent river rises nearly in the forty-ninth parallel of north lati- tude, and flows to the Gulf of Mexico in the twenty-ninth a course, including its meanders, of nearly five thousand miles. It passes from a cold arctic climate, traverses the temperate regions, and discharges its waters into the sea in the region of the olive, the fig, and the sugar-cane*. No river affords a more striking illustration of the law before mentioned, that an augmentation of volume does not occasion a proportional in- crease of surface, nay, is even sometimes attended with a nar- rowing of the channel. The Mississippi is half a mile wide at its junction with the Missouri f , the latter being also of equal width ; yet the united waters have only, from their confluence to the mouth of the Ohio, a medial width of about three- quarters of a mile. The junction of the Ohio seems also to * Flint's Geography, vol. i. p. 21. t Flint says (vol. i. p. 140) that, where the Mississippi receives the Missouri, it is a mile and a half wide, but, according to Captain B. Hall, this is a great mis- take. Travels in the United States, vol. iii, p. 328. Ch. XL] CURVES OF THE MISSISSIPPI. 213 produce no increase, but rather a decrease of surface *. The St. Francis, White, Arkansas, and Red rivers, are also ab- sorbed by the main stream with scarcely any apparent increase of its width ; and, on arriving near the sea at New Orleans, it is somewhat less than half a mile wide. Its depth there is very variable, the greatest at high water being one hundred and sixty-eight feet. The mean rate at which the whole body of water flows is variously estimated. According to some, it does not exceed one mile an hour-J*. The alluvial plain of this great river is bounded on the east and west by great ranges of mountains stretching along their respective oceans. Below the junction of the Ohio, the plain is from thirty to fifty miles broad, and after that point it goes on increasing in width till the expanse is perhaps three times as great ! On the borders of this vast alluvial tract are perpen- dicular cliffs, or ' bluffs,' as they are called, composed of lime- stone and other rocks. For a great distance the Mississippi washes the eastern ' bluffs ;' and below the mouth of the Ohio, never once comes in contact with the western. The waters are thrown to the eastern side, because all the large tributary rivers enter from the west, and have filled that side of the great valley with a sloping mass of clay and sand. For this reason, the eastern bluffs are continually undermined, and the Mississippi is slowly but incessantly progressing eastward . Curves of the Mississippi. The river traverses the plain in a meandering course, describing immense and uniform curves. After sweeping round the half of a circle, it is precipitated from the point in a current diagonally across its own channel, to another curve of the same uniformity upon the opposite shore . These curves are so regular, that the boatmen and Indians calculate distances by them. Opposite to each of * Flint's Geography, vol. i.p. 142. f Hall's Travels in North America, vol. iii. p. 330, who cites Darby. J Geograph. Descrip. of the State of Louisiana, by W. Darby, Philadelphia, 1816, p. 102. Flint's Geog., vol. i. p. 152. 214 TRANSPORTATION OF MATTER [Ch. XI. them there is always a sand-bar, answering, in the convexity of its form, to the concavity of ' the bend/ as it is called *. The river, by continually wearing these curves deeper, returns, like many other streams before described, on its own tract, so that a vessel in some places, after sailing for twenty-five or thirty miles, is brought round again to within a mile of the place whence it started. When the waters approach so near to each other, it often happens at high floods that they burst through the small tongue of land ; and, having insulated a portion, rush through what is called the ' cut off' with great velocity. At one spot called the ' grand cut off, 1 vessels now pass from one point to another in half a mile to a distance which it formerly required a voyage of twenty miles to reachf. Waste of its banks. After the flood season, when the river subsides within its channel, it acts with destructive force upon the alluvial banks, softened and diluted by the recent overflow. Several acres at a time, thickly covered with wood, are pre- cipitated into the stream ; and the islands formed by the pro- cess before described lose large portions of their outer circum- ference. * Some years ago,' observes Captain Hall, ' when the Missis- sippi was regularly surveyed, all its islands were numbered, from the confluence of the Missouri to the sea ; but every sea- son makes such revolutions, not only in the number but in the magnitude and situation of these islands, that this enumeration is now almost obsolete. Sometimes large islands are entirely melted away at other places they have attached themselves to the main shore, or, which is the more correct statement, the interval has been filled up by myriads of logs cemented together by mud and rubbish J.' When the Mississippi and many of its great tributaries overflow their banks, the waters, being no longer borne down by the main current, and becoming impeded amongst the trees and bushes, deposit the sediment of mud and sand with which they are abundantly charged. Islands * Flint's Geog., vol. i. p. 152. f Ibid., p. 154. J Travels in North America, vol. iii. p. 361. Ch. XL] BY THE MISSISSIPPI. 215 arrest the progress of floating trees, and they become in this manner reunited to the land ; the rafts of trees, together with mud, constituting at length a solid mass. The coarser portion subsides first, and the most copious deposition is found near the banks where the soil is most sandy. Finer particles are found at the farthest distances from the river, where an impal- pable mixture is deposited, forming a stiff unctuous black soil. Hence the alluvions of these rivers are highest directly on the banks, and slope back like a natural ' glacis' towards the rocky cliffs bounding the great valley *. The Mississippi, therefore, by the continual shifting of its course, sweeps away, during a great portion of the year, considerable tracts of alluvium which were gradually accumulated by the overflow of former years, and the matter now left during the spring-floods will be at some future time removed. Raft of the Atchafalaya. One of the most interesting fea- tures in this basin is ' the raft.** The dimensions of this mass of timber were given by Darby in 1816, as ten miles in length, about two hundred and twenty yards wide, and eight feet deep, the whole of which had accumulated, in consequence of some obstruction, during about thirty-eight years, in an arm of the Mississippi called the Atchafalaya, which is supposed to have been at some past time a channel of the Red River, before it intermingled its waters with the main stream. This arm is in a direct line with the direction of the Mississippi, and it catches a large portion of the driftwood annually brought down. The mass of timber in the raft is continually increas- ing, and the whole rises and falls with the water. Although floating, it is covered with green bushes, like a tract of solid land, and its surface is enlivened in the autumn by a variety of beautiful flowers. Drift Wood. Notwithstanding the astonishing number of cubic feet of timber collected here in so short a time, greater deposits have been in progress at the extremity of the delta in the Bay of Mexico. Unfortunately for the navigation of the * Flint's Geography, vol. i. p. 151. 216 DRIFT WOOD OF THE MISSISSIPPI. [Ch. XI. Mississippi,' observes Captain Hall, ' some of the largest trunks, after being cast down from the position on which they grew, get their roots entangled with the bottom of the river, where they remain anchored, as it were, in the mud. The force of the current naturally gives their tops a tendency downwards, and by its flowing past, soon strips them of their leaves and branches. These fixtures, called snags or planters, are extremely dangerous to the steam-vessels proceeding up the stream, in which they lie like a lance in rest, concealed beneath the water, with their sharp ends pointed directly against the bow of vessels coming up. For the most part, these formidable snags remain so still, that they can be detected only by a slight ripple above them, not perceptible to inexpe- rienced eyes. Sometimes, however, they vibrate up and down, alternately showing their heads above the surface and bathing them beneath it V So imminent is the danger caused by these obstructions, that almost all the boats on the Mississippi are constructed on a particular plan, to guard against fatal accidents f. The prodigious quantity of wood annually drifted down by the Mississippi and its tributaries, is a subject of geological inte- rest, not merely as illustrating the manner in which abundance of vegetable matter becomes, in the ordinary course of Nature, imbedded in submarine and estuary deposits, but as attesting the constant destruction of soil and transportation of matter to lower levels by the tendency of rivers to shift their courses. Each of these trees must have required many years, some of them many centuries, to attain their full size ; the soil, there- fore, whereon they grew, after remaining undisturbed for long * Travels in North America, vol. iii. p. 362. t ' The boats are fitted,' says Captain Hall, ' with what is called a snag- chamber ; a partition, formed of stout planks, which is caulked, and made so effectually water-tight, that the foremost end of the vessel is cut off as entirely from the rest of the hold as if it belonged to another boat. If the steam-vessel happen to run against a snag, and that a hole is made in her bow, under the sur- face, this chamber merely fills with water.' Travels in North America, vol. iii. p. 363. Ch. XI.] DRIFT WOOD OF THE MISSISSIPPI. 217 periods, is ultimately torn up and swept away. Yet notwith- standing this incessant destruction of land and up-rooting of trees, the region which yields this never-failing supply of drift wood is densely clothed with noble forests, and is almost un- rivalled in its power of supporting animal and vegetable life. Innumerable herds of wild deer and bisons feed on the luxurious pastures of the plains. The jaguar, the wolf, and the fox, are amongst the beasts of prey. The waters teem with alligators and tortoises, and their surface is covered with millions of migratory water-fowl, which perform their annual voyage between the Canadian lakes and the shores of the Mexican gulf. The power of man begins to be sensibly felt, and the wilderness to be replaced by towns, orchards, and gardens. The gilded steam-boat, like a moving city, now stems the current with a steady pace now shoots rapidly down the descending stream through the solitudes of the forests and prairies. Already does the flourishing population of the great valley exceed that of the thirteen United States when first they declared their independence, and after a sanguinary struggle were severed from the parent country *. Such is the state of a continent where rocks and trees are hurried annually, by a thou- sand torrents, from the mountains to the plains, and where sand and finer matter are swept down by a vast current to the sea, together with the wreck of countless forests and the bones ' O of animals which perish in the inundations. When these mate- rials reach the Gulf, they do not render the waters unfit for aquatic animals ; but, on the contrary, the ocean here swarms with life, as it generally does where the influx of a great river furnishes a copious supply of organic and mineral matter. Yet many geologists, when they behold the spoils of the land heaped in successive strata, and blended confusedly with the remains of fishes, or interspersed with broken shells and corals, imagine that they are viewing the signs of a turbulent, instead of a tranquil and settled state of the planet. They read in such phenomena the proof of chaotic disorder, and * Flint's Geography, vol. i. 218 NEW LAKES IN LOUISIANA. [Ch. XI. reiterated catastrophes, instead of indications of a surface as habitable as the most delicious and fertile districts now tenanted by man. They are not content with disregarding the analogy of the present course of Nature, when they speculate on the revolutions of past times, but they often draw conclu- sions concerning the former state of things directly the reverse of those to which a fair induction from facts would infallibly lead them. Formation of lakes in Louisiana. There is another strik- ing feature in the basin of the Mississippi, illustrative of the changes now in progress, which we must not forget to mention the formation by natural causes of great lakes, and the drainage of others. These are especially frequent in the basin of the Red River in Louisiana, where the largest of them, called Bistineau, is more than thirty miles long, and has a medium depth of from fifteen to twenty feet. In the deepest parts are seen numerous cypress trees, of all sizes, now dead, and most of them with their tops broken by the wind, yet standing erect under water. This tree resists the action of air and water longer than any other, and, if not submerged throughout the whole year, will retain life for an extraordinary period *. Lake Bistineau, as well as Black Lake, Cado Lake, Spanish Lake, Natchitoches Lake, and many others, have been formed, according to Darby, by the gradual elevation of the bed of Red River, in which the alluvial accumulations have been so great as to raise its channel, and cause its waters, during the flood season, to flow up the mouths of many tribu- taries, and to convert parts of their courses into lakes. In the autumn, when the level of Red River is again depressed, the waters rush back again, and some lakes become grassy meadows, with streams meandering through themf. Thus, * Captains Clark and Lewis found a forest of pines standing erect under water in the body of the Columbia River in North America, which they supposed, from the appearance of the trees, to have been only submerged about twenty years. Vol. ii. p. 241. f- Darby's Louisiana, p. 33. Ch. XI.] EARTHQUAKES IN BASIN OF MISSISSIPPI. 219 there is a periodical flux and reflux between Red River and some of these basins, which are merely reservoirs, alter- nately emptied and filled like our tide estuaries with this dif- ference, that in the one case the land is submerged for several months continuously, and, in the other, twice in every twenty- four hours. It has happened, in several cases, that a bar has been thrown by Red River across some of the openings of these channels, and then the lakes become, like Bistineau, con- stant repositories of water. But even in these cases, their level is liable to annual elevation and depression, because the flood when at its height passes over the bar ; just as, where sand-hills close the entrance of an estuary on the Norfolk or Suffolk coast, the sea, during some high tide or storm, has often breached the barrier and inundated again the interior. Earthquakes in basin of Mississippi. The frequent fluc- tuations in the direction of river-courses, and the activity exerted by running water in various parts of the basin of the Mississippi, are partly, perhaps, to be ascribed to the co-operation of subterranean movements, which alter from time to time the relative levels of various parts of the surface. So late as the year 1812, the whole valley from the mouth of the Ohio to that of the St. Francis, including a front of three hundred miles, was convulsed to such a degree, as to create new islands in the river, and lakes in the alluvial plain, some of which were twenty miles in extent. We shall allude to this event when we treat of earthquakes, but may state here that they happened exactly at the same time as the fatal convulsions at Caraccas ; and the district shaken was nearly five degrees of latitude farther removed from the great centre of volcanic dis- turbance, than the basin of the Red River, to which we before alluded *. When countries are liable to be so extensively and perma- * Darby mentions beds of marine shells on the banks of Red River, which seem to indicate that Lower Louisiana is of recent formation : its elevation, per- haps, above the sea, may have been due to the same series of earthquakes which continues to agitate equatorial America. 220 FLOODS, BURSTING OF LAKES, ETC. [Ch. XI. nently affected by earthquakes, speculations concerning changes in their hydrographical features must not be made without regard to the igneous as well as the aqueous causes of change. It is scarcely necessary to observe, that the inequalities pro- duced even by one shock, might render the study of the allu- vial plain of the Mississippi, at some future period, most per- plexing to a geologist who should reason on the distribution of transported materials, without being aware that the configura- tion of the country had varied materially during the time when the excavating or removing power of the river was greatest. The region convulsed in 1812, of which New Madrid was the centre, exceeded in length the whole basin of the Thames, and the shocks were connected with active volcanos more distant from New Madrid than are the extinct craters of the Eyfel or of Auvergne from London. If, therefore, during the innume- rable eruptions which formerly broke forth in succession in the parts of Europe last alluded to, the basin of the principal river of our island was frequently agitated, and the relative levels of its several parts altered (an hypothesis in perfect accordance with modern analogy), the difficulties of some theorists might, perhaps, be removed; and they might no longer feel themselves under the necessity of resorting to catastrophes out of the ordi- nary course of Nature, when they endeavour to explain the alluvial phenomena of that district. FLOODS, BURSTING OF LAKES, &c. The power which running water may exert, in the lapse of ages, in widening and deepening a valley, does not so much de- pend on the volume and velocity of the stream usually flowing in it, as on the number and magnitude of the obstructions which have, at different periods, opposed its free passage. If a torrent, however small, be effectually dammed up, the size of the valley above the barrier, and its declivity below, will de- termine the violence of the debacle, and not the dimensions of the torrent. The most universal source of local deluges are land-slips, slides, or avalanches, as they are sometimes Ch. XL] FLOODS IN* NORTH AMERICA. 221 called, when great masses of rock and soil, or sometimes ice and snow, are precipitated into the bed of a river, either by the undermining of a cliff, by the loosening of a sub-stratum bv springs, by the shock of an earthquake, or other causes. Volumes might be filled were we to enumerate all the instances which are on record of these terrific catastrophes : we may therefore select a few examples of recent occurrence, the facts of which are well authenticated. Floods caused by land-slips, 1826. Two dry seasons in the White Mountains, in New Hampshire, were followed by heavy rains on the 28th August, 1826, when from the steep and lofty declivities which rise abruptly on both sides of the river Saco, innumerable rocks and stones, many of sufficient size to fill a common apartment, were detached, and in their descent swept down before them, in one pro- miscuous and frightful ruin, forests, shrubs, and the earth which sustained them. No tradition existed of any similar slides at former times, and the growth of the forest on the flanks of the hills clearly showed that for a long interval nothing similar had occurred. One of these moving masses was afterwards found to have slid three miles, with an average breadth of a quarter of a mile. The excavations commenced generally in a trench a few yards in depth and a few rods in width, and descended the mountains, widening and deep- ening till they became vast chasms. At the base of such hollow ravines was seen a wide and deep mass of ruins, con- sisting of transported earth, gravel, rocks, and trees. Forests of spruce-fir and hemlock were prostrated with as much ease as if they had been fields of grain ; for, where they disputed the ground, the torrent of mud and rock accumulated behind till it gathered sufficient force to burst the temporary barrier. The valleys of the Amonoosuck and Saco presented, for many miles, an uninterrupted scene of desolation, all the bridges being carried away, as well as those over their tributary streams. In some places, the road was excavated to the depth of from fifteen to twenty feet ; in others, it was covered with earth. 222 BURSTING OF A LAKE. [Ch. XI. rocks, and trees, to as great a height. The water flowed for many weeks after the flood, as densely charged with earth as it could be without being changed into mud, and marks were seen in various localities of its having risen on either side of the valley to more than twenty-five feet above its ordinary level. Many sheep and cattle were swept away, and the Willey family,, nine in number, who in alarm had deserted their house, were destroyed on the banks of the Saco ; seven of their mangled bodies were afterwards found near the river, buried beneath drift-wood and mountain-ruins *. It is almost super- fluous to point out to the reader that the lower alluvial plains are most exposed to such violent floods, and are at the same time best fitted for the sustenance of herbivorous animals. If, therefore, any organic remains are found amidst the superficial heaps of transported matter, resulting from those catastrophes, at whatever periods they may have happened, and whatever may have been the former configuration and relative levels of the country, we may expect the imbedded fossil relics to be principally referrible to this class of mammalia. But these catastrophes are insignificant, when compared to those which are occasioned by earthquakes, when the boundary hills, for miles in length, are thrown down into the hollow of a valley. We shall have an opportunity of alluding to inunda- tions of this kind when treating of earthquakes, and shall con- tent ourselves at present with selecting an example, of modern date, of a flood caused by the bursting of a lake ; the facts having been described, with more than usual accuracy, by sci- entific observers. Flood in the Valley ofBagnes, 1818. The valley of Bagnes is one of the largest of the lateral embranchments of the main valley of the Rhone, above the Lake of Geneva. Its upper portion was, in 1818, converted into a lake by the damming up of a narrow pass, in consequence of the fall of avalanches of snow and ice, precipitated from an elevated glacier into the bed of the river Dranse. In the winter season, during con- * Silliman's Journal of Science, vol. xv. No, 2, p. 216, Jan. 1829. Ch. XI.] IN THE VALLEY OF BAGNES. 223 tinued frost, scarcely any water flows in the bed of this river to preserve an open channel, so that the ice-barrier remained entire until the melting of the snows in spring, when a lake was formed above, about half a league in length, which finally attained a depth of about two hundred feet in parts, and a width of about seven hundred feet. To prevent or lessen the mischief apprehended from the sudden bursting of the barrier, an artificial gallery, seven hundred feet in length, was cut through the ice, before the waters had risen to a great height. When at length they accumulated and flowed through this tunnel, they dissolved the ice, and thus deepened their channel, until nearly half of the whole contents of the lake were slowly drained off. But, at length, on the approach of the hot season, the central portion of the remaining mass of ice gave way with a tremendous crash, and the residue of the lake was emptied in half an hour. In the course of its descent, the waters encoun- tered several narrow gorges, and at each of these they rose to a great height, and then burst with new violence into the next basin, sweeping along rocks, forests, houses, bridges, and culti- vated land. For the greater part of its course the flood re- sembled a moving mass of rock and mud, rather than of water. Some fragments of primary rock, of enormous magnitude, and which, from their dimensions, might be compared without exaggeration to houses, were torn out of a more ancient allu- vion, and borne down for a quarter of a mile. The velocity of the water, in the first part of its course, was thirty-three feet per second, which diminished to six feet before it reached the Lake of Geneva, where it arrived in six hours and a half, the distance being forty-five miles*. This flood left behind it, on the plains of Martigny, thou- sands of trees torn up by the roots, together with the ruins of buildings. Some of the houses in that town were filled with mud up to the second story. After expanding in the plain * See an account of the inundation of the Val de Bagnes, in 1818, in Ed. Phil. Journ.j vol. i., p. 187. Drawn up from the Memoir of M. Escher, with a sec- tion, &c. 224 FLOOD IN THE VALLEY OF BAGNES. [Ch. XI. of Martigny, it entered the Rhone, and did no further damage ; but some bodies of men, who had been drowned above Martigny, were afterwards found at the distance of about thirty miles, floating on the farther side of the Lake of Geneva, near Vevey. The waters, on escaping from the lake, intermixed with mud and rock, swept along, for the first four miles, at the rate of above twenty miles an hour; and Mr. Escher, the engineer, calculated that the flood furnished three hundred thousand cubic feet of water every second, an efflux which is five times greater than that of the Rhine below Basle. Now, if part of the lake had not been gradually drained off, the flood would have been nearly double, approaching in volume to some of the largest rivers in the world. It is evident, therefore, that when we are speculating on the excavating force which run- ning water may have exerted in any particular valley, the most important question is not the volume of the existing stream, nor the present levels of the river-channel, nor the size of the gravel, but the probability of a succession of floods, at some period since the time when some of the land in question may have been first elevated above the bosom of the sea. For several months after the debacle of 1818, the Dranse, having no settled channel, shifted its position continually from one side to the other of the valley, carrying away newly-erected bridges, undermining houses, and continuing to be charged with as large a quantity of earthy matter as the fluid could hold in suspension. I visited this valley four months after the flood, and was witness to the sweeping away of a bridge, and the undermining of part of a house. The greater part of the ice-barrier was then standing, presenting a vertical cliff, one hundred and fifty feet high, like the lava-currents of Etna or Auvergne, intersected by a river. Inundations, precisely similar, are recorded to have occurred at former periods in this district, and from the same cause. In 1595, for example, a lake burst, and the waters, descending with irresistible fury, destroyed the town of Martigny, where Ch. XL] FLOOD OF THE A\lO AT TIVOLT. 225 from sixty to eighty persons perished. In a similar flood, fifty years before, one hundred and forty persons were drowned. Flood at Tivoli, 1826. We shall conclude with one more example, derived from a land of classic recollections, the ancient Tibur, and which, like all the other inundations to which we have alluded, occurred within the present century. The younger Pliny, it will be remembered, describes a flood on the Anio, which destroyed woods, rocks, and houses, with the most sumptuous villas and works of art *. For four or five centu- ries consecutively, this headlong stream, as Horace truly called it, has often remained within its bounds, and then, after such long intervals of rest, at different periods inundated its banks again, and widened its channel. The last of these catastrophes happened 15th Nov. 1826, after heavy rains, such as produced the floods before alluded to in Scotland. The waters appear also to have been impeded by an artificial dike, by which they were separated into two parts, a short distance above Tivoli. They broke through this dike, and leaving the left trench dry, precipitated themselves, with their whole weight, on the right side. Here they undermined, in the course of a few hours, a high cliff, and widened the river's channel about fifteen paces. On this height stood the church of St. Lucia, and about thirty- six houses of the town of Tivoli, which were all carried away, presenting, as they sank into the roaring flood, a terrific scene of destruction to the spectators on the opposite bank. As the foundations were gradually removed, each building, some of them edifices of considerable height, was first traversed with numerous rents, which soon widened into large fissures, until at length the roofs fell in with a crash, and then the walls sank into the river, and were hurled down the cataract below [-. The destroying agency of the flood came within two hundred yards of the precipice on which the beautiful temple of Vesta stands ; but fortunately this precious relic of antiquity was * Lib. viii., Epist. 17. f When at Tivoli, in 1S29, I received this account from eye-witnesses of the event. VOL, I. Q 226 FLOOD OF THE ANIO AT TIVOLI. [Ch, XI. spared, while the wreck of modern structures was hurled down the abyss. Vesta, it will be remembered, in the heathen my- thology, personified the stability of the earth ; and when the Samian astronomer, Aristarchus, first taught that the earth revolved on its axis, and round the sun, he was publicly ac- cused of impiety, " for moving the everlasting Vesta from her place." Playfair * observed that when Hutton ascribed insta- bility to the earth's surface, and represented the continents which we inhabit as the theatre of incessant change and move- ment, his antagonists, who regarded them as unalterable, as- sailed him, in a similar manner, with accusations founded on religious prejudices. We might appeal to the excavating power of the Anio as corroborative of one of the most contro- verted parts of the Huttonian theory ; and if the days of omens had not gone by, the geologists who now worship Vesta might regard the late catastrophe as portentous. We may, at least, recommend the modern votaries of the goddess to lose no time in making a pilgrimage to her shrine, for the next flood may not respect the temple. * Illustr. of Hutt. Theory, 3, p. 147. CHAPTER XII. Difference between the transporting power of springs and rivers Many springs carry matter from below upwards Mineral ingredients most abundant in springs Connexion of mineral waters with volcanic phenomena Calcareous springs Travertin of the Elsa Baths of San Vignone and of San Filippo, near Radicofani Spheroidal structure in travertin, as in English magnesian limestone Bulicami of Viterbo Lake of the Solfatara, near Rome Tra- vertin at Cascade of Tivoli Ferruginous Springs Cementing and colouring property of iron Brine Springs Carbonated Springs Disintegration of Auvergue granite Caverns in limestone Petroleum Springs Pitch Lake of Trinidad. MINERAL SPRINGS. Difference between the transporting power of springs and rivers. We have hitherto considered the destroying and transport- ing power of those atmospheric waters which circulate on the surface of the land ; but another portion, which sink deep into the earth, present phenomena essentially different in character. Rivers, as we have seen, remove earthy matter from higher to lower levels, but springs not only effect this purpose, but some- times, like volcanos, carry matter from below upwards. Almost all springs are impregnated with some foreign ingredients, which render them more agreeable to our taste, and more nutri- tive than pure rain water ; but as their mineral contents are in a state of chemical solution, they rarely, even when in great abundance, affect the clearness of the water, and for this reason we are usually unconscious of the great instrumentality of these agents in the transfer of solid matter from one part of the globe to another. The specific gravity of spring water being greater than that of rain, it augments the carrying power of rivers, enabling them to bear down a greater quantity of matter in mechanical suspension towards the sea. Springs, both cold and thermal, rise up beneath the waters of lakes and seas, as Q 2 228 ORIGIN OF THERMAL SPRINGS. [Ch. Xll. well as in different parts of the land, and must often greatly modify the mineral character of subaqueous deposits. Mineral ingredients most abundant in Springs. The num- ber of metals, earths, acids, and alkalies, held in solution by different springs, comprehends a considerable portion of all known substances, and recent observations have tended con- tinually to augment the list ; but those alone which are most abundant, need be regarded as of geological importance. These are lime, iron, magnesia, silica, alumine, soda, and the carbonic and sulphuric acids. Besides these, springs of petroleum, or liquid bitumen, and its various modifications, such as mineral pitch, naphtha, and asphaltum, are largely distributed over the surface of the earth, but usually in close connexion with volcanos. Connexion of mineral waters with volcanic phenomena. The relation, indeed, of almost all springs impregnated copi- ously with mineral matter, to the sources of subterranean heat, seems placed beyond all reasonable doubt by modern research. Mineral waters, as they have been termed, are most abundant in regions of active volcanos, or where earthquakes are most frequent and violent. Their temperature is often very high, and has been known to be permanently heightened or lowered by the shock of an earthquake. The volume of water also given out has been sometimes affected by the same cause. With the exception of silica, the minerals entering most abundantly into thermal waters do not seem to differ from those in cold springs. There is, moreover, a striking analogy between the earthy matters evolved in a gaseous state by volcanos, and those wherewith springs in the same region are impregnated ; and when we proceed from the site of active to that of extinct volcanos, we find the latter abounding in precisely the same kind of springs. Where thermal and mineral waters occur far from active or extinct volcanos, some great internal derange- ment in the strata almost invariably marks the site to have been at some period, however remote, the theatre of violent earthquakes, Ch. XII.] CALCAREOUS SPRINGS. 229 Oriyin of Springs. Springs may, in general, be ascribed to the percolation of rain-water through porous rocks, which, meeting at last with argillaceous strata, is thrown out to the surface. But, in all likelihood, they sometimes descend by fissures, even to the regions of subterranean heat. Michell, in 1760, suggested that those pent-up volcanic vapours which cause earthquakes, penetrate also through rents and cavities, and drive up water impregnated with sulphurous and other matters, whereby springs are charged with their mineral ingre- dients. Nor is it by any means improbable, that the same power which when intense is able to lift up a column of lava many thousand feet in height, should even in its more languid state be capable of raising to the surface considerable quantities of water from the interior. But as the geographical limits of mineral waters are not confined to volcanic regions, being co- extensive with the whole globe, as far as is hitherto known, we must consider them apart, and in their connexion with rivers rather than volcanos. We might divide the consideration of springs, like that of rivers, into their destroying and repro- ductive agency ; but the former class of effects being chiefly subterranean are beyond the reach of our observation ; while their reproductive power consists chiefly in augmenting the quantity of matter deposited by rivers in deltas, or at the bot- tom of the sea. We shall, therefore, arrange the facts of geo logical interest, respecting mineral springs, under the head of the different ingredients which predominate in their waters. CALCAREOUS SPRINGS. OUR first attention is naturally directed to springs which are highly charged with calcareous matter ; for these produce a variety of phenomena of much interest to the geologist. It is well known that rain-water has the property of dissolving the calcareous rocks over which it flows, and by these means, matter is often supplied for the earthy secretions of testacea, and for the growth of certain plants on which they feed, in the smallest ponds and rivulets. But many springs hold so much carbonic 230 CALCAREOUS SPRINGS. [Ch. XII. acid in solution, that they are enabled to dissolve a much larger quantity of calcareous matter than rain-water ; and when the acid is dissipated in the atmosphere, the mineral ingredients are slowly thrown down in the form of tufa or travertin. Auvergne. Calcareous springs, although most abundant in limestone districts, are by no means confined to them, but flow out indiscriminately from all rock formations. In Central France, a district where the primary rocks are unusually des- titute of limestone, springs copiously charged with carbonate of lime rise up through the granite and gneiss. Some of these are thermal, and probably derive their origin from the deep source of volcanic heat, once so active in that region. One of these springs, at the northern base of the hill upon which Cler- mont is built, issues from volcanic peperino, which rests on granite. It has formed, by its incrustations, an elevated mound of solid travertin, or calc-sinter, as it is sometimes called, two hundred and forty feet in length, and, at its termination, six- teen feet high, and twelve wide. Another incrusting spring, in the same department, situated at Chaluzet, near Pont Gibaud, rises in a gneiss country, at the foot of a regular vol- canic cone, at least twenty miles from any calcareous rock. Some masses of tufaceous deposit, produced by this spring, have an oolitic texture. Valley of the Elsa. If we pass from the volcanic district of France to that which skirts the Apennines in the Italian penin- sula, we meet with innumerable springs, which have precipitated so much calcareous matter, that the whole ground in some parts of Tuscany is coated over with travertin, and sounds hollow beneath the foot. In other places in the same country, compact rocks are seen descending the slanting sides of hills, very much in the manner of lava-currents, except that they are of a white colour, and terminate abruptly when they reach the course of a river. These consist of the calcareous precipitate of springs, some of them still flowing, while others have disappeared or changed their position. Such masses are frequent on the slope of the Ch. XII.] TRAVERTIN OF SAN VIGNONE* 231 hills which bound the valley of the Elsa, one of the tributaries of the Arno, which flows near Colle, through a valley several hundred feet deep, shaped out of a lacustrine formation, con- taining fossil shells of existing species. The travertin is uncon- formable to the lacustrine beds, and its inclination accords with the slope of the sides of the valley *. The Sena, and several other small rivulets which feed the Elsa, have the property of lapidifying wood and herbs ; and, in the bed of the Elsa itself, aquatic plants, such as charae, which absorb large quantities of carbonate of lime, are very abundant. Carbonic acid is also seen in the same valley, bub- bling up from many springs, where no precipitate of tufa is observable. Targioni, who in his travels has mentioned a great number of mineral waters in Tuscany, found no difference be- tween the deposits of cold and thermal springs. They issue sometimes from the older Apennine limestone, shale, and sand- stone, while, in other places, they flow from more modern deposits ; but, even in the latter case, their source may pro- bably be in, or below the older series of strata. Baths of San Vignone. Those persons who have merely seen the action of petrifying waters in our own country, will not easily form an adequate conception of the scale on which the same process is exhibited in those regions which lie nearer to the modern centres of volcanic disturbance. One of the most striking examples of the rapid precipitation of carbonate of lime from thermal waters occurs in the hill of San Vignone in Tuscany, at a short distance from Radicofani, and only a few hundred yards from the high road between Sienna and Rome. The spring issues from near the summit of a rocky hill, about one hundred feet in height. The top of the hill is flat, and stretches in a gently-inclined plateau to the foot of Mount Amiata, a lofty eminence, which consists in great part of volcanic products. The fundamental rock, from which the spring issues, is a black slate, with serpentine (6, b, 6, diagram * One of the finest examples of these which I saw, was at the Molino delle Caldane, near Colle. 232 TRAVERTIN OF SAN VIGNONE. [Ch. XII. 4) belonging to the older Apennine formation. The water is Baths of San Fir/none. No. 4. Section of travertin, San I'ignone. hot, has a strong taste^ and, when not in very small quantity, is of a bright green colour. So rapid is the deposition near the source, that in the bottom of a conduit-pipe for carrying off the water to the baths, inclined at an angle of 30, half a foot of solid travertin is formed every year. A more compact rock is produced where the water flows slowly, and the precipi- tation in winter is said to be more solid and less in quantity by one-fourth than in summer. The rock is generally white : some parts of it are compact, and ring to the hammer ; others are cellular^ and with such cavities as are seen in the carious part of bone or the siliceous meuliere of the Paris basin. A portion of it also below the village consists of long vegetable tubes. Sometimes the travertin assumes precisely the bo- troidal and mammillary forms, common to similar deposits, in Auvergne, of a much older date, hereafter to be mentioned ; and, like them, it often scales off in thin, slightly-undulating layers. A large mass of travertin (c, diagram 4) descends the hill from the point where the spring issues, and reaches to the dis- tance of about half a mile east of San Vignone. The beds take the slope of the hill at about an angle of 6, and the planes of stratification are perfectly parallel. One stratum, composed of many layers, is of a compact nature and fifteen feet thick ; it serves as an excellent building stone, and a mass of fifteen feet in length was., in 1828, cut out for the new bridge Ch. XII.] TRAVERTIN OF SAN FIL1PPO. 233 over the Orcia. Another branch of it (a, diagram 4) descends to the west, for two hundred and fifty feet in length, of vary- ing thickness,, but sometimes two hundred feet deep ; it is then cut off by the small river Orcia, precisely as some glaciers in Switzerland descend into a valley till their progress is suddenly arrested by a transverse stream of water. The abrupt termination of the mass of rock at the river, when its thickness is undiminished, clearly shows that it would proceed much farther if not arrested by the stream, over which it impends slightly. But it cannot encroach upon the channel of the Orcia, being constantly undermined, so that its solid fragments are seen strewed amongst the alluvial gravel. How- ever enormous, therefore, the mass of solid rock may appear which has been given out by this single spring, we may feel assured that it is insignificant in volume, when compared to that which has been carried to the sea since the time when it began to flow. What may have been the length of that period of time, we have no data for conjecturing. In quarrying the travertin, Roman tiles have been sometimes found at the depth of five or six feet. Baths of San Filippo. On another hill, not many miles from that last mentioned, and also connected with Mount Amiata, the summit of which is about three miles distant, are the celebrated baths of San Filippo. The subjacent rocks consist of alternations of black slate, limestone, and serpen- tine, of highly inclined strata, belonging to the Apennine formation ; and, as at San Vignone, near the boundary of a tertiary basin of marine origin, consisting chiefly of blue argil- laceous marl. There are three warm springs here, containing carbonate and sulphate of lime, and sulphate of magnesia. The water which supplies the bath falls into a pond, where it has been known to deposit a solid mass thirty feet thick, in about twenty years*. A manufactory of medallions in basso- relievo is carried on at these baths. The water is conducted by canals into several pits, in which it deposits travertin and * Dr. Grosse, on the Baths of San Filippo. Ed. Phil, Journ. v. 2, p. 292. 234 MEDALLIONS OF SAN FILIPPO. [Ch. XII. crystals of sulphate of lime. After being thus freed from its grosser parts, it is conveyed by a tube to the summit of a small chamber, and made to fall through a space of ten or twelve feet. The current is broken in its descent by numerous crossed sticks, by which the spray is dispersed around upon certain moulds, which are rubbed lightly over with a solution of soap, and a deposition of solid matter like marble is the result, yielding a beautiful cast of the figures formed in the mould *. The geologist may derive from these experiments considerable light, in regard to the high inclination at which some semicrystalline precipitations can be formed; for some of the moulds are disposed almost perpendicularly, yet the deposition is nearly equal in all parts. A hard stratum of stone about a foot in thickness, is ob- tained from the waters of San Filippo in four months ; and, as the springs are powerful, and almost uniform in the quan- tity given out, we are at no loss to comprehend the magnitude of the mass which descends the hill, which is a mile and quarter in length and the third of a mile in breadth, in some places attaining a thickness of two hundred and fifty feet at least. To what length it might have reached, it is impossible to conjecture, as it is cut off, like the travertin of San Vig- none, by a small stream, where it terminates abruptly. The remainder of the matter held in solution is carried on probably to the sea. Spheroidal structure in travertin. But what renders this recent calcareo-magnesian limestone of peculiar interest to the geologist, is the spheroidal forms which it assumes, offering so striking an analogy, on the one hand, to the concentric struc- ture displayed in the calcareous travertin of the cascade of Tivoli, and on the other, to the spheroidal forms of the Eng- lish magnesian limestone of Sunderland. Between this latter and many of the appearances exhibited at San Filippo, and several other recent deposits of the same kind in Italy, there is every feature of resemblance ; the same combination of con- * Dr, Grosse, on the Baths of San Filippo, Ed, Phil. Journ., v. 2, p. 297. Ch. XII.] SPHEROIDAL STRUCTURE. 235 centric and radiated structure, with small undulations in each concentric ring, occasional interferences of one circle with an- other, and a small globular structure subordinate to the large spheroidal, with frequent examples of laminae passing off from the external coating of a spheroid into layers parallel to the general plane of stratification. There are also cellular cavities and vacuities in the rock, constituting what has been termed a honeycombed texture. The lamination of some of the con- centric masses of San Filippo is so minute, that sixty may be counted in the thickness of an inch. Yet, notwithstanding these marks of gradual and successive deposition, the sym- metry and magnitude 'of many of the spheroidal forms might convey the idea, that the whole was the result of chemical action, simultaneously operating on a great mass of matter. Compared to that of English magnesian limestone. The concretionary forms of our magnesian limestone have been supposed by some to have been superinduced after the com- ponent parts of the rock had been brought together in stra- tiform masses ;, but a careful comparison of those older rocks with the numerous travertins now in progress of formation in Italy leads the observer to a different conclusion. Such a structure seems to be the result of gradual precipitation, and not of subsequent re -arrangement of the particles *. Each * The structure of the English magnesian limestone has been described, in an elaborate and profound paper on that formation, by Professor Sedgwick. Geol. Trans., vol. 3, second series, part i., p. 37. Examples of almost all the modifications of concretionary arrangement, together with the brecciated and honeycombed structure to which he alludes, may be found either in the deposits of travertin springs in various parts of Italy, or in the subaqueous travertins of Auvergne and Sicily, the former of lacustrine, the latter of submarine origin. These will be alluded to in their proper places, and I shall merely observe here, that, after examining these more recent deposits, I visited Sunderland, and recognized a degree of identity in the various and complicated forms there assumed by the magnesian limestone, which satisfied me that the circumstances under which they were formed must have been perfectly analogous to those under which the mineral springs of volcanic countries are now giving birth to calcareous, calcereo-mag- nesian, and calcereo-siliceous rocks. 236 CALCAREOUS PRECIPITATES [Ch. XII. minute particle of foreign matter, a reed, or the fragment of a shell, forms a nucleus, around which accessions of new lamina? are formed, until spheroids and elongated cones, from a few inches to several feet in diameter, are produced; for, as the precipitate is arranged by the force of chemical affinity, and not of gravity, the different layers continue of the same thick- ness, and preserve the original form of the nucleus. Bulicami of Viterbo. We must not attempt to describe all the places in Italy where the constant formation of limestone may be seen, as on the Silaro, near Paestum, on the Velino at Terni, and near the Bulicami, or hot baths in the vicinity of Viterbo. About a mile and a half north of the latter town, in the midst of a sterile plain of volcanic sand and ashes, a monticule is seen, about twenty feet high and five hundred yards in circumference, entirely composed of concretionary travertin. The lamina? are extremely thin, and their minute undulations are so arranged, that the whole mass has at once a concentric and radiated structure. This rock has been largely quarried for lime, and much of it appears to have been removed. It seems to have been formed by a small jet or fountain of calcareous water, which continued to rise through the mound of travertin, which it gradually raised by overflow- ing from the summit. A spring of hot water still issues in the neighbourhood, which is conveyed to an open tank, used as a bath, the bottom and sides of which, as well as the open conduit which conveys the water, are encrusted with tra- vertin. Campacjna di Roma. The country around Rome, like many parts of the Tuscan States already referred to, has been at some former period the site of numerous volcanic eruptions ; and the springs are still copiously impregnated with lime, carbonic acid, and sulphuretted hydrogen. A hot spring has lately been dis- covered near Civita Vecchia, by Riccioli, which deposits alter- nate beds of a yellowish travertin, and a white granular rock, not distinguishable, in hand specimens, either in grain, colour, Ch. XII.] OF THE CAMPAGNA DI ROMA. 237 or composition, from statuary marble. There is a passage between this and ordinary travertin. The mass accumulated near the spring is in some places about six feet thick *. Lake of the Solfatara. In the Campagna, between Rome and Tivoli, is the lake of the Solfatara, called also Lago di Zolfo, (lacus albula,) into which flows continually a stream of tepid water, from a smaller lake situated a few yards above it. The water is a saturated solution of carbonic acid gas, which j escapes from it in such quantities in some parts of its surface, j that it has the appearance of being actually in ebullition. ' I have found by experiment/ says Sir Humphry Davy, * that the water taken from the most tranquil part of the lake, even after being agitated and exposed to the air, contained in solu- tion more than its own volume of carbonic acid gas, with a very small quantity of sulphuretted hydrogen. Its high tem- perature, which is pretty constant at 80 of Fahr., and the quantity of carbonic acid that it contains, render it peculiarly fitted to afford nourishment to vegetable life. The banks of tra- vertin are every where covered with reeds, lichen, confervas, and various kinds of aquatic vegetables ; and at the same time that the process of vegetable life is going on, the crystallizations of the calcareous matter, which is every where deposited in conse- quence of the escape of carbonic acid, likewise proceed. There is, I believe, no place in the world where there is a more striking example of the opposition or contrast of the laws of animate and inanimate nature, of the forces of inorganic che- mical affinity, and those of the powers of life f.' The same observer informs us, that he fixed a stick on a mass of travertin covered by the water in May, and in the April following he had some difficulty in breaking, with a * I did not visit this spring myself, but Signer Riccioli, whose acquaintance with the geology of the environs of Rome is well known, favoured me with an inspection of a suite of specimens collected from the spot. Brocchi, a few years before his death, visited the locality in company with Signor Riccioli, and was much struck with the phenomenon, of which he had intended to publish a description, f Consolations in Travel, p. 123125. 238 TRAVERTIN OF TIVOLI. [Ch. XII. sharp-pointed hammer, the mass which adhered to the stick, and which was several inches in thickness. The upper part was a mixture of light tufa and the leaves of confervas : below this was a darker and more solid travertin, containing black and decomposed masses of confervae ; in the inferior part the travertin was more solid, and of a grey colour, but with cavities probably produced by the decomposition of vegetable matter *. The stream which flows out of this lake fills a canal about nine feet broad and four deep, and is conspicuous in the land- scape by a line of vapour which rises from it. It deposits tufa in this channel, and the Tiber probably receives from it, as well as from numerous other streams, much carbonate of lime in solution, which contributes to the rapid growth of its delta. A large portion of the most splendid edifices of ancient and modern Rome are built of travertin, derived from the quarries of Ponte Leucano, where there has evidently been a lake at a remote period, on the same plain as that already described. But as the consideration of these would carry us beyond the times of history, we shall conclude with one more example of the calcareous deposits of this neighbourhood, those on the Anio. Travertin of Tivoli. The waters of the Anio incrust the reeds which grow on its banks, and the foam of the cataract of Tivoli forms beautiful pendant stalactites ; but, on the sides of the deep chasm into which the cascade throws itself, there is seen an extraordinary accumulation of horizontal beds of tufa and travertin, from four to five hundred feet in thick- ness. The following seems the most probable explanation of their formation in this singular position. The Anio flows through a deep, irregular fissure or gorge in the Apennine limestone, which may have originated from subterranean movements, like many others of which we shall speak when treating of earthquakes. In this deep narrow channel there existed many small lakes, three of which have been destroyed * Consolations in Travel, p. 127. Ch. XII.] TRAVERTIN OF TIVOLI. 239 since the time of history, by the erosive action of the torrent, the last of them having remained down to the sixth century of our era. We may suppose a similar lake of great depth to have ex- isted at some remote period at Tivoli, and that, into this, the waters, charged with carbonate of lime, fell from a height inferior to that of the present cascade. Having, in their pas- sage through the upper lakes, parted with their sand, pebbles, and coarse sediment, they only introduced into this lower pool drift-wood, leaves, and other buoyant substances. In seasons when the water was low, a deposit of ordinary tufa, or tra- vertin, formed along the bottom ; but at other times, when the torrent was swollen, the pool must have been greatly agitated, and every small particle of carbonate of lime which was pre- cipitated must have been whirled round again and again in various eddies, until it acquired many concentric coats, so as to resemble oolitic grains. If the violence of the motion be sufficient to cause the globule to be suspended for a sufficient length of time, it would grow to the size of a pea, or much larger. Small fragments of vegetable stems being incrusted on the sides of the stream, and then washed in, would form the nucleus of oval globules, and others of irregular shapes would be produced by the resting of fragments for a time on the bot- tom of the basin, where, after acquiring an unequal thickness of travertin on one side, they would again be set in motion. Sometimes globules, projecting above the general level of a stratum, would attract, by chemical affinity, other matter in the act of precipitation, and thus growing on all sides, with the exception of the point of contact, might at length form spheroids nearly perfect and many feet in diameter. Masses might increase above and below, so that a vertical section might afterwards present the phenomenon so common at Tivoli, where the nucleus of some of the concentric circles has the appearance of having been suspended, without support, in the water, until it became a spheroidal mass of great dimensions. The section obtained of these deposits, about four hundred 240 TRAVERTIN OF TIVOLI. [CIi. XII, feet thick, immediately under the temples of Vesta and the Sibyl, displays some spheroids which are from six to eight feet in diameter , each concentric layer being about the eighth of an inch in thickness. The annexed diagram exhibits about four- No. 5. Section of Spheroidal Concretionary Travertin under the Cascade of Tivo/i. teen feet of this immense mass, as seen in the path cut out of the rock in descending from the temple of Vesta to the Grotto di Nettuno*. The beds (a a, diagram No. 5) are of hard tra- * I have not attempted to express in this drawing the innumerable thin layers of which these magnificent spheroids are composed, but the lines given mark some of the natural divisions into which they are separated by minute variations in the size or colour of the laminae. The undulations also are much smaller, iu propor- tion to the whole circumference, than is expressed in the diagram. Ch. XII.j CALCAREOUS TUfA. 241 vertin and soft tufa; below them is a pisolite (6), the globules being of different sizes : underneath this appears a mass of con- cretionary travertin (cc), some of the spheroids being of the above-mentioned extraordinary size. In some places (as at d) there is a mass of amorphous limestone, or tufa, surrounded by concentric layers. At the bottom is another bed of pisolite (b), in which the small nodules are about the size and shape of beans, and some of them of filberts, intermixed with some smaller oolitic grains. In the tufaceous strata, wood is seen converted into a light tufa. It is probable that the date of the greater portion of this calcareous formation may be anterior to the era of history, for we know that there was a great cascade at Tivoli in very an- cient times ; but, in the upper part of the travertin, is shown the hollow left by a wheel, in which the outer circle and the spokes have been decomposed, and the spaces which they filled have been left void. It seems impossible to explain the posi- tion of this mould, without supposing that the wheel was im- bedded before the lake was drained. Calcareous Springs in the Caucasus. Our limits do not permit us to enter into minute details respecting the various limestones to which springs in different countries are continu- ally giving birth. Pallas, in his journey along the Caucasus, a country now subject, from time to time, to be rent and fis- sured by violent earthquakes, enumerates a great many hot springs, which have deposited monticules of travertin precisely analogous in composition and structure to those of the baths of San Filippo and other localities in Italy. When speaking of the tophus-stone, as he terms these limestones, he often observes that it is snow-white, a description which is very applicable to the newer part of the deposit at San Filippo, where it has not become darkened by weathering. In many localities in the regions between the Caspian and Black seas, where subterra- nean convulsions are frequent, travellers mention calc-sinter as an abundant product of hot springs. Near the shores of the Lake Urmia (or Maragha), for example, a marble is rapidly VOL. I. R 242 CALCAREOUS TUFA. [Ch. XII. deposited from a thermal spring, which is much used in orna- mental architecture *. Calcareous deposits. We might mention springs of the same kind in Calabria and Sicily, and indeed in almost all regions of volcanos and earthquakes which have been carefully investi- gated. In the limestone districts of England, as on Inglebo- rough Hill, in Yorkshire, we often see walls entirely constructed of calcareous tufa, enclosing terrestrial shells and vegetables, and similar tufa still continues to be formed in that district. The growth of stalactites, also, and stalagmites in caverns and grottos, is another familiar example of calcareous precipitates. To the solvent power of water, surcharged with carbonic acid, and percolating various winding rents and fissures, we may ascribe those innumerable subterranean cavities and winding passages which traverse the limestone in our own and many other countries. Dr. Buckland has observed, that caves in limestone are usually connected with fissures in the rock in which they exist f . The quantity of calcareous rock which results from mineral waters in volcanic regions, conspicuous as it is, must be con- sidered as insignificant, in comparison to that which is conveyed by rivers to the sea ; and our inability to observe subaqueous accumulations resulting from this source, is one of many causes of our inadequate conception of the changes now in progress on the earth's surface. Coral reefs of the Pacific. It has often been supposed, that the greater part of the coral reefs in the Indian and Pacific ocea"ns were based on submarine volcanos, which seems indi- cated by the circular shape so frequently assumed by them ; but perhaps a still stronger argument in favour of this theory might be deduced from the great abundance of carbonate of lime required for the rapid growth of zoophytic and shelly limestones, an abundance which could only be looked for where there are active volcanos and frequent earthquakes, as amongst the isles of the South Pacific. We may confidently * Hoff, Geschichtej&c., vol. ii. p. 114. f Rel. Dil., p. 5, note. Ch. XII.] GYPSEOUS AND SILICEOUS SPRINGS. 243 infer, that the development of organic life would be promoted in corals, sponges, and testaceous mollusca, by the heat, car- bonic acid, lime, silica, and other mineral ingredients in a state of solution, given out by submarine springs, in the same man- ner as the vegetation is quickened in the lake of the Solfatara, in the Campagna di Roma, before described. GYPSEOUS SPRINGS. All other mineral ingredients wherewith springs in general are impregnated, are insignificant in quantity in comparison to lime, and this earth is most frequently combined with carbonic acid. But as sulphuric acid and sulphuretted hydrogen are very frequently supplied by springs, we must presume that gyp- sum is now deposited largely in many seas and lakes. The gyp- seous precipitates, however, hitherto known on the land, appear to be confined to a very few springs. Those at Baden, near Vienna, which feed the public bath, may be cited as examples Some of these supply, singly, from six hundred to one thou- sand cubic feet of water per hour, and deposit a fine powder, composed of a mixture of sulphate of lime, with sulphur and muriate of lime*. SILICEOUS SPRINGS. Azores.' In order that water should hold a very large quantity of silica in solution, it seems necessary that it should be raised to a high temperature f ; and as it may retain a greater heat under the pressure of the sea than in the atmo- sphere, submarine springs may, perhaps, be more charged with silex than any to which we have access. The hot springs of the Valle das Furnas, in the Island of St. Michael, rising through volcanic rocks, precipitate vast quantities of siliceous sinter, as it is usually termed. Around the circular basin of the largest spring, called * the Caldeira,' which is between twenty and thirty feet in diameter, alternate layers are seen of * Prevost, Essai sur la Constitution Physique du Bassin de Vienue, p. 10. f Daubeny, on Volcanos, p. 222. R 2 244 GEYSERS OF ICtiLANI). [Cli. XI T * a coarser variety of sinter mixed with clay, including grass, ferns, and reeds, in different states of petrifaction. Wherever the water has flowed, sinter is found rising in some places eight or ten inches above the ordinary level of the stream. The herb- age and leaves, more or less incrusted with silex, exhibit all the successive steps of petrifaction, from the soft state to a com- plete conversion into stone ; but, in some instances, alumina, which is likewise deposited from the hot waters, is the mineral- izing material. Branches of the same ferns which now flourish in the island, are found completely petrified, preserving the same appearance as when vegetating, except that they acquire an ash-gray colour. Fragments of wood, and one entire bed from three to five feet in depth, composed of reeds now com- mon in the island, have become completely mineralized. The most abundant variety of siliceous sinter occurs in layers from a quarter to half an inch in thickness, accumulated on each other often to the height of a foot and upwards, and con- stituting parallel, and for the most part horizontal, strata many yards in extent. This sinter has often a beautiful semi-opal- escent lustre. One of the varieties differs from that of Ice- land and Ischia in the larger proportion of water it contains, and in the absence of alumina and lime. A recent breccia is also in the act of forming, composed of obsidian, pumice, and scoria?, cemented by siliceous sinter *. Geysers of Iceland. But the hot springs in various parts of Iceland, particularly the celebrated geysers, afford the most remarkable example of the deposition of silex. The circular reservoirs into which the geysers fall, are filled in the middle with a variety of opal, and round the edges with sinter. The plants, incrusted with the latter substance, have much the same appearance as those incrusted with calcareous tufa in our own country. The solution of the silex is supposed to be promoted by the presence of some mineral alkali. In some of the thermal waters of Iceland a vesicular rock is formed, containing por- tions of vegetables, more or less completely silicified. Amongst * Dr. Webster, on the Hot Springs of Furnas, Ed. Phil, Jouru. vol. vi. p. 306. Ch. XII.] FERRUGINOUS SPRINGS. 245 the various products ako of springs in this island, is that ad- mixture of clay and silica, called tripoli. Ischia. It has been found, by recent analysis, that severa. of the thermal waters of Ischia are impregnated with a certain proportion of silica. Some of the hot vapours of that island are above the temperature of boiling water; and many fissures, near Monte Vico, through which the hot steam passes, are coated with a siliceous incrustation, first noticed by Dr. Thomp- son under the name of fiorite. Ava, 8fc. It has been often stated that the Danube has converted the external part of the piles of Trajan's bridge into silex ; the Irawadi, in Ava, has been supposed, ever since the time of the Jesuit Padre Duchatz, to have the same petrifying power, as has also Lough Neagh, in Ireland. Modern re- searches, however, in the Burman empire, have thrown doubt upon the lapidifying property of the Ava river*; there is cer- tainly no foundation for the story in regard to Lough Neagh, and probably none in regard to the Danube. Mineral waters, even when charged with a small proportion of silica, as those of Ischia, may supply certain species of corals and sponges with matter for their siliceous secretions; but when in a volcanic archipelago, or a region of submarine vol- canos, there are springs so saturated with silica, as those of Iceland and the Azores, we may expect beds of chert or layers and nodules of silex, to be spread out far and wide over the bed of the sea, and interstratified with shelly and calcareous deposits, which may be forming there, or with matter derived from the wasting cliffs or volcanic ejections. FERRUGINOUS SPRINGS. The waters of almost all springs contain some iron in solu- tion ; and it is a fact familiar to all, that many of them are so copiously impregnated with this metal, as to stain the rocks or nerbage through which they pass, and to bind together san(l * Dr. Buckland, Geol. Trans., second series, vol. ii. part 3, j>. 384. 246 BRINE SPRINGS. [Ch, XII. and gravel into solid masses. We may naturally, therefore, conclude that this iron, which is constantly conveyed into lakes and seas from the interior of the earth, and not re- turned again to the land by evaporation in the atmospheric waters, must act as a colouring and cementing principle in the subaqueous deposits now in progress. When we find, therefore, that so many sandstones and other rocks in the sedimentary strata of ancient lakes and seas are bound together or coloured by iron, it presents us with a striking point of analogy between the state of things at very different epochs. In the older for- mations we meet with great abundance of carbonate and sul- phate of iron ; and in chalybeate waters at present, this metal is most frequently in the state of a carbonate, as in those of Tunbridge, for example. Sulphuric acid, however, is often the solvent, which is in many cases derived from the decompo- sition of pyrites. BRINE SPRINGS. Cheshire. So great is the quantity of muriate of soda in some springs, that they yield one-fourth of their weight in salt. They are rarely, however, so saturated, and generally contain, intermixed with salt, carbonate and sulphate of lime, magnesia, and other mineral ingredients. The brine springs of Cheshire are the richest in our country ; those of Barton and Northwich being almost fully saturated. These brine springs rise up through strata of sandstone and red marl, which contain large beds of rock-salt. The origin of the brine, therefore, may be derived in this and many other instances from beds of fossil salt ; but as muriate of soda is one of the products of volcanic emanations and of springs in volcanic regions, the ori- ginal source of salt may be as deep seated as that of lava. Dead Sea. The waters of the Dead Sea contain scarcely anything except muriatic salts, which lends countenance, ob- serves Dr. Daubeny, to the volcanic origin of the surrounding country, these salts being frequent products of volcanic erup- Ch. XII.] CARBONATED SPRINGS. 247 tions. Many springs in Sicily contain muriate of soda, and the ' fiume salso,' in particular, is impregnated with so large a quantity, that cattle refuse to drink of it. If rivers or springs, thus impregnated^ enter a lake or estuary, it is evident that they may give rise to partial precipitates of salt. Auvergne. A hot spring, rising through granite, at Saint Nectaire, in Auvergne, may be mentioned as one of many, con- taining a large proportion of muriate of soda, together with magnesia and other ingredients *. CARBONATED SPRINGS. Auvergne. Carbonic acid gas is very plentifully disengaged from springs in almost all countries, but particularly near active or extinct volcanos. This elastic fluid has the property of decomposing many of the hardest rocks with which it comes in contact, particularly that numerous class in whose compo- sition felspar is an ingredient. It renders the oxide of iron soluble in water, and contributes, as was before stated, to the solution of calcareous matter. In volcanic districts these gaseous emanations are not confined to springs, but rise up in the state of pure gas from the soil in various places. The Grotto delle Cane, near Naples, affords an example, and pro- digious quantities are now annually disengaged from every part of the Limagne d'Auvergne, where it appears to have been developed in equal quantity from time immemorial. As the acid is invisible, it is not observed, except an excavation be made, wherein it immediately accumulates, so that it will extinguish a candle. There are some springs in this district, where the water is seen bubbling and boiling up with much noise, in consequence of the abundant disengagement of this gas. The whole vegetation is affected, and many trees, such as the walnut, flourish more luxuriantly than they would otherwise do in the same soil and climate, the leaves probably absorbing carbonic acid. This gas is found in springs rising through the granite near Clermont, as well as in the tertiary Annales de 1 'Auvergne, tome i. p. 234. 248 CARBONATED SPRIN'GS. [Ch. XII. limestones of the Limagne *. In the environs of Pont-Gibaud, not far from Clermont, a rock belonging to the gneiss forma- tion, in which lead -mines are worked, has been found to be quite saturated with carbonic acid gas, which is constantly disengaged. The carbonates of iron, lime, and manganese are so dissolved, that the rock is rendered soft, and the quartz alone remains unattacked f. Not far off is the small volcanic cone of Chaluzet, which once broke up through the gneiss, and sent forth a lava-stream. Disintegration of granite. The disintegration of granite is a striking feature of large districts in Auvergne, especially in the neighbourhood of Clermont. This decay was called by Dolomieu, 'la maladie du granite;' and the rock may with propriety be said to have the rot, for it crumbles to pieces in the hand. The phenomenon may, without doubt, be ascribed to the continual disengagement of carbonic acid gas from nu- merous fissures. In the plains of the Po, between Verona and Parma, espe- cially at Villa Franca, south of Mantua, I observed great beds of alluvium, consisting chiefly of primary pebbles percolated by spring water, charged with carbonate of lime and carbonic acid in great abundance. They are for the most part in- crusted with calc-sinter ; and the rounded blocks of gneiss, which have all the appearance of solidity,, have been so disin- tegrated by the carbonic acid as readily to fall to pieces. The Po and other rivers, in winding through this plain, might now remove with ease those masses which, at a more remote period, the stream was unable to carry farther towards the sea ; and in this example we may perceive how necessary it is, in rea- soning on the transporting power of running water, to con- sider all the numerous agents which may co-operate, in the lapse of ages, in conveying the wreck of mountains to the 'sea. A granite block might remain stationary for ages, arid defy * Le Coq, Annales de 1' Auvergne. tome i. p. 217. May, 1828, f Ann. Scient. de 1' Auvergne, tome ii. June, 18. 7 9. Ch. XII.] PETROLEUM SPRINGS. 249 the power of a large river ; till at length a small spring may break out, surcharged with carbonic acid, the rock may be decomposed, and a streamlet may transport the whole mass to the ocean. The subtraction of many of the elements of rocks by the solvent power of carbonic acid, ascending both in a gaseous state and mixed with spring-water in the crevices of rocks, must be one of the most powerful sources of those internal changes and re-arrangements of particles so often observed in strata of every age. The calcareous matter, for example, of shells is often entirely removed and replaced by carbonate of iron, pyrites, or silex, or some other ingredient, such as mineral waters usually contain in solution. It rarely happens, except in limestone rocks, that the carbonic acid can dissolve all the constituent parts of the mass ; and for this reason, pro- bably, calcareous rocks are almost the only ones in which great caverns and long winding passages are found. The grottos and subterranean passages in certain lava-currents are due to a different cause, and will be spoken of in another place. PETROLEUM SPRINGS. Springs impregnated with petroleum, and the various mine- rals allied to it, as bitumen, naphtha, asphaltum, and pitch, are very numerous, and are, in many cases, undoubtedly con- nected with subterranean fires, which raise or sublime the more subtle parts of the bituminous matters contained in rocks. Many springs in the territory of Modena and Parma, in Sicily, pro- duce petroleum in abundance ; but the most powerful, perhaps, yet known, are those on the Irawadi, in the Burman empire. In one locality there are said to be five hundred and twenty wells, which yield annually four hundred thousand hogsheads of petroleum*. * Symes, Embassy to Ava, vol. ii. Geol. Trans., Second Scries, vol. ii. part iii. p. 388, 250 PETROLEUM SPRINGS. [Ch. XII. Fluid bitumen is seen to ooze from the bottom of the sea, on both sides of the island of Trinidad, and to rise up to the surface of the water. Near Cape La Braye there is a vortex which, in stormy weather, according to Captain Mallet, gushes out, raising the water five or six feet, and covers the surface for a considerable space with petroleum, or tar ; and the same author quotes Gumilla, as stating in his ' Description of the Orinoco,' that, about seventy years ago, a spot of land on the western coast of Trinidad, near half-way between the capital and an Indian village, sank suddenly, and was immediately replaced by a small lake of pitch, to the great terror of the inhabitants *. Pitch lake of Trinidad. It is probable that the great pitch lake of Trinidad owes its origin to a similar cause ; and Dr. Nugent has justly remarked, that in that district all the cir- cumstances are now combined from which deposits of pitch may have originated. The Orinoco has for ages been rolling down great quantities of woody and vegetable bodies into the surrounding sea, where, by the influence of currents and eddies, they may be arrested and accumulated in particular places. The frequent occurrence of earthquakes and other indications of volcanic action in those parts lend countenance to the opi- nion, that these vegetable substances may have undergone, by the agency of subterranean fire, those transformations and chemical changes which produce petroleum, and may, by the same causes, be forced up to the surface, where, by exposure to the air, it becomes inspissated, and forms the different vari- eties of pure and earthy pitch, or asphaltum, so abundant in the island |. The bituminous shales, so common in geological formations of different ages, as well as many stratified deposits of bitu- men and pitch, seem clearly to attest that, at former periods, springs, in various parts of the world, were as commonly im- pregnated as now with bituminous matter, which was carried * Dr. Nugent, Geol. Trans., vol. i. p. 69. t Ibid., p. 67. Ch. XII.] PETROLEUM SPRINGS. 251 down by rivers into lakes and seas. We may indeed remark generally, that a large portion of the finer particles and the more crystalline substances found in sedimentary rocks of different ages are composed of the same elements as are now held in solution by springs, while the coarser materials bear an equally strong resemblance to the alluvial matter in the beds of exist- ing torrents and rivers. CHAPTER XIII. Reproductive effects of running water Division of Deltas into lacustrine, medi- terranean, and oceanic Lake deltas Growth of the delta of the Rhone in the Lake of Geneva Chronological computations of the age of deltas Recent deposits in Lake Superior Deltas of inland seas Rapid shallowing of the Baltic Arguments for and against the hypothesis of Celsius Elevated beaches on the coast of Sweden Marine delta of the Rhone Various proofs of its increase Stony nature of its deposits Delta of the Po, Adige, Isonzo, and other rivers entering the Adriatic Rapid conversion of that gulf into land Mineral characters of the new deposits Delta of the Nile Its increas since the time of Homer Its growth why checked at present. REPRODUCTIVE EFFECTS OF RUNNING WATER. We have hitherto considered the destroying agency of running water, as exhibited in the disintegration of rocks and transpor- tation of matter from higher to lower levels. It remains for us to examine the reproductive effects of the same cause. The aggregate amount of matter accumulated in a given time at the mouths of rivers, where they enter lakes or seas, affords clearer data for estimating the energy of the excavating power of running water on the land, than the separate study of the operations of the same cause in the countless ramifications into which every great system of valleys is divided. We shall proceed to select some of the leading facts at present ascer- tained respecting the growth of deltas, and shall then offer some general observations on the quantity of subaqueous sediment transported by rivers, and on the manner of its distribution. Division of deltas into lacustrine, mediterranean, and oceanic. Deltas may be divided into, first, those which are formed in lakes ; secondly, those formed in inland seas ; and thirdly, those formed on the borders of the ocean. The most characteristic distinction between the lacustrine and marine deltas consists in the nature of the organic remains, which become imbedded in their deposits, for, in the case of a lake, Ch. XIII.] LAKE OF GENEVA. 253 it is obvious that these must consist exclusively of such genera of animals as inhabit the land or the waters of a river or lake ; whereas, in the other case, there will be an admixture and most frequently a predominance of animals which inhabit salt water. In regard, however, to the distribution of inorganic matter, the deposits of lakes and inland seas are formed under very ana- logous circumstances and may be contradistinguished from those on the shores of the great ocean, where the tides co- operating with currents give rise to a distinct class of pheno- mena. In lakes and inland seas, even of the largest dimen- sions, the tides are almost insensible, and the currents are, for the most part, inconsiderable, although some striking excep- tions to this rule will be mentioned when we treat of tides and currents. DELTAS IN LAKES. Lake of Geneva. It is natural to begin our examination with an inquiry into the new deposits in lakes, as they exem- plify the first reproductive operations in which rivers are en- gaged when they convey the detritus of rocks and the ingre- dients of mineral springs from mountainous regions. The accession of new land at the mouth of the Rhone, at the upper end of the Lake of Geneva, or the Leman Lake, presents us with an example of a considerable thickness of strata, which have accumulated since the historical era. This sheet of water is about thirty-seven miles long, and its breadth is from two to eight miles. The shape of the bottom is very irre- gular, the depth having been found, by late measurements, to vary from twenty to one hundred and sixty fathoms*. The Rhone, where it enters at the upper end, is turbid and disco- loured ; but its waters, where it issues at the town of Geneva, are beautifully clear and transparent. An ancient town, called Port Vallais, (Portus Valesise of the Romans,) once situated at the water's edge, at the upper end, is now more than a mile and a half inland, this intervening alluvial tract having been De la Beche, Ed, Phil. Journ., vol. ii. p. 107, Jan. 1820. 254 DELTA OF THE RHONE [Ch. acquired in about eight centuries. The remainder of the delta consists of a flat alluvial plain, about five or six miles in length, composed of sand and mud, a little raised above the level of the river and full of marshes. Mr. De la Beche found, after numerous soundings in all parts of the lake, that there was a pretty uniform depth of from one hundred and twenty to one hundred and sixty fathoms throughout the central region, and, on approaching the delta, the shallowing of the bottom began to be very sensible at a distance of about a mile and three-quarters from the mouth of the Rhone ; for a line drawn from St. Gingoulph to Vevey, jives a mean depth of somewhat less than six hundred feet, and from that part to the Rhone, the fluviatile mud is always found along the bottom *. We may state, therefore, that the strata annually produced are about two miles in length : so that, notwithstanding the great depth of the lake, the new deposits are not inclined at a high angle ; the dip of the beds, indeed, is so slight, that they would be termed, in ordinary geological language, horizontal. The strata probably consist of alternations of finer and coarser particles, for, during the hotter months from April to August, when the snows melt, the volume and velocity of the river are greatest, and large quantities of sand, mud, vegetable matter, and drift-wood are introduced ; but, during the rest of the year, the influx is comparatively feeble, so much so, that the whole lake, according to Saussure, stands six feet lower. If, then, we could obtain a section of the accumulation formed in the last eight centuries, we should see a great series of strata, probably from six to nine hundred feet thick, and nearly two miles in length, inclined at a very slight angle. In the mean time, a great number of smaller deltas are growing around the borders of the lake, at the mouths of rapid torrents, which pour in large masses of sand and pebbles. The body of water in these torrents is too small to enable them to spread out the transported matter over so extensive an area as the Rhone. - * De la Beche, MS. Ch. XIII.] JN THE LAKE OF GENEVA. 255 Thus, for example, there is a depth of eighty fathoms within half a mile of the shore, immediately opposite the great tor- rent which enters east of Ripaille, so that the dip of the strata in that delta is about four times as great as those deposited by the main river at the upper extremity of the lake*. Chronological computations of the age of deltas. The capa- city of this basin being now ascertained, it would be an inte- resting subject of inquiry, to determine in what number of years the Leman Lake will be converted into dry land. It would not be very difficult to obtain the elements for such a calculation, so as to approximate at least to the quantity of time required for the accomplishment of this result. The num- ber of cubic feet of water annually discharged by the river into the lake being estimated, experiments might be made in the winter and summer months, to determine the proportion of matter held in suspension or in chemical solution by the Rhone. It would be also necessary to allow for the heavier matter drifted along at the bottom, which might be estimated on hydrostatical principles, when the average size of the gravel and the volume and velocity of the stream at different seasons were known. Supposing all these observations to have been made, it would be more easy to calculate the future than the former progress of the delta, because it would be a laborious task to ascertain, with any degree of precision, the original depth and extent of that part of the lake which is already filled up. Even if this information were actually obtained by borings, it would only enable us to approximate within a cer- tain number of centuries to the time when the Rhone began to form its present delta ; but this would not give us the date of the origin of the Leman Lake in its present form, because the river may have flowed into it for thousands of years, with- out importing any sediment whatever. Such would have been the case, if the waters had first passed through a chain of upper lakes ; and that this was actually the fact, is indicated by the course of the Rhone between Martigny and the Lake * De la Becbe, MS. 25S CHRONOLOGICAL COMPUTATIONS OF [Ch. XIII* of Geneva, and still more decidedly, by the channels of many of its principal feeders. If we ascend, for example, the valley through which the Dranse flows, we find that it consists of a succession of basins, one above the other, in each of which there is a wide expanse of flat alluvial lands, separated from the next basin by a rocky gorge, once evidently the barrier of a lake. The river has filled the lake, and partially cut through the barrier, which it is still gradually eroding to a greater depth. The examination of almost all valleys in mountainous districts affords abundant proofs of the obliteration of a series of lakes, by the filling up of hollows and the cutting through of rocky barriers a process by which running water ever labours to produce a more uniform declivity. Before, therefore, we can pretend even to hazard a conjecture as to the era at which any particular delta com- menced, we must be thoroughly acquainted with the geologica. history of the whole system of higher valleys which communi- cate with the main stream, and all the changes which they have undergone since the last series of convulsions which agitated and altered the face of the country. The probability, therefore, of error in our chronological computations, where we omit to pay due attention to these cir- cumstances, increases in proportion to the time that may have elapsed since the last disturbance of the country by subterra- nean movements, and in proportion to the extent of the hydro- graphical basin on which we may happen to speculate. The Alpine rivers of Vallais are prevented at present from con- tributing their sedimentary contingent to the delta of the Rhone in the Mediterranean, because they are intercepted by the LemanLake; but when this is filled, they will transport as much, or nearly as much, matter to the sea as they now pour into that lake. They will then flow through a long, flat, allu- vial plain, between Villeneuve and Geneva, from two to eight miles in breadth, which will present no superficial marks of the existence of a thickness of more than one thousand feet of recent sediment below. Many hundred alluvial tracts of equal, Ch. XIII.] "THE AGE OF DELTAS. 257 and some of much greater area, may be seen if we follow up the Rhone from its mouth, or explore the valleys of many of its principal tributaries. What, then, shall we think of the presumption of De Luc, Kirwan, and their followers, who confidently deduced from the phenomena of modern deltas the recent origin of the present form of our continents, without pretending to have collected any one of the numerous data by which so complicated a pro- blem can be solved ? Had they, after making all the necessary investigations, succeeded in proving, as they desired, that the delta of the Rhone, and the new deposits at the mouths of all other rivers, whether in lakes or seas, had required about four thousand years to attain their present dimensions, the conclu- sion would have been fatal to the chronological theories, which they were anxious to confirm. The popular reception of these, and similar sophisms, respecting the effects of causes in diurnal action has hitherto thrown stumbling-blocks in the way of those geologists who desire to pursue the science according to the rules of inductive philosophy. If speculations so vague and visionary can be proposed concerning natural operations now passing before our eyes if authors may thus dogmatize, with impunity, on subjects capable of being determined with a considerable degree of precision, can we be surprised that they who reason on the more obscure phenomena of remote ages, should wander in a maze of error and inconsistency ? The Leman Lake fills a great cavity in rocky strata, com- posed of a tertiary conglomerate and sand, which constitutes its bottom, almost all its northern banks, and a great part of its southern or Alpine side. It has often been asked, why this cavity has not been filled up by the detritus of rocks, removed from the numerous valleys now drained by the waters which enter the lake ? In order to remove this difficulty, it would be necessary to enter into a description of the strata of different ages composing the Alps and the Subalpine districts ; to point out the distinct periods of their elevation above the sea, and the pre-existence of many mountain valleys, even to the for- VOL. I. S 258 DELTAS OF LA.KE SUPERIOR. [Ch. XIII. mation of those deposits wherein the Lake of Geneva is con- tained. It would be premature, therefore, to enter upon this subject at present, to which we shall revert when we have de- scribed the phenomena of some of the ancient strata. Lake Superior. Lake Superior is the largest body of fresh water in the world, being about one thousand five hundred geographical miles in circumference, if we follow the sinuosities of its coasts, its length, on a curved line through its centre, being about three hundred and sixty, and its extreme breadth one hundred and forty geographical miles. Its average depth varies from eighty to one hundred and fifty fathoms ; but, ac- cording to Captain Bayfield, there is reason to think that its greatest depth would not be overrated at two hundred fathoms *, so that its bottom is, in some parts, nearly six hundred feet below the level of the Atlantic, as its surface is about as much above it. There are appearances in different parts of this, as of the other Canadian lakes, leading us to infer that its waters have formerly occupied a much higher level than they reach at present ; for at a considerable distance from the present shores, parallel lines of rolled stones and shells are seen rising one above the other, like the seats of an amphitheatre. These ancient lines of shingle are exactly similar to the present beaches in most bays, and they often attain an elevation of forty or fifty feet above the present level. As the heaviest gales of wind do not raise the waters more than three or four feetf, the elevated beaches must either be referred to the subsidence of the lake at former periods, in con- sequence of the wearing down of its barrier, or to the upraising of the shores by earthquakes, like those which have produced similar phenomena on the coast of Chili. But there seem, to be no facts which lend countenance to the latter hypothesis, in * Trans, of Lit. and Hist. Soc. of Quebec, vol. i. p. 5, 1829. f Captain Bayfield remarks, that Dr. Bigsby, to whom we are indebted for seve- ral communications respecting the geology of the Canadian lakes, was misinformed by the fur traders in regard to the extraordinary height (twenty or thirty feet) to which he asserts that the autumnal gales will raise the water of Lake Superior. Ibid., p. 7. Ch. XIII.] DELTAS OF THE BALTIC. 259 reference to the North American lakes. The streams which discharge their waters into Lake Superior are several hundred in number, without reckoning those of smaller size ; and the quantity of water supplied by them is many times greater than that discharged at the Falls of St. Mary, the only outlet. The evaporation, therefore, is very great, and such as might be ex- pected from so vast an extent of surface. On the northern side, which is encircled by primary moun- tains, the rivers sweep in many large boulders with smaller gravel and sand, chiefly composed of granitic and trap rocks. There are also currents in the lake, in various directions, caused by the continued prevalence of strong winds, and to their influ- ence we may attribute the diffusion of finer mud far and wide over great areas ; for, by numerous soundings made during the late survey, it was ascertained that the bottom consists gene- rally of a very adhesive clay, containing shells of the species at present existing in the lake. When exposed to the air, this clay immediately becomes indurated in so great a degree, as to require a smart blow to break it. It effervesces slightly with diluted nitric acid, and is of different colours in different parts of the lake ; in one district blue, in another red, and in a third white, hardening into a substance resembling pipe-clay *. From these statements, the geologist will not fail to remark how closely these recent lacustrine formations in America resemble the tertiary argillaceous and calcareous marls of lacustrine origin in Central France. In both cases, many of the genera of shells most abundant^ as Lymnea and Planorbis, are the same ; and in regard to other classes of organic remains, there must be the closest analogy, as we shall endeavour more fully to explain when speaking of the imbedding of plants and ani- mals in recent deposits. DELTAS OF INLAND SEAS. Supposed diminution of level in the Baltic. Having offered * Trans, of Lit, and Hist. Soc. of Quebec, vol. i, p. 5, 1829. S2 2GO SUPPOSED DIMINUTION OF [Ch. XIII. these few remarks on lacustrine deltas now in progress, we may next turn our attention to those of inland seas. The shallowing and conversion into land of many parts of the Baltic, especially the Gulfs of Bothnia and Finland, have been demonstrated by a series of accurate observations, for which we are in a great measure indebted to the animated con- troversy which has been kept up, since the middle of the last century, concerning the gradual lowering of the level of the Baltic. Celsius, the Swedish astronomer, first originated the idea, that from the earliest times there had been a progressive fall of about forty-five inches in a century, in the mean level of the waters of that sea. He contended that this change rested not only on modern observations, but on the authority of the ancient geographers, who stated that Scandinavia was for- merly an island. By the gradual depression of the sea, he said, that great island became connected with the continent ; and that this event happened after the time of Pliny, and before the ninth century of our era. To the arguments urged in support of these positions, his opponents objected that the ancients were so ignorant of the geography of the most northern parts of Europe, that their authority was entitled to no weight ; and that their represen- tation of Scandinavia as an island, might with more propriety be adduced to prove the scantiness of their information, than to confirm so bold an hypothesis. It was also remarked that if the land which connected Scandinavia with the main continent was laid dry between the time of Pliny and the ninth century, to the extent to which it is known to have risen above the sea at the latter period, the rate of depression could not have been uniform, as was pretended, for it ought to have fallen much more rapidly between the ninth and eighteenth century. Many of the physical proofs relied on by Celsius and his followers show clearly that they did not distinguish between the shallowing of the water by deposition of fresh sediment, and the diminution of depth caused by subsidence of the sea. By their own statements, it appeared that the accessions of new Ch. XIII.] THE LEVEL OF THE BALTIC. 261 land, and the loss of depth^ were at the mouths of rivers,, or in certain deep bays, into which it is well known that sand and mud are carried by currents. As illustrating, however, the gradual conversion of the Gulf of Bothnia into land, their ob- servations deserve great attention. Thus, for example, they pointed out the fact, that at Pitea half a mile was gained in forty-five years, and at Lulea no less than a mile in twenty- eight years. Ancient ports on the same coast had become inland cities. Considerable tracts of the gulf were rendered three feet shallower in the course of fifty years many old fishing-grounds had been changed into dry land small islands had been joined to the continent. According to Linnaeus, the increase of land on the eastern side of Gothland, near Hoburg, was about two or three toises annually for ninety years*. Besides these changes, it was asserted that, along the south- ern shore also of the Baltic, particularly in West Prussia and Pomerania, anchors and sunk ships had been discovered far inland ; and although these occurrences were partly accounted for by the silting up of river-beds, yet the tradition seems worthy of credit, that a bay of the sea penetrated, at a remote period, much farther to the south in that direction. These, and many other facts, are of geological interest, although they afford no confirmation to the theory of Celsius. His most plausible arguments were derived from the alleged exposure of certain insular rocks in the Bothnian and other bays, which were declared to have been once entirely covered with water, but which had gradually protruded themselves more and more above the waves, until, in the course of about a century and a half, they grew to be eight feet high. Of this phenomenon the following explanation was offered by his opponents. The islands in question consisted of sand and drift-stones, and the waves, during great tempests, threw up new matter upon them, or converted shoals into islands. Sometimes, also, icebergs, heavily laden with rock, were * Linn, de tell* habit, increm. 262 SUPPOSED DIMINUTION OF [Ch, XIII, stranded on a shoal or driven up on a low island ; and when they melted away, they left a mass of debris, many feet in height. Browallius, and other Swedish naturalists, pointed out that some of these islands were lower than formerly ; so that, by reference to this kind of evidence, there was equally good rea- son for contending that the level of the Baltic was gradually rising. They also added another curious and very conclusive proof of the permanency of the water-level for many centuries. On the Finland coast were some large pines, growing close to the water's edge; these were cut down, and, by counting the concentric rings of annual growth, as seen in a transverse sec- tion of the trunk, it was demonstrated that they had stood there for four hundred years. Now, according to the Celsian hypothesis, the sea had sunk fifteen feet during that period, so that the germination and early growth of these pines must have been for many seasons below the level of the water. In like manner it was shown, that the lower walls of many ancient castles, such as those of Sonderburg and Abo, reached then to the water's edge, and must, therefore, according to the theory of Celsius, have been originally constructed below the level of the sea. Another unanswerable argument in proof of the stability of the level of the Baltic was drawn from the island of Saltholm, not far from Copenhagen. This isle is so low that, in autumn and winter, it is permanently overflowed ; and it is only dry in summer, when it serves for pasturing cattle. It appears, from documents of the year 1280, that this island was then also in the same state, and exactly on a level with the mean height of the sea, instead of being twenty feet under water, as it ought to have been according to the computation of Celsius. Several towns, also, on the shores of the Baltic, as Lubeck, Wismar, Rostock, Stralsund, and others, after six and even eight hun- dred years, are as little elevated above the sea as at the era of their foundation, being now close to the water's edge. The lowest part of Dantzic was no higher than the mean level of Ch. XIIL] THE LEVEL OF THE BALTIC. 263 the sea in the year 1000 ; and after eight centuries its relative position remains exactly the same *. Notwithstanding these convincing proofs that the supposed change in the relative level of land and sea arose from some local appearances, there are still many who contend for a low- ering of the Baltic ; and many Swedish officers of the pilotage establishment declared, in the year 1821, in favour of this opi- nion, after measuring the height of landmarks placed at certain heights above the sea half a century before, as objects of com- parison, for the express purpose of settling the point at issue. Before we attach any weight to these assertions, which only relate to slight differences of elevation, we ought to be assured that the observers were on their guard against every imagin- able cause of deception arising from local circumstances. Thus, for example, if the height of an alluvial plain was taken during the last century, it might have been subsequently raised by fresh deposits, and thus the sea would appear to have sunk ; or, if a mark was cut in the rocks, the sea may have been seve- ral inches or even feet higher at one period than another, in consequence of the setting in of a current urged by particular winds into a long narrow gulf, which cause is well known to raise the Baltic, at some seasons, two feet above its ordinary level. It is however possible that this inland sea, filled as it is with river-water, and, unlike the Mediterranean, discharging into the ocean more water than it receives from it, may resemble the estuary of a great river, rising many feet above the mean level of the ocean. In this case, the Baltic may have gradually lowered its level during several successive centuries, in propor- tion as it obtained a freer efflux, occasioned by the widening of the channel of discharge during encroachments of the German ocean. Elevated beaches in Sweden. Von Buch, in his travels, dis- covered in Norway, and at Uddevalla in Sweden, beds of shells * For a full account of the Celsian controversy, we may refer our readers to Von Hoff, Geschichte, &c. ; vol. i. p. 439. 264 SUPPOSED DIMINUTION OF [Ch. XIII. of existing species at considerable heights above the level of the water. Since that time, several other naturalists have con- firmed his observation ; and, according to Strom, some deposits occur at an elevation of more than four hundred feet above the sea in the northern part of Norway. M. Alex. Brongniart, who has lately visited Uddevalla in Gotheborg, a port at the entrance of the Baltic, informs us that the principal mass of shells in the creek of Uddevalla rises about two hundred feet above the level of the sea, resting on rocks of gneiss. All the species are identical with those now inhabiting the contiguous sea, and are for the most part entire, although some of them are broken, as happens on a sea-beach. They are nearly free from any admixture of earthy matter. The reader need scarcely be reminded that, at the height of a few feet above the beach, on our coasts, the rocks, where they are alternately submerged and laid dry by the ebbing and flowing tide, are frequently covered with barnacles or balani, which are firmly attached. On examining with care the smooth surface of the gneiss, im- mediately above the ancient shelly beach at Uddevalla, M. Brongniart found, in a similar manner, balani adhering to the rocks, so that there can be no doubt that the sea had for a long period sojourned on the spot*. Now, this interesting fact is precisely analogous to one well known to all who are acquainted with the geology of the bor- ders of the Mediterranean. Perforating testacea of the genus Lithodomus, Cuv., excavate funnel-shaped hollows in the hardest limestone and marble, along the present sea-shores; and lines of these perforations, sometimes containing the same species of shells, have been discovered at various heights above the sea near Naples, in Calabria, at Monte Pelegrino, in the Bay of Palermo, and other localities. As many of these districts have been violently shaken by earthquakes within the historical era, and as the land has been sometimes raised and sometimes depressed, as we shall afterwards show by examples, there is no difficulty in explaining the pheno- * Tableau des Terrains, &c., p. 89. 1829. Ch. XIII.] THE LEVEL OF THE BALTIC. 265 mena, provided time be allowed. But no argument can be derived, from such observations, in support of great upheavings of the coast, whether by slow or sudden operations in modern times, unless we use the term modern in a geological sense. On the contrary, we know that the physical outline of the coast and heights in the bay of Palermo, when it was a Greek port, more than two thousand years ago, was so nearly the same as it is at present, that the beds of recent shells, and the perfora- tions in the rocks, must have stood nearly in the same relation to the level of the Mediterranean as they stand now, The high beaches on the Norwegian and Swedish coast esta- blish the important and certainly very unexpected fact, that those parts of Europe have been the theatres of considerable subterranean movements within the present zoological era, or since the seas were inhabited by species now our contemporaries. But the phenomena do not lend the slightest support to the Cel- sian hypothesis, nor to that extraordinary notion proposed in our own times by Von Buch, who imagines that the whole of the land along the northern and western shores of the Baltic is slowly and insensibly rising! No countries have been more en- tirely free from earthquakes since the times of authentic his- tory than Norway, Sweden, and Denmark. In common with our own island, and, indeed, with almost every spot on the globe, they have experienced some slight shocks at certain periods, as during the earthquake of Lisbon, and on a few other occasions, but these may rather be considered as pro- longed vibrations in the crust of the earth, extending in the manner of sounds through the air to almost indefinite dis- tances, than as those violent movements which in the great regions of active volcanos change, from time to time, the rela- tive level of the land and sea. Delta of the Rhone. We may now turn our attention to some of the principal deltas of the Mediterranean, for no other inland sea affords so many examples of accessions of new lands at the mouths of rivers within the records of authentic history. We have already considered the lacustrine delta of the Rhone 266 DELTA OF THE RHONE. [Ch, XIII. in Switzerland, and we shall now describe its contemporaneous marine delta. Scarcely has the river passed out of the Leman Lake, before its pure waters are again filled with sand and sediment by the impetuous Arve, descending from the highest Alps, and bearing along in its current the granitic detritus annually carried down by the glaciers of Mont Blanc. The Rhone afterwards receives vast contributions of transported matter from the Alps of Dauphiny, and the primary and vol- canic mountains of Central France ; and when at length it enters the Mediterranean, it discolours its blue waters with a whitish sediment for the distance of between six and seven miles from its mouth, throughout which space the current of fresh- water- is perceptible. Proofs of its increase since historical period. Strabo's de- scription of the delta is so inapplicable to its present configu- ration, as to attest a complete alteration in the physical features of the country since the Augustan age. It appears, however, that the head of the delta, or the point at which it begins to ramify, has remained unaltered since the time of Pliny, for he states that the Rhone divided itself at Aries into two arms. This is the case at present ; one of the branches being now now called Le petit Rhone, which is again subdivided before entering the Mediterranean. The advance of the base of the delta, in the last eighteen centuries, is demonstrated by many curious antiquarian monuments. The most striking of these is the great detour made by the old Roman road from Uger- num to Beziers (part of the high road between Aix, Aquae Sextiae, and Nismes, Nemausus). It is clear that, when this was first constructed, it was impossible to pass in a direct line, as now, across the delta, and that either the sea or marshes intervened in a tract now consisting of terra firma *. Astruc also remarks, that all the places on the low lands, lying to the north of the old Roman road between Nismes and Beziers, have names of Celtic origin evidently given to them by the first in- habitants of the country ; whereas the places lying south of * Mem, d' Astruc, cited by Von Hoff, vol. i. p. 228. Ch.XIII.] DELTA OF THE RHONE. 267 that road, towards the sea, have names of Latin derivation, and were clearly founded after the Roman language had been introduced. Another proof, also, of the great extent of land which has come into existence since the Romans conquered and colonized Gaul, is derived from the fact, that the Roman writers never mention the thermal waters of Balaruc in the delta, although they were well acquainted with those of Aix and others, still more distant, and attached great importance to them, as they invariably did to all hot.springs. The waters of Balaruc, therefore, must have formerly issued under the sea a common phenomenon on the borders of the Mediterranean ; and on the advance of the delta they continued to flow out through the new deposits. Among the more direct proofs of the increase of land, we find that Mese, described under the appellation of Mesua Collis by Pomponius Mela*, and stated by him to be nearly an island, is now far inland. Notre Dame des Ports, also, was a harbour in 898, but is now a league from the shore. Psalmodi was an island in 815, and is now two leagues from the sea. Several old lines of towers and sea-marks occur at different distances from the present coast, all indicating the successive retreat of the sea, for each line has in its turn become useless to mariners, which may well be conceived, when we state that the tower of Tignaux, erected on the shore so late as the year 1737, is already a French mile remote from it f. By the confluence of the Rhone and the currents of the Mediterranean driven by winds from the south, sand-bars are often formed across the mouths of the river: by these means considerable spaces become divided off from the sea, and sub- sequently from the river also, when it shifts its channels of efflux. As some of these lagoons are subject to the occasional ingress of the river when flooded, and of the sea during storms, they are alternately salt and fresh. Others, after being filled * Lib. ii., c . v. f Bouche, Chorographie et Hist, de Provence, vol. i. p. 23, cited by Hoff, vol. i. p. 290. 268 DELTA OF THE RHONE. [Ch. XIII. with salt- water, are often lowered by evaporation till they be- come more salt than the sea ; and it has happened, occasion- ally, that a considerable precipitate of muriate of soda has taken place in these natural salterns. During the latter part of Napoleon's career, when the excise-laws were enforced with extreme rigour, the police was employed to prevent such salt from being used. The fluviatile and marine shells enclosed in these small lakes often live together in brackish water ; but the uncongenial nature of the fluid usually produces a dwarfish size, and sometimes gives rise to strange varieties in form and colour. Captain Smyth, in the late survey of the coast of the Medi- terranean, found the sea, opposite the mouth of the Rhone, to deepen gradually from four to forty fathoms, within a dis- tance of six or seven miles, over which the discoloured fresh water extends; so that the inclination of the new deposits must be too slight to be appreciable in such an extent of section as a geologist usually obtains in examining ancient formations. When the wind blew from the south-west, the ships employed in the survey were obliged to quit their moorings ; and when they returned, the new sand-banks in the delta were found covered over with a great abundance of marine shells. By this means, we learn how occasional beds of drifted marine shells may become interstratified with fresh- water strata at the mouths of rivers. Stony nature of its deposits. That a great proportion, at least, of the new deposit in the delta of the Rhone consists of rock, and not of loose incoherent matter, is perfectly ascer- tained. In the Museum at Montpellier is a cannon taken up from the sea near the mouth of the river, imbedded in a crys- talline calcareous rock. Large masses, also, are continually taken up of an arenaceous rock, cemented by calcareous matter, including multitudes of broken shells of recent species. The observations recently made on this subject corroborate the for- mer statement of Marsilli*, that the earthy deposits of the * Hist. Phys. de la Her. Ch. XIII.] DELTA OF THE PO. 269 coast of Languedoc form a stony substance, for which reason he ascribed a certain bituminous, saline, and glutinous nature to the substances brought down with sand by the Rhone. If the number of mineral springs charged with carbonate of lime which fall into the Rhone and its feeders in different parts of France be considered, we shall feel no surprise at the lapidification of the newly-deposited sediment in this delta. It should be remembered that the fresh water intro- duced by rivers, being lighter than the water of the sea, floats over the latter, and remains upon the surface for a considerable distance. Consequently, it is exposed to as much evaporation as the waters of a lake ; and the area over which the river- water is spread, at the junction of great rivers and the sea, may well be compared, in point of extent, to that of considerable lakes. Now, it is well known, that so great is the quantity of water carried off by evaporation in some lakes, that it is nearly equal to the water flowing in ; and in some inland seas, as the Caspian, it is quite equal. We may, therefore, well suppose that, in cases where a strong current does not interfere, the greater portion not only of the matter held mechanically in suspension, but of that also which is in chemical solution, must be precipitated within the limits of the delta. When these finer ingredients are extremely small in quantity, they may only suffice to supply crustaceous animals, corals, and marine plants, with the earthy particles necessary for their secretions ; but whenever it is in excess (as generally happens if the basin of a river lie partly in a district of active or extinct volcanos) , then will solid deposits be formed, and the shells will at once be included in a rocky mass. Delta of the Po. The Adriatic presents a great combina- tion of circumstances favourable to the rapid formation of deltas a gulf receding far into the land, a sea without tides or strong currents, and the influx of two great rivers, the Po and the Adige, besides numerous minor streams draining on the one side a great crescent of the Alps, and on the other 270 DELTA OF THE PO. [Ch. XIII. some of the loftiest ridges of the Apennines. From the northernmost point of the Gulf of Trieste, where the Isonzo enters, down to the south of Ravenna, there is an uninterrupted series of recent accessions of land, more than one hundred miles in length, which, within the last two thousand years, have increased from two to twenty miles in breadth. The Isonzo, Tagliamento, Piave, Brenta, Adige, and Po, besides many other inferior rivers, contribute to the advance of the coast-line, and to the shallowing of the gulf. The Po and the Adige may now be considered as entering by one common delta, for two branches of the Adige are connected with arms of the Po. In consequence of the great concentration of the flooded waters of these streams, since the system of embankment became general, the rate of encroachment of the new land upon the Adriatic, especially at that point where the Po and Adige enter, is said to have been greatly accelerated. Adria was a seaport in the time of Augustus, and had, in ancient times, given its name to the gulf; it is now about twenty Italian miles inland. Ravenna was also a seaport, and is now about four Italian miles from the main sea. Yet even before the practice of embankment was introduced, the allu- vium of the Po advanced with rapidity on the Adriatic ; for Spina, a very ancient city, originally built in the district of Ravenna, at the mouth of a great arm of the Po, was, so early as the commencement of our era, eleven Italian miles distant from the sea *. The greatest depth of the Adriatic, between Dalmatia and the mouths of the Po, is twenty-two fathoms ; but a large part of the gulf of Trieste and the Adriatic, opposite Venice, is less than twelve fathoms deep. Farther to the south, where it is less affected by the influx of great rivers, the gulf deepens considerably. Donati, after dredging the bottom, discovered the new deposits to consist partly of mud and partly of rock, " See Brocchi on the various writers on this subject. Conch, Foss, Subap.. vol. i, p. 118. DELTA OF THE PO. 271 the latter formed of calcareous matter, encrusting shells. He also ascertained, that particular species of testacea were grouped together in certain places, and were becoming slowly incorpo- rated with the mud, or calcareous precipitates*. Olivi, also, found some deposits of sand, and others of mud, extending half way across the gulf ; and he states that their distribution along the bottom was evidently determined by the prevailing current f. It is probable, therefore, that the finer sediment of all the rivers at the head of the Adriatic may be intermingled by the influence of the current ; and all the central parts of the gulf may be considered as slowly filling up with horizontal deposits, precisely similar to those of the Subapennine hills, and containing many of the same species of shells. The Po merely introduces at present fine sand and mud, for it carries no pebbles farther than the spot where it joins the Trebia, west of Piacenza. Near the northern borders of the basin, the Isonzo, Tagliamento, and many other streams, are forming immense beds of sand and some conglomerate, for there some high mountains of Alpine limestone approach within a few miles of the sea. In the time of the Romans, the hot-baths of Monfalcone were on one of several islands of Alpine limestone, between which and the main land, on the north, was a channel of the sea, about a mile broad. This channel is now converted into a grassy plain, which surrounds the islands on all sides. Among the numerous changes on this coast, we find that the present channel of the Isonzo is several miles to the west of its ancient bed, in part of which, at Ronchi, the old Roman bridge which crossed the Via Appia was lately found buried in fluvia- tile silt. Notwithstanding the present shallowness of the Adriatic, it is highly probable that its original depth was very great ; for if all the low alluvial tracts were taken away from its borders and replaced by sea, the high land would terminate in that * See Brocchi on the various writers on this subject. Conch. Foss. Subap., vol. i. p. 39. t Ibid., vol. ii. p. 94, 272 DELTA OF THE NILE. [Ch. XIIT. abrupt manner which generally indicates, in the Mediterranean, a great depth of water near the shore, except in those spots where sediment imported by rivers and currents has diminished the depth. Many parts of the Mediterranean are now ascer- tained to be above two thousand feet deep, close to the shore, as between Nice and Genoa ; and even sometimes six thousand feet, as near Gibraltar. When, therefore,, we find near Parma, and in other districts in the interior of the peninsula, beds of horizontal tertiary marl, attaining a thickness of about two thousand feet, or when we discover strata of inclined conglome- rate, of the same age, near Nice, measuring above a thousand feet in thickness, and extending seven or eight miles in length, we behold nothing which the analogy of the deltas in the Adriatic might not lead us to anticipate. Delta of the Nile. That Egypt was the gift of the Nile, was the opinion of her priests before the time of Herodotus ; but we have no authentic memorials for determining, with accuracy, the additions made to the habitable surface of that country since the earliest historical period. We know that the base of the delta has been considerably modified since the days of Homer. The ancient geographers mention seven principal mouths of the Nile, of which the most eastern, the Pelusian, has been entirely silted up, and the Mendesian, or Tanitic, has disappeared. On the other hand, the Bucolic has, in modern timesj been greatly enlarged, and has caused the coast to ad- vance; so that the city of Damietta, which, in the year 1243, was on the sea s and possessed a good harbour, is now one mile inland. The Phatnitic mouth, and the Sebenitic, have been so altered, that the country immediately about them has little resemblance to that described by the ancients. The Bolbitine mouth has increased in its dimensions, so as to cause the city of Rosetta to be at some distance from the sea. But the alterations produced round the Canopic mouth are the most important. The city Foah, which, so late as the be- ginning of the fifteenth century, was on this embouchure, is now more than a mile inland. Canopus, which, in the time of Ch. XIII.] DELTA OF THE NILE. 273 Scylax, was a desolate insular rock, has been connected with the firm land ; and Pharos, an island in the times of old, now belongs to the continent. Homer says, its distance from Egypt was one day's voyage by sea *. That this should have been the case in Homer's time, Larcher and others have, with rea- son, affirmed to be in the highest degree improbable; but Strabo has judiciously anticipated their objections, observing, that Homer was probably acquainted with the gradual advance of the land on this coast, and availed himself of this pheno- menon to give an air of higher antiquity to the remote period in which he laid the scene of his poem f. The Lake Mareotis, also, together with the canal which connected it with the Ca- nopic arm of the Nile, has been filled with mud, and is become dry. Herodotus observes, that the country round Memphis seemed formerly to have been an arm of the sea gradually filled by the Nile, in the same manner as the Meander, Achelous, and other streams, had formed deltas. ' Egypt, therefore,' he says, * like the Red Sea, was once a long narrow bay, and both gulfs were separated by a small neck of land. If the Nile,' he adds, ' should by any means have an issue into the Arabian Gulf, it might choke it up with earth in twenty thousand, or even, perhaps, in ten thousand years ; and why may not the Nile have filled with mud a still greater gulf, in the space of time which has passed before our age J ? ' Mud of the Nile. The analysis of the mud of the Nile gives nearly one-half of argillaceous earth, and about one-fourth of carbonate of lime, the remainder consisting of water, oxide of iron, and carbonate of magnesia . The depth of the Mediterranean is about twelve fathoms at a small distance from the shore of the delta ; it afterwards in- creases gradually to fifty, and then suddenly descends to three hundred and eighty fathoms, which is, perhaps, the original * Ody., book iv. p. 355. f Lib. I., Part i. pp. 80 and 98. Consult Von Hoff, vol. i. p. 244. J Euterpe, XI. Girard, Mem. sur PEgypte, tome i. pp. 348 .382. VOL. I. T 274 DELTA OF THE NILE. [Ch. XIII. depth of the sea where it has not been rendered shallower by fluviatile matter. The progress of the delta, in the last two thousand years, affords, perhaps, no measure for estimating its rate of growth when it was an inland bay, and had not yet pro- truded itself beyond the coast-line of the Mediterranean. A powerful current now sweeps along the shores of Africa, from the Straits of Gibraltar to the prominent convexity of Egypt, the western side of which is continually the prey of the waves ; so that not only are fresh accessions of land checked, but ancient parts of the delta are carried away. By this cause Canopus, and some other towns, have been overwhelmed ; but to this subject we shall again refer when speaking of tides and cur- rents. CHAPTER XIV. ;anic deltas Delta of the Ganges and Burrampooter Its size, rate of advance, and nature of its deposits Formation and destruction of islands Abundance of crocodiles Inundations Delta of the Mississippi Deposits of drift wood Gradual filling up of the Yellow Sea Rennell's estimate of the mud carried down by the Ganges Formation of valleys illustrated by the growth of deltas Grouping of new strata in general Convergence of deltas Conglomerates -Various causes of stratification Direction of laminae Remarks on the inter- of land and sea. OCEANIC DELTAS. THE remaining class of deltas are those in which rivers, on en- tering the sea, are exposed to the influence of the tides. In this case it frequently happens that an estuary is produced, or negative delta, as it has been termed by Rennell, where, instead of any encroachment of the land upon the sea, the ocean enters the river's mouth, and penetrates into the land beyond the general coast-line. Where this happens, the tides and currents are the predominating agents in the distribution of transported sediment. The phenomena, therefore, of such estuaries, will come under our examination when we treat of the movements of the ocean. But whenever the volume of fresh water is so great as to counteract and almost neutralize the force of tides and currents, and in all cases where the latter agents have not sufficient power to remove to a distance the whole of the sediment periodically brought down by rivers, oceanic deltas are produced. Of these, we shall now select a few illustrative examples. Delta of the Ganges. The Ganges and the Burrampooter descend, from the highest mountains in the world, into a gulf which runs two hundred and twenty-five miles into the conti- nent. The Burrampooter is somewhat the larger river of the two, but it first takes the name of the Megna, when joined by a T2 276 DELTA OF THE GANGES. [Ch. XIV. smaller stream so called, and afterwards loses this second name also on its union with the Ganges, at the distance of about forty miles from the sea. The area of the delta of the Ganges (without including that of the Burrampooter, which has now become conterminous) is considerably more than double that of the Nile ; and its head commences at a distance of two hun- dred and twenty miles, in a direct line from the sea. That part of the delta bordering on the sea is composed of a laby- rinth of rivers and creeks, all of which are salt, except those immediately communicating with the principal arm of the Ganges. This tract, known by the name of the Woods, or Sunderbunds, a wilderness infested by tigers and alligators, is, according to Rennell, equal in extent to the whole principality of Wales *. The base of this magnificent delta is two hundred miles in length, including the space occupied by the two great arms of the Ganges which bound it on either side. On the sea-coast there are eight great openings, each of which has evidently, at some ancient period, served in its turn as the principal channel of discharge. Although the flux and reflux of the tide extend even to the head of the delta, when the river is low, yet, when it is periodically swollen by tropical rains, the velocity of the stream counteracts the tidal current, so that, except very near the sea, the ebb and flow become insensible. During the flood season, therefore, the Ganges almost assumes the character of a river entering a lake or in- land sea ; the movements of the ocean being then subordinate to the force of the river, and only slightly disturbing its opera- tions. The great gain of the delta in height and area takes place during the inundations ; and during other seasons of the year, the ocean makes reprisals, scouring out the channels, and sometimes devouring rich alluvial plains. So great is the quantity of mud and sand poured by the Ganges into the gulf in the flood-season, that the sea only re- covers its transparency at the distance of sixty miles from the * Account of the Ganges and Burrampooter Rivers, by Major Rennell, Phil, Trans. 1781. Ch. XIV.J DELTA OF THE GANGES. 277 coast. The general slope, therefore, of the new strata must be extremely gradual. By the charts recently published, it ap- pears that there is a gradual deepening from four to about sixty fathoms, as we proceed from the base of the delta to the distance of about one hundred miles into the Bay of Bengal. At some few points seventy, or even one hundred fathoms are obtained at that distance. One remarkable exception, however, occurs to the regularity of the shape of the bottom ; for opposite the middle of the delta, at the distance of thirty or forty miles from the coast, is a nearly circular space called the ' swatch of no ground,' about fifteen miles in diameter, where soundings of one hundred, and even one hundred and thirty fathoms, fail to reach the bottom. This phenomenon is the more extraordinary, since the depression occurs within five miles of the line of shoals ; and not only do the waters charged with Gangetic sediment pass over it con- tinually, but, during the monsoons, the sea, loaded with mud and sand, is beaten back in that direction towards the delta. As the mud is known to extend for eighty miles farther into the gulf, we may be assured that, in the course of ages, the accumulation of strata in c the swatch' has been of enormous thickness ; and we seem entitled to deduce, from the present depth at the spot, that the original inequalities of the bottom of the Bay of Bengal were on as grand a scale as are those of the main ocean. Opposite the mouth of the Hoogly river, and immediately south of Sager Island, four miles from the nearest land of the delta, a new isle was formed about thirty years ago, called Edmonston Island, where there is a lighthouse, and the surface of which is now covered with vegetation and shrubs. But while there is evidence of rapid gain at some points, the general progress of the coast is very slow, for the tides, which rise from thirteen to sixteen feet, are actively employed in removing the alluvial matter, and diffusing it over a wide area *. The new * It is stated in the chart published in the year 1825, by Captain Horsburgh, that the sands opposite the whole delta stretched between four and five miles 278 DELTA OF THE GANGES. [Ch. XIV. strata consist entirely of sand and fine mud ; such, at least, are the only materials which are exposed to view in regular beds on the banks of the numerous creeks. No substance so coarse as gravel occurs in any part of the delta, nor nearer the sea than four hundred miles. It should be observed, however, that the superficial alluvial beds, which are thrown down rapidly from turbid waters during the floods, may be very distinct from those deposited at a greater distance from the shore, where crystalline precipitates, perhaps, are forming, on the evaporation of so great a surface, exposed to the rays of a tropical sun. The separation of sand and other matter, held in mechanical suspension, may take place where the waters are in motion ; but mineral ingredients, held in chemical solution, would naturally be carried to a greater distance, where they aid in the formation of corals and shells, and, in part, perhaps, become the cementing principle of rocky masses. A well was sunk at Fort William, Calcuttta, in the hope of obtaining water through beds of adhesive clay to the depth of one hundred and forty-six feet. A bed of yellow sand was then entered, and at the depth of one hundred and fifty-two feet another stratum of clay*. Islands formed and destroyed. The immense transporta- tion of earthy matter by the Ganges and Megna, is proved by the great magnitude of the islands formed in their channels during a period far short of that of a man's life. Some of these, many miles in extent, have originated in large sand-banks thrown up round the points at the angular turning of the river, and afterwards insulated by breaches of the stream. Others, formed in the main channel, are caused by some obstruction at the bottom. A large tree, or a sunken boat, is sometimes farther south than they had done forty years previously; and this was taken as the measure of the progress of the delta itself, during the same period. But that gentleman informs me that a more careful comparison of the ancient charts, during a recent survey, has proved that they were extremely incorrect in their latitudes, so that the advance of the new sands and delta was greatly exaggerated. * See India Gazette, June 9, 1831. Ch, XIV.] DELTA OF THE GANGES CROCODILES. 279 sufficient to check the current, and cause a deposit of sand, which accumulates till it usurps a considerable portion of the channel. The river then borrows on each side to supply the deficiency in its bed, and the island is afterwards raised by fresh deposits during every flood. In the great gulf below Luckipour, formed by the united waters of the Ganges and Burrampooter (or Megna), some of the islands, says Rennell, rival in size and fertility the Isle of Wight. While the river is forming new islands in one part, it is sweeping away old ones in others. Those newly formed are soon overrun with reeds, long grass, the Tamarix Indica, and other shrubs, form- ing impenetrable thickets, where tigers, buffaloes,, deer, and other wild animals, take shelter. It is easy, therefore, to per- ceive, that both animal and vegetable remains must continually be precipitated into the flood, and sometimes become imbedded in the sediment which subsides in the delta. Two species of crocodiles, of distinct genera, abound in the Ganges and its tributary and contiguous waters; and Mr. H. T. Colebrooke informs me, that he has seen both kinds in places far inland, many hundred miles from the sea. The Gangetic crocodile, or Gavial (in correct orthography, Garial), is confined to the fresh-water, but the common crocodile fre- quents both fresh and salt ; being much larger and fiercer in salt and brackish water. These animals swarm in the brackish water along the line of sand-banks where the advance of the delta is most rapid. Hundreds of them are seen together in the creeks of the delta, or basking in the sun on the shoals without. They will attack men and cattle, destroying the natives when bathing, and tame and wild animals which come to drink. ( I have not unfrequently/ says Mr. Colebrooke, e been witness to the horrid spectacle of seeing a floating corpse seized by a crocodile with such avidity, that he half emerged above the water with his prey in his mouth.' The geologist will not fail to observe how peculiarly the habits and distri- bution of these saurians expose them to become imbedded in those horizontal strata of fine mud which are annually de- 280 DELTA OF THE MISSISSIPPI. [Ch, XIV. posited over many hundred square miles in the Bay of Bengal. The inhabitants of the land, when they happen to be sub- merged, are usually destroyed by these voracious reptiles; but we may suppose the remains of the saurians themselves to be continually entombed in the new formations. Inundations. It sometimes happens, at the season when the periodical flood is at its height, that a strong gale of wind, conspiring with a high spring-tide, checks the descending cur- rent of the river, and gives rise to most destructive inunda- tions. From this cause, in the year 1763, the waters at Luckipour rose six feet above their ordinary level, and the in- habitants of a considerable district, with their houses and cattle, were totally swept away. The population of all oceanic deltas are particularly exposed to suffer by such catastrophes recurring at considerable inter- vals of time ; and we may safely assume, that such tragical events have happened again and again since the Gangetic delta was inhabited by man. If human experience and fore- thought cannot always guard against these calamities, still less can the inferior animals avoid them ; and the monuments of such disastrous inundations must be looked for in great abun- dance in strata of all ages, if the surface of our planet has always been governed by the same laws. When we reflect on the general order and tranquillity that reigns in the rich and populous delta of Bengal, notwithstanding the havoc occasion- ally committed by the depredations of the ocean, we perceive how unnecessary it is to attribute the imbedding of successive races of animals in older strata to extraordinary energy in the causes of decay and reproduction in the infancy of our planet, or to those general catastrophes and sudden revolutions re- sorted to by cosmogonists. Delta of the Mississippi. As the delta of the Ganges may be considered a type of those formed on the borders of the ocean, it will be unnecessary to accumulate examples of others on a no less magnificent scale, as at the mouths of the Orinoco and Amazon, for example. To these, indeed, it will be neces- Ch. XIV.] DELTA OF THE MISSISSIPPI. 281 sary to revert when we treat of the agency of currents. The tides in the Mexican Gulf are so feeble, that the delta of the Mississippi has somewhat of an intermediate character between an oceanic and mediterranean delta. A long narrow tongue of land is protruded, consisting simply of the banks of the river, and having precisely the same appearance as in the inland plains during the periodical inundations, when nothing appears above water but the higher part of that sloping glacis which we before described. This tongue of land has advanced many leagues since New Orleans was built. Great submarine depo- sits are also in progress,, stretching far and wide over the bot- tom of the sea, which has become throughout a considerable area, extremely shallow, not exceeding ten fathoms in depth. Opposite the mouth of the Mississippi large rafts of drift trees, brought down every spring, are matted together into a net- work many yards in thickness, and stretching over hundreds of square leagues*. They afterwards become covered over with a fine mud, on which other layers of trees are deposited the year following, until numerous alternations of earthy and vegetable matter are accumulated. Alternation of Deposits. An observation of Darby, in regard to the strata composing part of this delta, deserves attention. In the steep banks of the Atchafalaya, that arm of the Mississippi which we before alluded to when describing ' the raft,' the following section is observable at low water : first, an upper stratum, consisting invariably of blueish clay, common to the banks of the Mississippi ; below this a stratum of red ochreous earth peculiar to Red River, under which the blue clay of the Mississippi again appears f ; and this arrange- ment is constant, proving, as that geographer remarks, that the waters of the Mississippi and the Red River once occupied alternately considerable tracts below their present point of union. Such alternations are probably common in submarine spaces situated between two converging deltas. For, before the * Captain Hall's Travels in North America, vol. iii. p. 338. f Darby's Louisiana, p. 103. 282 PROPORTION OF SEDIMENT [Ch, XIV. two rivers unite, there must almost always be a certain period when an intermediate tract will be alternately occupied and abandoned by the waters of each stream ; since it can rarely happen that the season of highest flood will precisely corre- spond in each. In the case of the Red River, for example, and Mississippi, which carry off the waters from countries placed under widely distant latitudes, an exact coincidence in the time of greatest inundation is very improbable. CONCLUDING REMARKS ON DELTAS. Quantity of sediment in river water. Very few satisfactory experiments have as yet been made, to enable us to deter- mine, with any degree of accuracy, the mean quantity of earthy matter discharged annually into the sea by some one of the principal rivers of the earth. Hartsoeker computed the Rhine to contain in suspension, when most flooded, one part in a hundred of mud in volume *. By several observations of Sir George Staunton, it appeared that the water of the Yellow River in China contained earthy matter in the proportion of one part to two hundred, and he calculated that it brought down in a single hour two million cubic feet of earth, or forty- eight million daily ; so that, if the Yellow Sea be taken to be one hundred and twenty feet deep, it would require seventy days for the river to convert an English square mile into firm land, and twenty-four thousand years to turn the whole sea into terra firma, assuming it to be one hundred and twenty-five thousand square miles in area f . Manfredi, the celebrated Italian hydrographer, conceived the average proportion of sedi- ment in all the running water on the globe, which reached the sea, to be -^- 5 , and he imagined that it would require a thou- sand years for the sediment carried down to raise the general level of the sea about one foot. Some writers, on the contrary, as De Maillet, have declared the most turbid waters to contain far less sediment than any of the above estimates would im- * Comment. Bonon., vol. ii. part i. p. 237. t Staunton's Embassy to China, London, 1797, 4to, vol. ii. p. 408. Ch. XIV.] IN RIVER WATER. 283 port ; and there is so much contradiction and inconsistency in the facts and speculations hitherto promulgated on the subject, that we must wait for additional experiments before we can form any opinion on the question. RennelTs estimate of the mud carried down by the Ganges. One of the most extraordinary statements is that of Major Rennell, in his excellent paper, before referred to, on the Delta of the Ganges. ' A glass of water,' he says, ' taken out of this river when at its height, yields about one part in four of mud. No wonder then that the subsiding waters should quickly form a stratum of earth, or that the delta should encroach on the sea * !' The same hydrographer computed with much care the number of cubic feet of water discharged by the Ganges into the sea, and estimated the mean quantity through the v:hole year to be 180,000 cubic feet in a second. When the river is most swollen, and its velocity much accelerated, the quantity is 405,000 cubic feet in a second. Other writers agree that the violence of the tropical rains, and the fineness of the alluvial particles in the plains of Bengal, cause the waters of the Ganges to be charged with foreign matter to an extent wholly unequalled by any large European river during the greatest floods. We have already alluded to the frequent sweeping down of large islands by the Ganges ; and Major R. H. Colebrooke, in his account of the course of the Ganges, relates examples of the rapid filling up of some branches of the river, and the excavation of new channels, where the number of square miles of soil removed in a short time (the column of earth being one hundred and fourteen feet high) was truly astonishing. Forty square miles, or 25,600 acres, are mentioned as having been carried away, in one locality, in the course of a few years f . But, although we can readily believe the proportion of sedi- ment in the waters of the Ganges to exceed that of any river in northern latitudes, we are somewhat staggered by the results to * Phil. Trans., 1781. t Trans, of the Asiatic Society, vol. vii, p. 14. 284 PROPORTION OF SEDIMENT [Ch. XIV. which we must arrive if we compare the proportion of mud, as given by Rennell, with his computation of the quantity of water discharged, which latter is probably very correct. If it were true that the Ganges, in the flood-season, contained one part in four of mud, we should then be obliged to suppose that there passes down, every four days, a quantity of mud equal in volume to the water which is discharged in the course of twenty-four hours. If the mud'be assumed to be equal to one-half the specific gravity of granite (it would, however,, be more), the weight of matter daily carried down in the flood- season would be about equal to seventy-four times the weight of the Great Pyramid of Egypt *. Even if it could be proved that the turbid waters of the Ganges contain one part in a hundred of mud, which is possible, and which is affirmed to be the case in regard to the Rhine, we should be brought to the extraordinary conclusion, that there passes down every day into the Bay of Bengal a mass more than equal in weight and bulk to the Great Pyramid. The most voluminous current of lava which has flowed from Etna within historical times was that of 1669. Ferrara, after correcting Borrelli's estimate, calculated the quantity of cubic yards of lava in this current at one hundred and forty millions. Now, this would not equal in bulk one- fifteenth of the sedi- mentary matter which is carried down in a single year by the Ganges, assuming the average proportion of mud to water to be one part in one hundred, so that, allowing fifteen grand eruptions in a century, it would require an hundred Etnas to transfer a mass of lava from the subterranean regions to the * According to Rennell, the Ganges discharges, in the flood-season, 405,000 cubic feet of water per second, which gives in round numbers 100,000 cubic feet of mud per second, which X 86,400, the number of seconds in twenty-four hours, = 8,640,000,000, the quantity of cubic feet of mud going down the Ganges per diem. Assuming the specific gravity of mud to be half that of granite, the matter would equal 4,320,000,000 feet of granite. Now, about twelve and a half cubic feet of granite weigh one ton ; and it is computed that the Great Pyramid of Egypt, if it were a solid mass of granite, would weigh about 6,000,000 of tons. Ch.XIV.] IN* RIVER WATER. 285 surface equal in volume to the mud carried down in the same time from the Himalaya mountains into the Bay of Bengal *. As considerable labour has been bestowed in computing the volume of lava-streams in Sicily, Campania, and Auvergne, it is somewhat extraordinary that so few observations have been made on the quantity of matter transported by aqueous agents from one part of the earth to another. It would certainly not be difficult to approximate to the amount of sediment carried down annually by some of the largest rivers, such as the Ama- zon, Mississippi, Ganges, and others, because the earthy par- ticles conveyed by them to their deltas are fine, and somewhat uniformly spread throughout the stream, and the principal efflux takes place within a limited period during the season of inundation. Arguments have been expended in vain for half a century in controverting the opinion of those who imagine the agency of running water in the existing state of things, even if continued through an indefinite lapse of ages, to be insignifi- cant, or at least wholly incompetent to produce considerable inequalities on the earth's surface. Some matter-of-fact data should now be accumulated, and we may confidently affirm that, when the aggregate amount of solid matter transported by rivers in a given number of centuries from a large continent shall be reduced to arithmetical computation, the result will appear most astonishing to those who are not in the habit of reflecting how many of the mightiest operations in nature are effected insensibly, without noise or disorder. The volume of matter carried into the sea in a given time being once ascer- tained, every geologist will admit that the whole, with some slight exceptions, is subtracted from valleys, not from the tops of intervening ridges or the summits of hills ; in other words, f According to Ferrara's calculation, about 140,000,000 of cubic yards of lava were poured from the crater of Etna in 1669. This X 27, will give 3.780.000.000 of cubic feet, which would be about one-fifteenth of the amount of mud carried down by the Ganges in a year; for, assuming the average proportion of mud to be one part in a hundred, this would give on an average 1800 cubic feet per second: 1800 X 31,557,600 (the number of seconds in a Julian year), gives 56,803,680,000. 286 GROUPING OF STRATA IN DELTAS. [Ch, XIV. that ancient valleys have been widened and deepened, or new ones formed, to the extent of the space which the new deposits, when consolidated, would occupy. Grouping of Strata in Deltas. The changes which have taken place in deltas, even since the times of history, may sug- gest many important considerations in regard to the manner of distribution of sediment in subaqueous deposits. Notwith- standing frequent exceptions arising from the interference of a variety of causes, there are some general laws of arrangement which must evidently hold good in almost all the lakes and seas now filling up. If a lake, for example, be encircled on two sides by lofty mountains, receiving from them many rivers and torrents of different sizes, and if it be bounded on the other sides, where the surplus waters issue, by a comparatively low country, it is not difficult to define some of the leading geolo- gical features which will characterize the lacustrine formation when this basin shall have been gradually converted into dry land by influx of fluviatile sediment. The strata would be divisible into two principal groups : the older comprising those deposits which originated on the side adjoining the mountains, where numerous deltas first began to form; and the newer group consisting of beds deposited in the more central parts of the basin, and towards the side farthest from the mountains. The following characters would form the principal marks of distinction between the strata in each series. The more ancient system would be composed, for the most part, of coarser ma- terials, containing many beds of pebbles and sand often of great thickness, and sometimes dipping at a considerable angle. These, with associated beds of finer ingredients, would, if traced round the borders of the basin, be seen to vary greatly in colour and mineral composition, and would also be very irregular in thickness. The beds, on the contrary, in the newer group, would consist of finer particles, and would be horizontal, or very slightly inclined. Their colour and mineral composition would be very homogeneous throughout large areas, and would differ from almost all the separate beds in the older series. Ch. XIV.] GROUPING OF STRATA IN DELTAS. 287 The following are the causes of the diversity here alluded to between the two great members of the lacustrine formation. When the rivers and torrents first reach the edge of the lake, the detritus washed down by them from the adjoining heights sinks at once into deep water, all the heavier pebbles and sand subsiding near the shore. The finer mud is carried somewhat farther out, but not to the distance of many miles, for the greater part may be seen, where the Rhone enters the Lake of Geneva, to fall down in clouds to the bottom not far from the river's mouth. Certain alluvial tracts are soon formed at the mouths of every torrent and river, and many of these, in the course of ages, become several miles in length. Pebbles and sand are then transported farther from the mountains, but in their passage they decrease in size by attrition, and are in part converted into mud and sand. At length some of the nume- rous deltas, which are all directed towards a common centre, approach near to each other those of adjoining torrents be- come united, and are merged, in their turn, in the delta of the largest river, which advances most rapidly into the lake, and renders all the minor streams, one after the other, its tribu- taries. The various mineral ingredients of each are thus blended together into one homogeneous mixture, and the sedi- ment is poured out from a common channel into the lake. As the average size of the transported particles decreases continually, so also the force and volume of the current aug- ments, and thus the newer deposits are diffused over a wider area, and are consequently more horizontal than the older. When there were many independent deltas near the borders of the basin, their separate deposits differed entirely from each other. We may suppose that one was charged, like the Arve where it joins the Rhone, with white sand and sediment, chiefly derived from decomposed granite that another was black, like many streams in the Tyrol, flowing from incoherent rocks of dark slate that a third was coloured by ochreous sediment, like the Red River in Louisiana and that a fourth, like the Elsa in Tuscany, held much carbonate of lime in solution. At 288 CONVERGENCE OF DELTAS. [Ch. XIV. first, they would each form distinct deposits of sand, gravel, limestone, marl, or other materials; but after their junction, new chemical combinations and distinct colours would be the result, and the particles, having been conveyed ten, twenty, or a greater number of miles over alluvial plains, would become finer. In deltas where the causes are more complicated, and where tides and currents partially interfere, the above description would only be applicable, with certain modifications ; but if a series of earthquakes accompany the growth of a delta, and change the levels of the land from time to time, as in the region where the Indus now enters the sea, and others hereafter to be mentioned, the phenomena will then depart widely from the ordinary type. Convergence of Deltas. If we possessed an accurate series of maps of the Adriatic for many thousand years, our retro- spect would, without doubt, carry us gradually back to the time when the number of rivers descending from the moun- tains into that gulf by independent deltas, was far greater in number. The deltas of the Po and the Adige, for instance, would separate themselves within the human era, as, in all pro- bability, would those of the Isonzo and the Torre. If, on the other hand, we speculate on future changes, we may anticipate the period when the number of deltas will greatly diminish ; for the Po cannot continue to encroach at the rate of a mile in a century, and other rivers to gain as much in six or seven centuries upon the shallow gulf, without new junctions occur- ring from time to time, so that Eridanus, ' the king of rivers,' will continually boast a greater number of tributaries. The Ganges and Burrampooter have probably become confluent within the historical era; and the date of the junction of the Red River and the Mississippi would, in all likelihood, have been known, if America had not been so recently discovered. The union of the Tigris and the Euphrates must undoubtedly have been one of the modern geographical changes on our earth, and similar remarks might be extended to many other regions. Ch.XIV.] GROUPING OF DEPOSITS IN DELTAS. 289 Formation of Conglomerates. Along the base of the Mari- time Alps, between Toulon and Genoa, the rivers, with few exceptions, are now forming strata of conglomerate and sand. Their channels are often several miles in breadth, some of them being dry, and the rest easily forded for nearly eight months in the year ; whereas during the melting of the snow they are swollen, and a great transportation of mud and pebbles takes place. In order to keep open the main road from France to Italy, now carried along the sea-coast, it is necessary to remove annually great masses of shingle, brought down during the flood-season. A portion of the pebbles are seen in some loca- lities, as near Nice, to form beds of shingle along the shore, but the greater part are swept into a deep sea. The small pro- gress made by the deltas of minor rivers on this coast need not surprise us, when we recollect that there is sometimes a depth of two thousand feet at a few hundred yards from the beach, as near Nice. Similar observations might be made respecting a large proportion of the rivers in Sicily, and, among others, respecting that which, immediately north of the port of Mes- sina, hurries annually vast masses of granitic pebbles into the sea. When the deltas of rivers having many mouths converge, a partial union at first takes place by the confluence of some one or more of their arms ; but it is not until the main trunks are connected above the head of the common delta, that a complete intermixture of their joint waters and sediment takes place. The union, therefore, of the Po and Adige, and of the Ganges and Burrampooter, is still incomplete. If we reflect on the geographical extent of surface drained by rivers such as now enter the bay of Bengal, and then consider how complete the blending together of the greater part of their transported mat- ter has already become, and throughout how vast a delta it is spread by numerous arms, we no longer feel so much surprise at the area occupied by some ancient formations of homogene- ous mineral composition. But our surprise will be still further lessened when we afterwards inquire into the action of tides VOL. I. U 290 STRATIFICATION OF DEPOSITS IN DELTAS. [Ch, XIV. and currents, in disseminating the matter accumulated in va- rious deltas. Stratification of Deposits in Deltas. That the matter car- ried by rivers into seas and lakes is not thrown in confused and promiscuous heaps, but is spread out far and wide along the bottom, is well ascertained ; and that it must for the most part be divided into distinct strata, may in part be inferred where it cannot be proved by observation. The horizontal arrange- ment of the strata, when laid open to the depth of twenty or thirty feet in the delta of the Ganges and in that of the Mis- sissippi, is alluded to by many writers ; and the same disposi- tion is well known to obtain in all modern deposits of lakes and estuaries. Natural divisions are often occasioned by the interval of time which separates annually the deposition of matter during the periodical rains, or melting of the snow upon the mountains. The deposit of each year acquires some degree of consistency before that of the succeeding year is superimposed. A variety of circumstances also give rise annually to slight variations in colour, fineness of the particles, and other characters. Alter- nations of strata distinct in texture, mineral ingredients, or organic contents, are produced by numerous causes. Thus, for example, at one period of the year, drift wood may be carried down, and at another mud, as was before stated to be the case in the delta of the Mississippi ; or at one time when the volume and velocity of the stream are greatest, pebbles and sand may be spread over a certain area, over which, when the waters are low, fine matter or chemical precipitates are formed. During inundations the current of fresh water often repels the sea for many miles ; but when the river is low, salt water again occupies the same space. When two deltas are con- verging, the intermediate space is often, for reasons before explained, alternately the receptacle of different sediments de- rived from the converging streams. The one is, perhaps, charged with calcareous, the other with argillaceous matter ; or one may sweep down sand and pebbles, the other impal- Ch. XIV.] STRATIFICATION OF DEPOSITS IN DELTAS. 291 pable mud. These differences may be repeated, with con- siderable regularity, until a thickness of hundreds of feet of alternating beds is accumulated. An examination of the strata of shell-marl now forming in the Scotch lakes, or of the sediment termed ' warp/ which subsides from the muddy water of the H umber, and other rivers, shows that recent deposits are often composed of a great number of extremely thin layers, either even or slightly undu- lating, and parallel to the planes of stratification. Sometimes, however, the laminae in modern strata are disposed diagonally at a considerable angle, which appears to take place where there are conflicting movements in the waters. In January, 1829, I visited, in company with Professor L. A. Necker, of Geneva, the confluence of the Rhone and Arve, when those rivers were very low, and were cutting channels through the vast heaps of debris thrown down from the waters of the Arve, in the preceding spring. One of the sand-banks which had formed, in the spring of 1828, where the opposing currents of the two rivers neutralized each other, and caused a retardation in the motion, had been undermined ; and the following is an exact representation of the arrangement of laminae exposed in a vertical section. The length of the portion here seen is No. 6. Talus Section on the banks of the Arve at its confluence with the Rhone, showing the stratification of deposits where currents meet. about twelve feet, and the height five. The strata A A consist of irregular alternations of pebbles and sand in undulating U2 292 CONCLUDING REMARKS ON DELTAS. [Ch. XIV. beds : below these are seams of very fine sand, B B, some as thin as paper, others about a quarter of an inch thick. The strata c c are composed of layers of fine greenish-gray sand, as thin as paper. Some of the inclined beds will be seen to be thicker at their upper, others at their lower extremity, the in- clination of some being very considerable. These layers must have accumulated one on the other by lateral apposition, pro- bably when one of the rivers was very gradually increasing or diminishing in velocity, so that the point of greatest retardation caused by their conflicting currents shifted slowly, allowing the sediment to be thrown down in successive layers on a sloping bank. The same phenomenon is exhibited in older strata of all ages ; and when we treat of them, we shall en- deavour more fully to illustrate the origin of such a structure. Constant interchange of Land and Sea. We may now con- clude our remarks on deltas, observing that, imperfect as is our information of the changes which they have undergone within the last three thousand years, they are sufficient to show how constant an interchange of sea and land is taking place on the face of our globe. In the Mediterranean alone, many flourish- ing inland towns, and a still greater number of ports, now stand where the sea rolled its waves since the era when civilized nations first grew up in Europe. If we could compare with equal accuracy the ancient and actual state of all the islands and continents, we should probably discover that millions of our race are now supported by lands situated where deep seas pre- vailed in earlier ages. In many districts not yet occupied by man, land animals and forests now abound where the anchor once sank into the oozy bottom. We shall find, on inquiry, that inroads of the ocean have been no less considerable ; and when to these revolutions produced by aqueous causes, we add analogous changes wrought by igneous agency, we shall, per- haps, acknowledge the justice of the conclusion of a great phi- losopher of antiquity, when he declared that the whole land and sea on our globe periodically changed places *. * See an account of the Aristotelian system, p. 17, ante. CHAPTER XV. Destroying and transporting effects of tides and currents Shifting of their posi- tion Differences in the rise of the tides Velocity of currents Causes of currents Action of the sea on the British coast Shetland Islands Large blocks removed Effects of lightning Breach caused in a mass of porphyry Isles reduced to clusters of rocks Orkney Isles East coast of Scotland Stones thrown up on the Bell Rock East coast of England Waste of the cliffs of Holderness, Norfolk, and Suffolk Silting up of estuaries Origin of submarine forests Yarmouth estuary Submarine forests Suffolk coast Dunwich Essex coast Estuary of the Thames Goodwin sands Coast of Kent Formation of Straits of Dover South coast of England Coast of Sussex Coast of Hants Coast of Dorset Portland Origin of the Chesil Bank Cornwall Lionesse tradition Coast of Brittany. DESTROYING AND TRANSPORTING EFFECTS OF TIDES AND CURRENTS. ALTHOUGH the movements of great bodies of water, termed tides and currents, are in general due to very distinct causes, we cannot consider their effects separately, for they produce, by their joint action, those changes which are subjects of geological inquiry. We may view these forces as we before considered rivers, first as employed in destroying portions of the solid crust of the earth, and removing them to other localities; secondly, as reproductive of new strata. Some of the principal currents which traverse large regions of the globe depend on permanent winds, and these on the rotation of the earth on its axis, and its position in regard to the sun : they are causes, therefore, as constant as the tides themselves, and, like them, depend on no temporary or accidental circumstances, but on the laws which preside over the motions of the heavenly bodies. Currents shift their position. But although the sum of their influence in altering the surface of the earth may be very constant throughout successive epochs, yet the points where these operations are displayed in the fullest energy shift per- petually. The height to which the tides rise, and the violence 294 RISE OF THE TIDES. [Ch. XV. and velocity of currents, depend in a great measure on the actual configuration of the land, the contour of a long line of continental or insular coast, the depth and breadth of channels, the peculiar form of the bottom of seas in a word, on a com- bination of circumstances which are made to vary continually by many igneous and aqueous causes, and among the rest, by tides and currents. Although these agents, therefore, of decay and reproduction, are local in reference to periods of short duration, such as those which history in general embraces, they are nevertheless universal, if we extend our views to a sufficient lapse of ages. Differences in the Rise of the Tides. The tides, as is well known, rise in certain channels, bays, and estuaries, to an ele- vation far above the average height of the same tides in more open parts of the coast, or on islands in the main ocean. In all lakes, and in most inland seas, the tides are not perceptible. In the Mediterranean, even, deep and extensive as is that sea, they are only sensible in certain localities, and they then rarely rise more than six inches above the mean level. In the Straits of Messina, however, there is an ebb and flow every six hours, to the amount of two feet, but this elevation is partly due to the peculiar set of the currents. In islands remote from the shore, the rise of the tides is slight, as at St. Helena, for ex- ample, where it rarely exceeds three feet *. In the estuary of the Severn, the rise at King-Road, near Bristol, is forty-two feet ; and at Chepstow on the Wye, a small river which opens into the same estuary, above fifty feet, and sometimes sixty- nine and even seventy-two feetf . All the intermediate eleva- tions may be found at different places on our coast. Thus, at Milford Haven the rise is thirty-six feet ; at London, and the promontory of Beachy Head, eighteen feet ; at the Needles, in the Isle of Wight, nine feet ;" at Wey mouth, seven ; at Lowe- stoff, about five ; at Great Yarmouth, still less. A current * Romme, Vents et Courans, vol. ii. p. 2. Rev. F, Fallows; Quart, Journ. of Sci., March, 1829. f On the authority of Captain Beaufort, R.N. Ch.XV.] CAUSES OF CURRENTS. 295 which sets in on the French coast, to the west of Cape La Hague, becomes pent up by Guernsey, Jersey, and other islands, till the rise of the tide is from twenty to forty-five feet, which last height is attained at Jersey, and at St. Malo's, a sea-port of Brittany. Velocity of Currents. On our eastern coast the strongest currents seldom exceed four miles and a half an hour. The current which runs through the Race of Alderney, between the island of that name and the main land, has a velocity of above eight English miles an hour. Captain Hewett found that in the Pentland Firth the stream, in ordinary spring tides, runs ten miles and a half an hour, and about thirteen miles during violent storms. The greatest velocity of the current through the shoots,' or new passage, in the Bristol Channel, is four- teen miles an hour, and Captain King observed, in his recent survey of the Straits of Magellan, that the tide ran at the same rate through the f First Narrows.' Causes of Currents. That movements of no inconsiderable magnitude should be impressed on an expansive ocean, by winds blowing for many months in one direction, may easily be conceived, when we observe the effects produced in our own seas by the temporary action of the same cause. It is well known that a strong south-west or north-west wind invariably raises the tides to an unusual height along the east coast of England and in the Channel ; and that a north-west wind of any continuance causes the Baltic to rise two feet and upwards above its ordinary level. Smeaton ascertained by experiment that, in a canal four miles in length, the water was kept up four inches higher at one end than at the other, merely by the action of the wind along the canal ; and Rennell informs us that a large piece of water, ten miles broad, and generally only three feet deep, has, by a strong wind, had its waters driven to one side, and sustained so as to become six feet deep, while the windward side was laid dry *. As water, therefore, he ob- serves, when pent up so that it cannot escape, acquires a higher * Rennell on the Channel-current, 296 GULF STREAM. [Ch. XV. level, so, iii a place where it can escape, the same operation produces a current ; and this current will extend to a greater or less distance,, according to the force by which it is produced. The most extensive and best determined of all currents is the Gulf stream which sets westward in tropical regions ; and, after doubling the Cape of Good Hope, where it runs nearly at the rate of two miles an hour, inclines considerably to the north- ward, along the western coast of Africa, then crosses the At- lantic, and, having accumulated in the Gulf of Mexico, passes out at the Straits of Bahama, with a velocity of four miles an hour, which is not reduced to two miles until the stream has proceeded to the distance of eighteen hundred miles in the direction of Newfoundland : near that island it meets with a current setting southward from Baffin's Bay, on the coast of Greenland, and is thereby deflected towards the east. One branch extends in that direction, while another runs towards the north; so that fruits, plants, and wood, the produce of America and the West Indies, are drifted to the shores of Ire- land, the Hebrides, and even to Spitzbergen. In describing the destroying effects of tides and currents, it will be necessary to enter into some detail, because we have not the advantage here, as in the case of the deltas of many rivers, of viewing the aggregate mass which has resulted from the con- tinual transportation of matter, for many centuries, at certain points. We must infer the great amount of accumulation as a corollary from the proofs adduced of the removing force ; and this it will not be difficult to show is, on the whole, greater than that of running water on the land. Action of the Sea on the British Coasts. If we follow the eastern and southern shores of the British islands, from our Ultima Thule in Shetland to the Land's End in Cornwall, we shall find evidence of a series of changes since the historical era, very illustrative of the kind and degree of force exerted by the agents now under consideration. In this survey we shall have an opportunity of tracing the power of the sea on islands, promontories, bays, and estuaries ; on bold, lofty cliffs, as well Ch. XV.] ROCK-MASSES DRIFTED BY THE SEA. 297 as on low shores ; and on every description of rock and soil, from granite to blown sand. We shall afterwards explain, by reference to other regions, some phenomena of which our own coast furnishes no examples. Shetland Islands. The northernmost group of the British islands, the Shetland, are composed of a great variety of pri- mary and trap rocks, including granite, gneiss, mica- slate, ser- pentine, greenstone, and many others, with some secondary rocks, chiefly sandstone and conglomerate. These isles are exposed continually to the uncontrolled violence of the Atlan- tic, for no land intervenes between their western shores and America. The prevalence, therefore, of strong westerly gales causes the waves to be sometimes driven with irresistible force upon the coast, while there is also a current setting from the north. The spray of the sea aids the decomposition of the rocks; and prepares them to be breached by the mechanical force of the waves. Steep cliffs are hollowed out into deep caves and lofty arches ; and almost every promontory ends in a cluster of rocks, imitating the forms of columns, pinnacles, and obelisks. Drifting of large masses of rock. Modern observations show that the reduction of continuous tracts to such insular masses is a process in which Nature is still actively engaged. The Isle of Stenness,' says Dr. Hibbert, e presents a scene of unequalled desolation. In stormy winters, huge blocks of stones are overturned, or are removed from their native beds, and hurried up a slight acclivity to a distance almost incredible. In the winter of 1802, a tabular-shaped mass, eight feet two inches by seven feet, and five feet one inch thick, was dislodged from its bed, and removed to a distance of from eighty to ninety feet. I measured the recent bed from which a block had been carried away the preceding winter (A.D. 1818), and found it to be seventeen feet and a half by seven feet, and the depth two feet eight inches. The removed mass had been borne to a distance of thirty feet, when it was shivered into thirteen or more lesser fragments, some of which were carried 298 ACTION OF THE SEA ON [Ch. XV. still farther, from thirty to one hundred and twenty feet. A block, nine feet two inches by six feet and a half, and four feet thick, was hurried up the acclivity to a distance of one hundred and fifty feet V At Northmavine, also, angular blocks of stone have been removed in a similar manner to considerable distances by the waves of the sea, some of which are represented in the annexed figure, No. 7f . No. 7. Stony fragments drifted by the sea. Northmavine, Shetland. Effects of Lightning. In addition to numerous examples of masses detached and driven by the tides and currents from their place, some remarkable effects of lightning are recorded in these isles. At Funzie, in Fetlar, about the middle of the last century, a rock of mica-schist, one hundred and five feet long, ten feet broad, and in some places four feet thick, was in an instant torn by a flash of lightning from its bed, and broken into three large, and several lesser fragments. One of these, twenty-six feet long, ten feet broad and four feet thick, was simply turned over. The second, which was twenty-eight feet long, seventeen broad, and five feet in thickness, was hurled across a high point to the distance of fifty yards. Another broken mass, about forty feet long, was thrown still farther, * Dr. Hibbert, Description of the Shetland Islands, p. 527. Edin., 1822. f For this, and the three following representations of rocks in the Shetland Isles, I am indebted to Dr. Hibbert's work before cited, which is rich in antiqua- rian and geological research. Ch. XV.] THE SHETLAND ISLANDS. 299 but in the same direction, quite into the sea. There were also many lesser fragments scattered up and down *. When we thus see electricity co-operating with the violent movements of the ocean in heaping up piles of shattered rocks on dry land, and beneath the waters, we cannot but admit that a region which shall be the theatre, for myriads of ages, of the action of such disturbing causes, will present, at some future period, a scene of havoc and ruin that may compare with any now found by the geologist on the surface of our continents, raised as they all have been in former ages from the bosom of the deep. We have scarcely begun, as yet, to study the effects of a single class of the mighty instruments of change and disorder now operating on our globe ; and yet geologists have presumed to resort to a nascent order of things, or to revolutions in the economy of Nature, to explain every obscure phenomenon ! In some of the Shetland Isles, as on the west of Meikle Roe, dikes, or veins of soft granite, have mouldered away ; while the matrix in which they were inclosed, being of the same sub- stance, but of a firmer texture, has remained unaltered. Thus, long narrow ravines, sometimes twenty feet wide, are laid open, and often give access to the waves. After describing some huge cavernous apertures into which the sea flows for two hun- dred and fifty feet in Roeness, Dr. Hibbert enumerates other ravages of the ocean. ' A mass of rock, the average dimen- sions of which may perhaps be rated at twelve or thirteen feet square, and four and a half or five in thickness, was first moved from its bed, about fifty years ago, to a distance of thirty feet, and has since been twice turned over.' Passage forced by the sea through porphyritic rocks. ' But the most sublime scene is where a mural pile of porphyry, escap- ing the process of disintegration that is devastating the coast, appears to have been left as a sort of rampart against the inroads of the ocean ; the Atlantic, when provoked by wintry gales, batters against it with all the force of real artillery the * Dr. Hibbert, from MSS. of Rev. George Low, of Fetlar. 300 ACTION OF THE SEA ON [Ch. XV. No. 8. Grind of the Navir Passage forced by the sea through rocks of hard porphyry. waves having, in their repeated assaults, forced themselves an entrance. This breach, named the Grind of the Navir (No. 8), is widened every winter by the overwhelming surge that, find- ing a passage through it, separates large stones from its sides, and forces them to a distance of no less than one hundred and eighty feet. In two or three spots, the fragments which have been detached, are brought together in immense heaps, that appear as an accumulation of cubical masses, the product of some quarry *.' It is evident, from this example, that although the greater indestructibility of some rocks may enable them to withstand, for a longer time, the action of the elements, yet they cannot permanently resist. There are localities in Shetland, in which rocks of almost every variety of mineral composition are suf- fering disintegration : thus the sea makes great inroads on the clay slate of Fitfel Head, on the serpentine of the Vord Hill in Fetlar, and on the mica- schist of the Bay of Triesta, on the east coast of the same isle, which decomposes into angular blocks. The quartz rock on the east of Walls, and the gneiss and mica-schist of Garthness, suffer the same fate. Destruction of islands. Such devastation cannot be inces * Hibbert, p. 528, Ch. XV.] THE SHETLAND ISLANDS. 301 santly committed for thousands of years without dividing islands, until they become at last mere clusters of rocks, the last shreds of masses once continuous. To this state many appeal- to have been reduced, and innumerable fantastic forms are assumed by rocks adjoining these isles, to which the name of Drongs is applied, as it is to those of similar shape in Feroe. No. 9. Granitic rocks named the Drongs, letween Papa Stour and Hillsicick Xess. The granitic rocks (No. 9), between Papa Stour and Hills wick Ness afford an example. A still more singular cluster of rocks is seen to the south of Hillswick Ness (No. 10), which pre- sents a variety of forms as viewed from different points, and has often been likened to a small fleet of vessels with spread sails *. No. 10. Granitic rocks to the south ofHillsivick Xess, Shetland. * Hibbert, p. 519. 302 ENCROACHMENTS OF THE SEA ON [Ch. XV. We may imagine that in the course of time Hillswick Ness itself may present a similar wreck, from the unequal decompo- sition of the rocks whereof it is composed, consisting of gneiss and mica-schist, traversed in all directions by veins of felspar porphyry. Midway between the groups of Shetland and Orkney is Fair Island, said to be composed of sandstone with high perpendicu- lar cliffs. The current runs with such velocity, that during a calm, and when there is no swell, the rocks on its shores are white with the foam of the sea driven against them. The Orkneys, if carefully examined, would probably afford as much illustration of our present topic as the Shetland Islands. The north-east promontory of Sanda, one of these isles, has been cut off in modern times by the sea, so that it became what is now called Start Island, where a lighthouse was erected in 1807, since which time the new strait has grown broader. East coast of Scotland. To pass over to the main land of Scotland, we find that, in Inverness- shire, there have been in- roads of the sea at Fort George, and others in Murrayshire, which have swept away the old town of Findhorn. On the coast of Kincardineshire, an illustration was afforded, at the close of the last century, of the effect of promontories in pro- tecting a line of low shore. The village of Mathers, two miles south of Johnshaven, was built on an ancient shingle beach, protected by a projecting ledge of limestone rock. This was quarried for lime to such an extent, that the sea broke through, and in 1795 carried away the whole village in one night, and penetrated one hundred and fifty yards inland, where it has maintained its ground ever since, the new village having been built farther inland on the new shore. In the Bay of Montrose, we find the North Esk and the South Esk rivers pouring annually into the sea large quantities of sand and pebbles, yet they have formed no deltas ; for the tides scour out the channels, and the current, setting across their mouths, sweeps away all the materials. Considerable beds of shingle, brought down by the North Esk, are seen along the beach. Ch, XV.] THE EAST COAST OF SCOTLAND. 303 Proceeding southwards, we find that at Arbroath, in Forfar- shire, which stands on a rock of red sandstone, gardens and houses have been carried away within the last thirty years by encroachments of the sea. It has become necessary to remove the lighthouses at the mouth of the estuary of the Tay, in the same county, at Button Ness, which were built on a tract of blown sand, the sea having encroached for three-quarters of a mile. Force of Currents in Estuaries. A good illustration was afforded, during the building of the Bell Rock Lighthouse, at the mouth of the Tay, of the power which currents in estuaries can exert at considerable depths, in scouring out the channel. The Bell Rock is a sunken reef, consisting of red sandstone, being from twelve to sixteen feet under the surface at high water, and about twelve miles from the main land. At the dis- tance of one hundred yards, there is a depth, in all directions, of two or three fathoms at low water. The perpendicular rise and fall of the spring tides is fifteen feet, and at neap tides eight feet ; their velocity varying from one to three miles per hour. In 1807, during the erection of the lighthouse, six large blocks of granite, which had been landed on the reef, were removed by the force of the sea, and thrown over a rising ledge to the dis- tance of twelve or fifteen paces ; and an anchor, weighing about 22 cwt., was thrown up upon the rock *. Mr. Stevenson informs us, moreover, that drift stones, measuring upwards of thirty cubic feet, or more than two tons weight, have, during storms, been often thrown upon the rock from the deep water f. Submarine forests. Among the proofs that the sea has en- croached both on the estuaries of the Tay and Forth, may be mentioned the submarine forests which have been traced for several miles by Dr. Fleming, along the margins of those estua- ries on the north and south shores of the county of Fife J. * Account of the Erection of the Bell Rock Lighthouse, p. 163. f Ed. Phil. Journ., vol. iii. p. 54, 1820. $ Quarterly Journal of Science, &c., No, XIII. new series, March, 1830. 304 ENCROACHMENTS OF THE SEA ON [Ch. XV. The alluvial tracts, however, on which such forests grow, gene- rally occupy spaces which may be said to be in dispute between the river and the sea, and to be alternately lost and won. Estuaries (a term which we confine to inlets entered both by rivers and tides of the sea) have a tendency to become silted up in parts; but the same tracts, after remaining dry, perhaps, for thousands of years, are again liable to be overflowed, for they are always low, and, if inhabited, must generally be secured by artificial embankments. Meanwhile the sea devours, as it ad- vances, the high as well as the low parts of the coast, breaking down, one after another, the rocky bulwarks which protect the mouths of estuaries. The changes of territory, therefore, within the general line of coast are all of a subordinate nature, in no way tending to arrest the march of the great ocean, nor to avert the destiny eventually awaiting the whole region ; they are like the petty wars and conquests of the independent states and republics of Greece, while the power of Macedon was stea- dily pressing on, and preparing to swallow up the whole. On the coast of Fife, at St. Andrew's, a tract of land which intervened between the castle of Cardinal Beaton and the sea has been entirely swept away, as were the last remains of the Priory of Crail, in the same county, in 1803. On both sides of the Frith of Forth, land has been consumed ; at North Berwick in particular, and at Newhaven, where an arsenal and dock, built in the reign of James IV., in the fifteenth century, has been overflowed. East coast of England. -If we now proceed to the English coast, we find records of numerous lands having been de- stroyed in Northumberland, as those near Bamborough and Holy Island, and at Tynemouth castle, which now overhangs the sea, although formerly separated from it by a strip of land. At Hartlepool, and several other parts of the coast of Durham composed of magnesian limestone, the sea has made considerable inroads. Almost the whole coast of Yorkshire, from the mouth of the Tees to that of the Humber, is in a state of gradual dila- pidation. That part of the cliffs which consists of lias, the oolite Ch. XV.] THE EAST COAST OF ENGLAND. 305 series, and chalk, decays slowly. They present abrupt and naked precipices, often three hundred feet in height ; and it is only at a few points that the grassy covering of the sloping talus marks a temporary relaxation of the erosive action of the sea. The chalk cliffs are washed into caves in the project- ing headland of Flamborough, where they are decomposed by the salt vapours, and slowly crumble away. But the waste is most rapid between that promontory and Spurn Point, or the coast of Holderness, as it is called. This tract consists chiefly of beds of clay, gravel, sand, and chalk rubble. The irregu- lar intermixture of the argillaceous beds causes many springs to be thrown out, and this facilitates the undermining process, the waves beating against them, and a strong current setting chiefly from the north. The wasteful action is very conspi- cuous at Dimlington Height, the loftiest point in Holderness, where the beacon stands on a cliff one hundred and forty-six feet above high water, the whole being composed of clay, with pebbles scattered through it *. Coast of Yorkshire. In the old maps of Yorkshire, we find spots, now sand-banks in the sea, marked as the ancient sites of the towns and villages of Auburn, Hartburn, and Hyde. 1 Of Hyde, 1 says Pennant, ' only the tradition is left ; and near the village of Hornsea, a street called Hornsea Beck has long since been swallowed f.' Owthorne and its church have also been in great part destroyed, and the village of Kilnsea ; but these places are now removed farther inland. The rate of en- croachment at Owthorne, at present, is about four yards a year\. Not unreasonable fears are entertained that at some future time the Spurn Point will become an island, and that the ocean, entering into the estuary of the Humber, will cause great devastation . Pennant, after speaking of the silting up of some ancient ports in that estuary, observes, ' But, in return, * Phillips's Geology of Yorkshire, p. 61. f Arctic Zoology, vol. i. p. 10, Introduction. J For this information I am indebted to Mr. Phillips, of York. Phillips's Geology of Yorkshire, p. 60. VOL. I. X 306 ENCROACHMENTS OF THE SEA ON [Ch.XV. the sea has made most ample reprisals ; the site, and even the very names of several places, once towns of note upon the Humber, are now only recorded in history ; and Ravensper was at one time a rival to Hull (Madox, Ant. Exch. i., 422), and a port so very considerable in 1332, that Edward Balliol and the confederated English Barons sailed from hence to invade Scotland; and Henry IV., in 1399, made choice of this port to land at, to effect the deposal of Richard II., yet the whole of it has long since been devoured by the merciless ocean : extensive sands, dry at low water, are to be seen in their stead*.' Pennant describes Spurn Head as a promontory in the form of a sickle, and says the land, for some miles to the north, was s perpetually preyed on by the fury of the German Sea, which devours whole acres at a time, and exposes on the shores con- siderable quantities of beautiful amber f .' According to Bergmann, a strip of land, with several vil- lages, was carried away near the mouth of the H umber in 1475. Lincolnshire. The maritime district of Lincolnshire consists chiefly of lands which lie below the level of the sea, being protected by embankments. Great parts of this fenny tract were, at some unknown period, a woody country, but were afterwards inundated, and are now again recovered from the sea. Some of the fens were embanked and drained by the Romans ; but after their departure the sea returned, and large tracts were covered with beds of silt containing marine shells, now again converted into productive lands. Many dreadful catastrophes are recorded by incursions of the sea, whereby several parishes have been at different times overwhelmed. Norfolk. We come next to the cliffs of Norfolk and Suffolk, where the decay is in general incessant and rapid. At Hun- stanton, on the north, the undermining of the lower arenaceous beds at the foot of the cliff causes masses of red and white chalk to be precipitated from above. Between Hunstanton * Arct, Zool v vol, i, p, 10, Introduction. t Ibid, Ch. XV.] THE EAST COAST OF ENGLAND. 307 and Weybourne, low hills, or dunes, of blown sand, are formed along the shore, from fifty to sixty feet high. They are composed of dry sand, bound in a compact mass by the long creeping roots of the plant called Marram (Arundo arenaria). Such is the present set of the tides, that the harbours of Clay, Wells, and other places, are securely defended by these bar- riers ; affording a clear proof that it is not the strength of the material at particular points that determines whether the sea shall be progressive or stationary, but the general contour of the coast. The waves constantly undermine the low chalk cliffs, covered with sand and clay, between Weybourne and Sherringham, a certain portion of them being annually removed. At the latter town I ascertained, in 1829, some facts which throw light on the rate at which the sea gains upon the land. It was com- puted, when the present inn was built, in 1805, that it would require seventy years for the sea to reach the spot ; the mean loss of land being calculated, from previous observations, to be somewhat less than one yard annually. The distance between the house and the sea was fifty yards ; but no allowance was made for the slope of the ground being from the sea, in conse- quence of which, the waste was naturally accelerated every year, as the cliff grew lower, there being at each succeeding period less matter to remove when portions of equal area fell down. Between the years 1824 and 1829, no less than seven- teen yards were swept away, and only a small garden was then left between the building and the sea. There is now a depth of twenty feet (sufficient to float a frigate) at one point in the harbour of that port, where, only forty-eight years ago, there stood a cliff fifty feet high, with houses upon it ! If once in half a century an equal amount of change were produced at once by the momentary shock of an earthquake, history would be filled with records of such wonderful revolutions of the earth's surface, but, if the conversion of high land into deep sea be gradual, it excites only local attention. The flag-staff of the Preventive Service station, on the south side of this X 2 308 ENCROACHMENTS OF THE SEA. [Ch. XV. harbour, has, within the Jast fifteen years, been thrice removed inland, in consequence of the advance of the sea. Farther to the south we find cliffs, composed, like those of Holderness before mentioned, of alternating strata of blue clay, gravel, loam, and fine sand. Although they sometimes exceed two hundred feet in height, the havoc made on the coast is most formidable. The whole site of ancient Cromer now forms part of the German Ocean, the inhabitants having gradually retreated inland to their present situation, from whence the sea still threatens to dislodge them. In the winter of 1825, a fallen mass was precipitated from near the lighthouse, which covered twelve acres, extending far into the sea, the cliffs being two hundred and fifty feet in height *. The undermining by springs has sometimes caused large portions of the upper part of the cliffs, with houses still standing upon them, to give way, so that it is impossible, by erecting breakwaters at the base of the cliffs, permanently to ward off the danger. On the same coast, the ancient villages of Shipden, Wimp- well, and Eccles, have disappeared ; several manors and large portions of neighbouring parishes having, piece after piece, been swallowed up ; nor has there been any intermission, from time immemorial, in the ravages of the sea along a line of coast twenty miles in length, in which these places stood -\. Hills of blown sand, between Eccles and Winterton, have barred up and excluded the tide for many hundred years from the mouths of several small estuaries; but there are records of nine breaches from twenty to one hundred and twenty yards wide, having been made through these, whereby immense damage was done to the low grounds in the interior. A few miles south of Happisburgh, also, are hills of blown sand, which extend to Yarmouth ; and these are supposed to protect the coast, but in fact their formation proves that a temporary respite of the in- cursions of the sea on this part is permitted by the present set of the tides and currents. Were it otherwise, the land, as we have seen, would give way, though made of solid rock. * Taylor's Geology of East Norfolk, p. 32. f Ibid, Ch. XV.] SILTING UP OF ESTUARIES. 309 Silting up of Estuaries. At Yarmouth, the sea has not ad- vanced upon the sands in the slightest degree since the reign of Elizabeth. In the time of the Saxons, a great estuary ex- tended as far as Norwich, which city is represented, even in the thirteenth and fourteenth centuries, as ' situated on the banks of an arm of the sea.' The sands whereon Yarmouth is built first became firm and habitable ground about the year 1008, from which time a line of dunes has gradually increased in height and breadth, stretching across the whole entrance of the ancient estuary, and obstructing the ingress of the tides so completely, that they are only admitted by the narrow passage which the river keeps open, and which has gradually shifted several miles to the south. The tides at the river's mouth only rise, at present, to the height of three or four feet. By the exclusion of the sea, thousands of acres in the interior have become cultivated lands ; and, exclusive of smaller pools, upwards of sixty fresh-water lakes have been formed, varying in depth from fifteen to thirty feet, and in extent from one acre to twelve hundred *. The Yare, and other rivers, frequently communicate with these sheets of water ; and thus they are liable to be filled up gradually with lacustrine and fluviatile deposits, and to be converted into land covered with forests. When the sea at length returns (for as the whole coast gives way, this must inevitably happen sooner or later), these tracts will be again submerged, and submarine forests may then be found, as along the margins of many estuaries. We may easily conceive that such natural embankments as those thrown by the waves, and subsequently raised by winds, across the entrance of this river, may so shut out the tide, that inland places may become dry which, on the breaching of the barrier, might again be permanently overflowed even at low water ; for the tides are now so depressed, even outside the barrier, that the river is almost in the condition of one which enters an inland sea. Were high tides to recur, the fresh water would * Taylor's Geology of East Norfolk, p. 10. 310 SUBMARINE FORESTS. [Ch. XV. be ponded back during the flow, and would perhaps not entirely escape during the ebb. Submarine forests.- It has been observed, by Dr. Fleming, that the roots of the trees in several submarine forests in Scot- land are in lacustrine silt. The stumps of the trees evidently occupy the position in which they formerly grew 5 and are sometimes from eight to ten feet below high-water mark. The horizontality of the strata, and other circumstances, preclude the supposition of a slide, and the countries in question have been from time immemorial free from violent earthquakes, which might have produced subsidences. He has, therefore, attributed the depression, with much probability, to the drainage of peaty soil on the removal of a seaward barrier. Suppose a lake (like one of those in the valley of the Yare) to become a marsh, and a stratum of vegetable matter to be formed on the surface, of sufficient density to support trees. Let the outlet of the marsh be elevated a few feet only above the rise of the tide. All the strata below the level of the outlet would be kept constantly wet or in a semifluid state, but if the tides rise in the estuary, and the sea encroaches, portions of the gained lands are swept away, and the extremities of the alluvial and peaty strata, whereon the forest grew, are exposed to the sea, and at every ebb tide left dry to a depth equal to the increased fall of the tide. Much water, formerly prevented from es c api by the altitude of the outlet, now oozes out from the moist beds, the strata collapse and the surface of the morass, instead of remaining at its original height, sinks below the level of the sea*. Yarmouth does not project beyond the general line of coast which has been rounded off by the predominating current from the north-west. It must not be imagined, therefore, that the acquisition of new land fit for cultivation in Norfolk and Suf- folk indicates any permanent growth of the eastern limits of * See two papers by the Rev. Dr. Fleming, in the Trans. Roy. Soc. Edin., vol. ix. p. 419, and Quarterly Journ. of Sci., No. 13, new series, March, 1830. For further remarks on Submarine forests, see vol. ii,, chap. 16, Ch. XV.] LOSS OF LAND ON THE SUFFOLK COAST. 311 our island, to compensate its reiterated losses. No delta can form on such a shore. Coast of Suffolk. The cliffs of Suffolk, to which we next proceed, are somewhat less elevated than those of Norfolk, but composed of similar accumulations of alternating clay, sand, and gravel. From Gorleston in Suffolk, to within a few miles north of Lowestoff, the cliffs are slowly undermined. Near the last-mentioned town, there is an inland cliff about sixty feet high, the talus being covered with turf and heath, between which and the sea is a low, flat tract of sand, called the Ness, which gains slowly on the sea. It does not seem difficult to account for the retreat of the sea at this point from its ancient limits, the base of the inland cliff. About a mile off Lowestoff lies the Holm Sand, the highest part of which is dry at low water. The current in the intervening passage, called Lowe- stoff Roads, is a back-water, wherein the tide, instead of obey- ing the general rule along this coast, runs nine hours towards the north, and only three towards the south. Here, therefore, we have an eddy, and the Holm Sand is a bank caused by the meeting of currents, where, as usual, sediment subsides. The channel called Lowestoff Roads is about a mile broad, and the depth varies from twenty to fifty-nine feet at low water. On one side, the current has hollowed out of the Holm Sand a deep curve, called the Hook, and on the other side, precisely opposite, is the projecting point of the Ness *. As the points and bends of a river correspond to each other, sand-bars being thrown up at each point, and the greatest depth being where the river is wearing into the bend, so we find here a shoal in- creasing at the Ness, and deep water preserved in the Hook. We cannot doubt that, at a modern period in the history of this coast, the high cliffs on which Lowestoff stands, were once continuous across the space where the roadstead now is, and where we have stated the present depth to be fifty-nine feet at low water. By the mean of thirty-eight observations, it has been found * See Plan of proposed Canal at Lowestoff, by Cubitt and Taylor, 1826, 312 DESTRUCTION OF DUNWICH BY THE SEA. [Ch. XV. that the difference of high and low tide at Lowestoff is only five feet eight inches* a remarkably slight oscillation for our eastern coast, and which naturally suggests the inquiry whether, at other points where there are inland cliffs, the rise of the tides is below their average level. Destruction of Dunwich by the Sea. The sea undermines the high cliffs a few miles north of Lowestoff,, near Gorton ; as also two miles south of the same town, at Pakefield, a village which has been in part swept away during the present century. From thence to Dunwich the destruction is constant. At the distance of two hundred and fifty yards from the wasting cliff at Pakefield, the sea is sixteen feet deep at low water, and in the roadstead beyond, twenty-four feet. Of the gradual de- struction of Dunwich, once the most considerable sea-port on this coast, we have many authentic records. Gardner, in his history of that borough, published in 1754, shows, by reference to documents beginning with Doomsday Book, that the cliffs at Dunwich, Southwold, Eastern, and Pakefield, have been always subject to wear away. At Dunwich, in particular, two tracts of land which had been taxed in the eleventh century, in the time of King Edward the Confessor, are mentioned, in the Conqueror's survey, made but a few years afterwards, as hav- ing been devoured by the sea. The losses, at a subsequent period, of a monastery at another of several churches after- wards of the old port then of four hundred houses at once of the church of St. Leonard, the high road, town-hall, gaol, and many other buildings, are mentioned, with the dates when they perished. It is stated that, in the sixteenth century, not one quarter of the town was left standing ; yet the inhabitants retreating inland, the name was preserved, as has been the case with many other ports when their ancient site has been blotted out. There is, however, a church, of considerable antiquity, still standing, the last of twelve mentioned in some records. In 1740, the laying open of the churchyard of St. Nicholas and St. Francis, in the sea-cliffs, is well described by Gardner, with * These observations were made by Mr, R. C. Taylor. Ch. XV.] DESTRUCTION OF DUNWICH BY THE SEA. 313 the coffins and skeletons exposed to view, some lying on the beach, and rocked In cradle of the rude imperious surge. Of these cemeteries no remains can now be seen. Ray also says, ( that ancient writings make mention of a wood a mile and a half to the east of Dunwich, the site of which must at pre- sent be so far within the sea *.' This city, once so flourishing and populous, is now a small village, with about twenty houses and one hundred inhabitants. There is an old tradition, ' that the tailors sat in their shops at Dunwich, and saw the ships in Yarmouth Bay; ' but when we consider how far the coast at Lowestoff Ness projects be- tween these places, we cannot give credit to the tale, which, nevertheless, proves how much the inroads of the sea in times of old prompted men of lively imagination to indulge a taste for the marvellous. Gardner's description of the cemeteries laid open by the waves reminds us of the scene which has been so well depicted by Bewick f, and of which numerous points on our coast might have suggested the idea. On the verge of a cliff, which the sea has undermined, are represented the unshaken tower and western end of an abbey. The eastern aisle is gone, and the pillars of the cloister are soon to follow. The waves have almost isolated the promontory, and invaded the cemetery, where they have made sport with the mortal relics, and thrown up a skull upon the beach. In the foreground is seen a broken tombstone, erected, as its legend tells, ( to perpetuate the me- mory ' of one whose name is obliterated, as is that of the county for which he was ' Gustos Rotulorum.' A cormorant is perched on the monument, defiling it, as if to remind some moralizer, like Hamlet, of ' the base uses ' to which things sacred may be turned. Had this excellent artist desired to satirize certain popular theories of geology, he might have inscribed the stone to the memory of some philosopher who taught ' the perma- * Consequences of the Deluge, Phys. Theol. Discourses, f History of British Birds, vol. ii. p. 220, Ed. 1821. 314 ENCROACHMENTS OF THE SEA ON [Ch. XV. nency of existing continents ' * the era of repose ' ' the im- potence of modern causes.' South of Dunwich are two cliffs, called Great and Little Cat Cliff. That which bears the name of Great has become the smallest of the two, and is only fifteen feet high, the more elevated portion of the hill having been carried away ; on the other hand, the Lesser Cat Cliff has gained in importance, for the sea has here been cutting deeper into a hill which slopes towards it. But at no distant period, the ancient names will again become appropriate, for at Great Cat Cliff the base of another hill will soon be reached, and at Little Cat Cliff the sea will, at about the same time, arrive at a valley. The incursions of the sea at Aldborough were formerly very destructive, and this borough is known to have been once situated a quarter of a mile east of the present shore. The inhabitants continued to build farther inland, till they arrived at the extremity of their property, and then the town decayed greatly, but two sand-banks, thrown up at a short distance, now afford a temporary safeguard to the coast. Between these banks and the present shore, where the current now flows, the sea is twenty-four feet deep on the spot where the town for- merly stood. Continuing our survey of the Suffolk coast to the southward, we find that the cliffs of Bawdsey and Felixtow are foundering slowly, and that the point on which Landguard Fort is built suffers gradual decay. It appears that, within the memory of persons now living, the Orwell river continued its course in a more direct line to the sea, and entered to the north instead of the south of the low bank on which the fort last mentioned is built. Essex. Harwich, in Essex, stands on an isthmus, which will probably become an island in little more than half a cen- tury ; for the sea will then have made a breach near Lower Dover Court, should it continue to advance as rapidly as it has done during the last fifty years. Within ten years, there was a considerable space between the battery at Harwich, Ch. XV.] THE EAST COAST OF ENGLAND. 315 built twenty- three years ago, and the sea; part of the for- tification has already been swept away, and the rest overhangs the water. At Walton Naze, in the same county, the cliffs, composed of London clay, capped by the shelly sands of the crag, reach the height of about one hundred feet, and are annually under- mined by the waves. The old churchyard of Walton has been washed away, and the cliffs to the south are continually dis- appearing. Me of Sheppey. On the coast bounding the estuary of the Thames, there are numerous examples both of the gain and loss of land. The Isle of Sheppey, which is now about six miles long by four in breadth, is composed of London clay. The cliffs on the north, which are from sixty to eighty feet high, decay rapidly, fifty acres having been lost within the last twenty years. The church at Minster, now near the coast, is said to have been in the middle of the island fifty years ago ; and it is computed that, at the present rate of destruction, the whole isle will be annihilated in about another half century *. On the coast to the east of Sheppey stands the church of Re- culver, upon a sandy cliff about twenty feet high. In the reign of Henry VIII. it is said to have been nearly a mile dis- tant from the sea. In the < Gentleman's Magazine/ there is a view of it about the middle of the last century, which still re- presents a considerable space as intervening between the north wall of the churchyard and the cliff -f-. About twenty years ago, the waves came within one hundred and fifty feet of the boundary of the churchyard, half of which has since been washed away. The church is now dismantled (1829), and is in great danger ; several houses in a field immediately adjoin- ing having been washed away. Isle of Thanet. In the Isle of Thanet, Bedlam Farm, be- longing to the hospital of that name, has lost eight acres in the * For this information I am indebted to W. Guunell, Esq. f Rev. W. Conybeare's Outlines of Geology, &c. p. 32. 316 GOODWIN SANDS. COAST OF KENT. [Ch. XV. last twenty years, the land being chalk from forty to fifty feet above the level of the sea. It has been computed, that the average waste of the cliff between the North Foreland and the Reculvers, a distance of about eleven miles, is not less than two feet per annum. The chalk cliffs on the south of Thanet, be- tween Ramsgate and Pegwell Bay, have, on an average, lost three feet per annum for the ten last years. Goodwin Sands. The Goodwin Sands lie opposite this part of the Kentish coast. They are about ten miles in length, and are in some parts three, and in others seven miles distant from the shore, and, for a certain space, are laid bare at low water. When the erection of a lighthouse on these sands was in con- templation by the Trinity Board, twelve years since, it was found, by borings, that the bank consisted of fifteen feet of sand, resting on blue clay. An obscure tradition has come down to us, that the estates of Earl Goodwin were situated here, and some have conjectured that they were overwhelmed by the flood mentioned in the Saxon Chronicle, sub anno 1099. The last remains of an island, consisting, like Sheppey, of clay, may, perhaps, have been carried away about that time. Coast of Kent. In the county of Kent, there are other records of waste, at Deal ; and at Dover, Shakspeare's Cliff, composed entirely of chalk, has suffered greatly, and continually diminishes in height, the slope of the hill being towards the land. About twenty years ago, there was an immense land- slip from this cliff, by which Dover was shaken as if by an earthquake. In proceeding from the northern parts of the German Ocean towards the Straits of Dover, the water becomes gradually more shallow, so that in the distance of about two hundred leagues, we pass from a depth of one hundred and twenty, to that of fifty-eight, thirty-eight, twenty-four, and eighteen fathoms. In the same manner, the English channel deepens progressively from Dover to its entrance, formed by the Land's End of England, and the Isle of Ushant on the coast of France ; so that the strait between Dover and Calais Ch. XV.] FORMATION OF THE STRAITS OF DOVER. 317 may be said to form a point of partition between two great in- clined planes, forming the bottom of these seas *. Straits of Dover. Whether England was formerly united with France has often been a favourite subject of speculation ; and in 1753 a society at Amiens proposed this as the subject of a prize essay, which was gained by the celebrated Desma- rest, then a young man. He founded his principal arguments on the identity of composition of the cliffs on the opposite sides of the Channel, on a submarine chain extending from Boulogne to Folkestone, only fourteen feet under low water, and on the identity of the noxious animals in England and France, which could not have swum across the straits, and would never have been introduced by man. He also attributed the rupture of the isthmus to the preponderating violence of the current from the north f . It will hardly be disputed that the ocean might have effected a breach through the land which, in all probabi- lity once united our country to the continent, in the same man- ner as it now gradually forces a passage through rocks of the same mineral composition, and often many hundred feet high, upon our coast. Although the time required for such an operation was pro- bably very great, yet we cannot estimate it by reference to the present rate of waste on both sides of the Channel. For when, in the thirteenth century, the sea burst through the isthmus of Staveren, which formerly united Friesland with North Hol- land, it opened, in about one hundred years, a strait more than half as wide as that which divides England from France, after which the dimensions of the new channel remained almost stationary. The greatest depth of the straits between Dover and Calais is twenty-nine fathoms, which only exceeds by one fathom the greatest depth of the Mississippi at New Orleans. If the moving column of water in the great American river, which, as we before stated, does not flow rapidly, can maintain an open passage to that depth in its alluvial accumulations, * Stevenson on the Bed of the German Ocean. Ed. Phil, Journ., No. V. p. 43, * Cimer, Eloge de Desmarest. 318 ENCROACHMENTS OF THE SEA ON [Cli. XV. still more might a channel of the same magnitude be excavated by the resistless force of the tides and currents of ( the ocean stream,' Trorafjioio /xeya uQevos" and, be- coming charged with impalpable volcanic dust, roll along loose ashes, acquiring such consistency as to deserve their ordinary appellation of ' aqueous lavas.' A brief period of repose ensued, which lasted only until the year 1666, from which time to the present there has been a constant series of eruptions^ with rarely an interval of rest exceeding ten years. During these three centuries no irre- gular volcanic agency has convulsed other points in this district. Brieslak remarked that such irregular convulsions had occurred in the Bay of Naples, in every second century, as, for example, the eruption of the Solfatara in the twelfth, of the lava of Arso, in Ischia, in the fourteenth, and of Monte Nuovo in the six- teenth ; but the eighteenth has formed an exception to this rule, and this seems accounted for by the unprecedented num- ber of eruptions of Vesuvius during that period ; whereas, when the new vents opened, there had always been, as we have seen, a long intermittance of activity in the principal volcano. * Hamilton's Campi Phlegraei, folio, vol. i. p. 62 j and Brieslak, Campanie, tome i. p. 186. CHAPTER XX. Volcanic District of Naples, continued Dimensions and structure of the cone of Vesuvius Dikes in the recent cone, how formed Section though Vesuvius and Somma Vesuvian lavas and minerals Effects of decomposition on lavas Alluvions called ' aqueous lavas' Origin and composition of the matter enveloping Herculaneum and Pompeii Controversies on the subject Condition and contents of the buried cities Proofs of their having suffered by an earthquake Small number of skeletons State of preservation of ani- mal and vegetable substances Rolls of Papyrus Probability of future dis- coveries of MSS. Stabiae Torre del Greco Concluding remarks on the destroying and renovating agency of the Campanian volcanos. VOLCANIC DISTRICT OF NAPLES, continued. Structure of the cone of Fesuvius. BETWEEN the end of the eighteenth century and the year 1822, the great crater of Vesu- vius had been gradually filled by lava boiling up from below, and by scoriae falling from the explosions of minor mouths which were formed at intervals on its bottom and sides. In place of a regular cavity, therefore, there was a rough and rocky plain, covered with blocks of lava and scoriae, and cut by numerous fissures, from which clouds of vapour were evolved. But this state of things was totally changed by the eruption of October, 1822, when violent explosions, during the space of more than twenty days, broke up and threw out all this accumulated mass, so as to leave an immense gulph or chasm, of an irregular, but somewhat elliptical shape, about three miles in circumference when measured along the very sinuous and irregular line of its extreme margin, but somewhat less than three-quarters of a mile in its longest diameter, which was directed from N.E. to S.W.* The depth of this tre- mendous abyss has been variously estimated, for from the hour of its formation it decreased daily, by the dilapidation of its * Account of the Eruption of Vesuvius in October, 1822, by G. P. Scrope, Esq., Journ. of Sci., &c., vol. xv. p. 175. Ch. XX.] STRUCTURE OF THE CONE OF VESUVIUS. 391 sides. It measured, at first, according to the account of some authors, two thousand feet in depth from the extreme part of the existing summit * ; but Mr. Scrope, when he saw it, soon after the eruption, estimated its depth at less than half that quantity. More than eight hundred feet of the cone was car- ried away by the explosions, so that the mountain was reduced in height from about four thousand two hundred to three thousand four hundred feetf. As we ascend the sloping sides, the volcano appears a mass of loose materials a mere heap of rubbish, thrown together without the slightest order ; but on arriving at the brim of the crater, and obtaining a view of the interior, we are agreeably surprised to discover that the conformation of the whole displays in every part the most perfect symmetry and arrangement. The materials are disposed in regular strata slightly undulating, appearing, when viewed in front, to be disposed in horizontal planes. But as we make the circuit of the edge of the crater, and observe the cliffs by which it is encircled projecting or receding in salient or retiring angles, we behold transverse sec- tions of the currents of lava and beds of sand and scoriae, and recognise their true dip. We then discover that they incline outwards from the axis of the cone, at angles varying from 30 to 45. The whole cone, in fact, is composed of a number of concentric coatings of alternating lavas, sand, and scoriae. Every shower of ashes which has fallen from above, and every stream of lava descending from the lips of the crater, have con- formed to the outward surface of the hill, so that one conical envelope may be said to have been successively folded round another, until the aggregation of the whole mountain was com- pleted. The marked separation into distinct beds results from the different colours and degrees of coarseness in the sands, scoriae, and lava, and the alternation of these with each other. The greatest difficulty, on the first view, is to conceive how so much regularity can be produced, notwithstanding the unequal * Mr. Forbes, Account of Mount Vesuvius, Edin. Journ. of Sci., No. xviii.', p. 195, Oct., 1828. f Ibid., p. 194, 392 STRUCTURE OF THE CONE OF VESUVIUS. [Ch. XX. distribution of sand and scoriae, driven by prevailing winds in particular eruptions, and the small breadth of each sheet of lava as it first flows out from the crater. But on a closer examination we find that the appearance of extreme uniformity is delusive, for when a number of beds thin out gradually, and at different points, the eye does not without difficulty recognise the termination of any one stratum, but usually supposes it continuous with some other, which at a short distance may lie precisely in the same plane. The slight undu- lations, moreover, produced by inequalities on the sides of the hill on which the successive layers were moulded, assists the deception. As countless beds of sand and scoriae constitute the greater part of the whole mass, these may sometimes mantle continuously round the whole cone; and even lava-streams may be of considerable breadth when first they overflow, since in some eruptions a considerable part of the upper portion of the cone breaks down at once, and may form a sheet extending as far as the space which the eye usually takes in in a single section. The high inclination of some of the beds, and the firm union of the particles even where there is evidently no cement, is another striking feature in the volcanic tuffs and breccias, which seems at first not very easy of explanation. But the last great eruption afforded ample illustration of the manner in which these strata are formed. Fragments of lava, scoriae, pumice, and sand, when they fall at slight distances from the summit, are only half cooled down from a state of fusion, and are afterwards acted upon by the heat from within, and by fumeroles or small crevices in the cone through which hot vapours are disengaged. Thus heated, the ejected frag- ments cohere together strongly ; and the whole mass acquires such consistency in a few days, that fragments cannot be detached without a smart blow of the hammer. At the same time sand and scoriae, ejected to a greater distance, remain in- coherent *. * Monticelli and Covelli, Storia di Fenoa, del Vesuv., en 1821-2-3. Ch. XX.] DIKES IN VESUVIUS, HOW FORMED. 393 Dikes in the recent cone, how formed. The inclined strata before mentioned, which dip outwards in all directions from the axis of the cone of Vesuvius, are intersected by veins or dikes of compact lava, for the most part in vertical position. In 1828 these were seen to be about seven in number, some of them not less than four or five hundred feet in height, and thinning out before they reached the uppermost part of the cone. Being harder than the beds through which they pass, they have resisted decomposition, and stand out in relief *. There can be no doubt that these dikes have been produced by the filling up of open fissures with liquid lava ; but of the date of their formation we know nothing further than that they are all subsequent to the year 79, and, relatively speak- ing, that they are more modern than all the lavas and scoriae which they intersect. A considerable number of the upper strata, not traversed by them^ must have been due to later eruptions, if the dikes were filled from below. That the earthquakes which almost invariably precede eruptions occa- sion rents in the mass is well known ; and, in 1822, three months before the lava flowed out, open fissures, evolving hot vapours, were numerous. It is clear that such rents must be injected with melted matter when the column of lava rises, so that the origin of the dikes is easily explained, as also the great solidity and crystalline nature of the rock composing * When I visited Vesuvius in November, 1828, 1 was prevented from descend- ing into the crater by the constant ejections then thrown out. I only got sight of three of the dikes, but Signer Monticelli had previously had drawings made of the whole, which he showed me. The veins which I saw were on that side of the cone which is encircled by Somma. In March of the year before mentioned, an eruption began at the bottom of the deep gulph formed in 1822. The ejected mat- ter had filled up nearly one-third of the original abyss in November, and the same operation was slowly continuing, a single black cone being seen at the bot- tom in almost continual activity. It is clear that these ejections may continue till the throat of Vesuvius is filled up in the same manner as before 1822; and Mr. Scrope has referred the frequent occurrence of volcanic cones without craters to this cause. I found, in 1828, the lava of 1822 not yet cool on the north side of the cone, and evolving much heat and vapour from crevices, 394 SECTION OF VESUVIUS AND SOMMA. [Ch.XX. them, which has been formed by lava cooling down slowly under great pressure. Section through Vesuvius and Somma. In the annexed diagram (No. 13) it will be seen that, on the side of Vesuvius opposite to that where a portion of the ancient cone of Somma (a) still remains, is a projection (6) called the Pedamentina, which some have supposed to be part of the circumference of No. 13. Supposed section of Vesuvius and Somma. a. Monte Somma, or the remains of the ancient cone of Vesuvius. b. The Pedamentina, a terrace-like projection, encircling the base of the recent cone of Vesuvius, on the south side. c. Atrio del Cavallo *. d. e. Crater left by eruption of 1822. f. Small cone thrown up in 1828, at the bottom of the great crater. g. g. Dikes intersecting Somma. h. h. Dikes intersecting the recent cone of Vesuvius. the ancient crater broken down towards the sea, and over the edge of which the lavas of the modern Vesuvius have poured ; the axis of the present cone of Vesuvius being, according to Visconti, precisely equidistant from the escarpment of Somma and the Pedamentina. But it has been objected (and not without reason) to this hypothesis, that if the Pedamentina and the escarpment of Somma were the remains of the original crater, that crater must have been many miles in diameter, and more enormous than almost any one known on the globe. It * So called from travellers leaving their horses and mules there when they pre- pare to ascend the cone on foot. Ch. XX.] SECTION OF VESUVIUS AND SOMMA. 395 is therefore more probable that the ancient mountain was higher than Vesuvius (which, comparatively speaking, is a volcano of no great height), and that the explosions of the year 79 caused it not merely to disgorge the contents of its crater, which had long been choked up, but blew up a great part of the cone itself : so that the wall of Somma, and the ridge or terrace of the Pedamentina, were never the margin of a crater of eruption, but are the relics of a ruined and trun- cated cone. It will be seen in the diagram that the slanting beds of the cone of Vesuvius become horizontal in the Atrio del Cavallo (at c), where the base of the new cone meets the precipitous escarpment of Somma ; for when the lava flows down to this point, as happened in 1822, its descending course is arrested, and it then runs in another direction along this small valley, circling round the base of the cone. Sand and scoriae, also, blown by the winds, collect at the base of the cone, and are then swept away by torrents ; so that there is always here a flattish plain, as represented. In the same man- ner the small interior cone (/) must be composed of sloping beds, terminating in a horizontal plain ; for while this mon- ticule was gradually gaining height by successive ejections of lava and scoriae, in 1828, it was always surrounded by a flat pool of semi-fluid lava, into which scoriae and sand were thrown. The escarpment of Somma exhibits a structure precisely similar to that of the cone of Vesuvius, but the beds are inter- sected by a much greater number of dikes. The formation of this older cone does not belong to the historical era, and we must not therefore enlarge upon it in this place ; but we shall have occasion presently to revert to the subject, when we speak of a favourite doctrine of some modern geologists, concerning 'craters of elevation' (Erhebung's Cratere), whereby, in defi- ance of analogy, the origin of the identical disposition of the strata and dikes in Vesuvius and Somma has been referred to a mode of operation totally dissimilar. Vesuman Lavas. The modern lavas of Vesuvius are cha- 396 VESUVIAN LAVAS. [Ch. XX. racterized by a large proportion of augite (or pyroxene). When they are composed of this mineral and felspar, they may be said to differ in no way in composition from many of the ancient volcanic rocks of Scotland. They are often porphyri- tic, containing disseminated crystals of augite, leucite, or some other mineral, imbedded in a more earthy base. These por- phyritic lavas are often extremely compact, especially in the dikes of Vesuvius and Somma, which, in hardness and specific gravity, are by no means inferior to ordinary veins of trap, and, like them, often preserve a remarkable parallelism in their two opposite faces for considerable distances. In regard to the structure of the Vesuvian lavas on a great scale, there are no sections of sufficient depth to enable us to draw fair comparisons between them and the products of extinct volcanos. At the fortress near Torre del Greco a section is exposed, fifteen feet in height, of a current which ran into the sea ; and it evinces, especially in the ower part, a decided tendency to divide into rude columns. A still more striking example may be seen to the west of Torre del Annun- ziata, near Forte Scassato, where the mass is laid open by the sea to the depth of twenty feet. In both these cases, however, the rock may rather be said to be divided into numerous per- pendicular fissures, than to be prismatic, although the same picturesque effect is produced. In the lava-currents of Central France (those of the Vivarais, in particular), the uppermost portion, often forty feet or more in thickness, is an amorphous mass passing downwards into lava, irregularly prismatic ; and, under this, there is a foundation of regular and vertical columns, in that part of the current which must have cooled most slowly. But the lavas last mentioned are often one hun- dred feet or more in thickness ; and we cannot expect to dis- cover the same phenomenon in the shallow currents of Vesu- vius, although it may be looked for in modern streams in Ice- land, which exceed even those of ancient France in volume. Mr. Scrope * mentions that, in the cliffs encircling the great * Journ, of Sci., vol. xv. p. 177. Ch. XX.] EFFECTS OF DECOMPOSITION ON LAVAS. 397 crater of the modern cone, he saw many currents offering a columnar division, and some almost as regularly prismatic as any ranges of the older basalts ; and he adds, that in some the spheroidal concretionary structure, on a large scale, was equally conspicuous. Brieslak * also informs us that, in the siliceous lava of 1737, which contains augite, leucite, and crystals of felspar, he found very regular prisms in a quarry near Torre del Greco ; which observation is confirmed by modern autho- rities f . Effects of decomposition on lavas. The decomposition of some of the f el spathic lavas, either by simple weathering, or by gaseous emanations, converts them from a hard to a soft clayey state, so that they no longer retain the smallest resem- blance to rocks cooled down from a state of fusion. The ex- halations of sulphuretted hydrogen and muriatic acid which are disengaged continually from the Solfatara, also produce curious changes on the trachyte of that extinct volcano : the rock is whitened and becomes porous, fissile, and honeycombed, till at length it crumbles into a white siliceous powder J. Numerous globular concretions, composed of concentric lami- nae, are also formed by the same vapours in this decomposed rock . They who have visited the Phlegraean Fields and the vol- canic region of Sicily, and who are aware of the many pro- blematical appearances which igneous rocks of the most modern origin assume, especially after decomposition, cannot but be astonished at the confidence with which the contending Nep- tunists and Vulcanists in the last century dogmatized on the igneous or aqueous origin of certain rocks of the remotest anti- quity. Instead of having laboured to acquire an accurate acquaintance with the aspect of known volcanic rocks, and the transmutations which they undergo subsequently to their first * Voy. dans la Campanie, tome i. p. 201. f Mr. Forbes on Mount Vesuvius, Edin. Journ. of Sci., No. xviii., Oct. 1828. J Daubeny on Volcanos, p. 169. Scrope, Geol. Trans., second series, vol. ii. p. 346. 398 VESUVIAN MINERALS. [Ch. XX. consolidation, the adherents of both parties seem either to have considered themselves born with an intuitive knowledge of the effects of volcanic operations, or to have assumed that they required no other analogies than those which a laboratory and furnace might supply. Fesuvian Minerals. A great variety of minerals are found in the lavas of Vesuvius and Somma ; for there are so many common to both, that it is unnecessary to separate them. Augite, leucite, felspar, mica, olivine, and sulphur, are most abundant. It is an extraordinary fact, that, in an area of three square miles round Vesuvius, a greater number of simple mine- rals have been found than in any spot of the same dimensions on the surface of the globe. Hauy only enumerated three hundred and eighty species of simple minerals as known to him, and no less than eighty-two had been found on Vesuvius before the end of the year 1828 *. Many of these are peculiar to that locality. Some mineralogists have conjectured that the greater part of these were not of Vesuvian origin, but thrown up in fragments from some older formation, through which the gaseous explosions burst. But none of the older rocks in Italy or elsewhere, contain such an assemblage of mineral products ; and the hypothesis seems to have been prompted by a disin- clination to admit that, in times so recent in the earth's history, the laboratory of Nature could have been so prolific in the creation of new and rare compounds. Had Vesuvius been a volcano of high antiquity, formed when Nature Wanton' (1 as in her prime, and play'd at will Her virgin fancies, it would have been readily admitted that these, or a much greater variety of substances, had been sublimed in the crevices of lava, just as several new earthy and metallic compounds are known to have been produced by fumeroles, since the eruption of 1822. But some violent. hypothesis must always be resorted to, in order to explain away facts which imply the unimpaired energy of reproductive causes, in our own times. * Monticelli and Covelli, Prodrom, della Mineral, Vesuv. Ch. XX.] FLOWING OF LAVA UNDER WATER. 399 Formation of Tuffs. We have hitherto described the struc- ture of the cone ; but a small part only of the ejected matter remains so near to the volcanic orifice. A large portion of sand and scoriae is borne by the winds and scattered over the sur- rounding plains, or falls into the sea ; and much more is swept down by torrents into the deep, during the intervals, often protracted for many centuries, between eruptions. There, hori- zontal deposits of tufaceous matter become intermixed with sediments of other kinds, and with shells and corals, and, when afterwards raised, form rocks of a mixed character, such as tuffs, peperinos, and volcanic conglomerates. Flowing of lava under water. Some of the lavas, also, of Vesuvius reach the sea, as do those of almost all volcanos ; since they are generally in islands, or bordering the coast. Here they find a bottom already rendered nearly level, for rea- sons before explained by us when speaking of deltas. Instead, therefore, of being highly inclined, as around the cone, or in narrow bands as in a valley, they spread out in broad horizon- tal sheets so long as they retain their fluidity ; and this process may probably continue for a considerable time, since, as upon the land, the upper coating of hardened lava protects the liquid and moving mass below from contact with the air, so beneath the sea the same superficial crust may prevent the great body of lava from cooling, and, being pressed upon by the weight of an increasing column of water as the current descends, it is pro- bably squeezed down : thus the subjacent matter, still in a state of fusion, may be made to flow rapidly towards all points of the compass. , Volcanic alluvions. In addition to the ejections which fall on the cone, and that much greater mass which finds its way gradually to the neighbouring sea, there is a third portion often of no inconsiderable thickness, composed of alluvions, spread over the valleys and plains at small distances from the volcano. Immense volumes of aqueous vapour are evolved from a crater during eruptions, and often for a long time subsequently to the discharge of scoriae and lava. These vapours are condensed in 400 COMPOSITION OF THE MASS ENVELOPING [Ch, XX. the cold atmosphere surrounding the high volcanic peak, and heavy rains are caused sometimes even in countries where, under other circumstances, such a phenomenon is entirely unknown. The floods thus occasioned sweep along the impalpable dust and light scoriae, till a current of mud is produced, which is called, in Campania, * lava d'acqua,' and is often more dreaded than an igneous stream (lava di fuoco), from the greater velo- city with which it moves. So late as the 27th of October, 1822, one of these alii vions descended the cone of Vesuvius. After overspreading much cultivated soil, it flowed suddenly into the villages of St. Sebastian and Massa, and, filling the streets and interior of some of the houses, suffocated seven per- sons. It will therefore happen very frequently, that, towards the base of a volcanic cone, alternations will be found of lava, alluvions, and showers of ashes. Mass enveloping Herculaneum and Pompeii. To which of these two latter divisions the mass enveloping Herculaneum and Pompeii should be referred, has been a question of the keenest controversy ; but the discussion might have been shortened, if the combatants had reflected that, whether volcanic sand and ashes were conveyed to the towns by running water, or through the air, during an eruption, the interior of buildings, so long as the roofs remain entire, together with all underground vaults and cellars, could only be filled by an alluvion. We learn from history, that a heavy shower of sand, pumice, and lapilli, suf- ficiently great to render Pompeii and Herculaneum uninhabit- able, fell for eight successive days and nights, in the year 79, accompanied by violent rains. We ought, therefore, to find a very close resemblance between the strata covering these towns, and those composing the minor cones of the Phlegrasan Fields, accumulated rapidly, like Monte Nuovo, during a continued shower of ejected matter ; with this difference, that the strata incumbent on the cities would be horizontal, whereas those in the cones are highly inclined, and that large angular fragments of rock, which are thrown out near the vent, would be wanting at a distance, where small lapilli only would be found. Accord- - Ch. XX.] IIERCULANEUM AND POMPEII. 401 ingly, with these exceptions, no identity can be more perfect than the form and distribution of the matter at the base of Monte Nuovo, as laid open by the encroaching sea, and the appearance of the beds superimposed on Pompeii. That city is covered with numerous alternations of different horizontal beds of tuff and lapilli, for the most part thin, and subdivided into very fine layers. I observed the following section near the Amphitheatre, in November, 1828 (descending series). Feet, Inches. 1. Black sparkling sand from the eruption of 1822, containing minute regularly-formed crystals of augite and tourmaline from . . , 2 to 3* 2. Vegetable mould 30 3. Brown incoherent tuff full of pisolitic globules in layers, from half an inch to three inches in thickness . 16 4. Small scoriae and white lapilli . . . . .03 5. Brown earthy tuff with numerous pisolitic globules . 9 6. Brown earthy tuff with lapilli divided into layers . .40 7. Layer of whitish lapilli 01 8. Grey solid tuff 03 9. Pumice and white lapilli ..... 03 10 4 Many of the ashes in these beds are vitrified and harsh to the touch. Crystals of leucite, both fresh and farinaceous, have been found intermixed f. The depth of the bed of ashes above the houses is variable, but seldom exceeds twelve our fourteen feet, and it is said that the higher part of the Amphitheatre always projected above the surface ; though, if this were the case, it seems to be inexplicable that the city should never have been discovered till the year 1750. It will be observed, in the above section, that two of the brown half-consolidated tuffs are filled with small pisolitic globules. It is surprising that this * The last great eniption, in 1822, only caused a covering of a few inches thick on Pompeii. Several feet are mentioned by Mr. Forbes. Ed. Journ. of Science, No. xix. p. 131, Jan. 1829. But he must have measured in spots where it had drifted. The dust and ashes were five feet thick at the top of the crater, and decreased gradually to ten inches at Torre del Annunziata. The size and weight of the ejected fragments diminished very regularly in the same continuous Stratum as the distance from the centre of projection was greater. f Forbes, Ed. Journ. of Sci., No. xix. p. 130, Jan. 1829. VOL. I. 2 D 402 COMPOSITION OF THE MASS ENVELOPING [Ch. XX- circumstance is not alluded to in the animated controversy which the Royal Academy of Naples maintained with one of their members, Signor Lippi, as to the origin of the strata incumbent on Pompeii. The mode of aggregation of these globules has been fully explained by Mr. Scrope, who saw them formed in great numbers, in 1822, by rain falling during the eruption on fine volcanic sand, and sometimes, also, beheld them produced like hail in the air, by the mutual attraction of the minutest particles of fine damp sand. Their occurrence, therefore, agrees remarkably well with the account of heavy rain, and showers of sand and ashes, recorded in history, and is opposed to the theory of an alluvion brought from a distance by a flood of water. Controversy as to the destruction of Her culaneum and Pom- peii. Lippi entitled his work ' Fu il fuoco o 1' acqua che sotterrd Pompei ed Ercolano * ? ' and he contended that neither were the two cities destroyed in the year 79, nor by a volcanic eruption, but purely by the agency of water charged with transported matter. His Letters, wherein he endeavoured to dispense, as far as possible, with igneous agency, even at the foot of the volcano, were dedicated, with great propriety, to Werner, and aiford an amusing illustration of the polemic style in which geological writers of that day indulged themselves. His arguments were partly of an historical nature, derived from the silence of contemporary historians, respecting the fate of the cities which, as we have already stated, is most remarkable 3 and were partly drawn from physical proofs. He pointed out with great clearness the resemblance of the tufaceous matter in the vaults and cellars at Herculaneum and Pompeii to aqueous alluvions, and its distinctness from ejections which had fallen through the air. Nothing, he observed, but moist pasty matter could have received the impression of a woman's breast, which was found in a vault at Pompeii, or have given the cast of a statue discovered in the theatre at Herculaneum. It was ob- jected to him, that the heat of the tuff in Herculaneum and * Napoli, 1816. Ch. XX.] HERCULANEUH AND POMPEII. 403 Pompeii was proved by the carbonization of the timber, corn, papyrus-rolls, and other vegetable substances there discovered : but Lippi replied with truth, that the papyri would have been burnt up, if they had come in contact with fire, and that their being only carbonized, was a clear demonstration of their hav- ing been enveloped, like fossil wood, in a sediment deposited from water. The Academicians, in their report on his pamphlet, assert, that when the Amphitheatre was first cleared out, the matter was arranged, on the steps, in a succession of concave ayers, accommodating themselves to the interior form of the >uilding, just as snow would lie if it had fallen there. This >bservation is highly interesting, and points to the difference )etween the stratification of ashes in an open building, and of mud derived from the same in the interior of edifices and cellars. SOT ought we to call the allegation in question, because it could not be substantiated at the time of the controversy, when the matter was all removed ; although Lippi took advantage of this removal, and met the argument of his antagonists by re- quiring them to prove the fact. Pompeii not destroyed by lava. There is decisive evidence that no stream of lava has ever reached Pompeii since it was first built, although the foundations of the town stand upon the old leucitic lava of Somma ; several of whose streams, with uff interposed, have been cut through in excavations. At ELerculaneum the case is different, although the substance which fills the interior of the houses and the vaults must have Deen introduced in a state of mud, like that found in similar iituations in Pompeii: yet the superincumbent mass differs vholly in composition and thickness. Herculaneum was situ- ated several miles nearer to the volcano, and has, therefore, >een always more exposed to be covered, not only by showers of ashes, but by alluvions and streams of lava. Accord- ngly, masses of both have accumulated on each other above the city, to a depth of nowhere less than seventy, and in many places of one hundred and twelve feet *. * Hamilton's Observations on Mount Vesuvius, p. 94, London, 1774, 2 D 2 404 DEJECTS PRESERVED IN [Ch. XX. The tuff which envelops the buildings consists of commi- nuted volcanic ashes, mixed with pumice. A mask imbedded in this matrix has left a cast, the sharpness of which was com- pared by Hamilton to those in Paris plaster ; nor was the mask in the least degree scorched, as we might expect it to have been, if it had been imbedded in heated matter. This tuff is porous, and, when first excavated, is soft and easily worked, but acquires a considerable degree of induration on exposure to the air. Above this lowest stratum is placed, according to Hamilton, ' the matter of six eruptions,' each separated from the other by veins of good soil. In these soils Lippi informs us, that he collected a considerable number of land shells an observation which is no doubt correct, for we know that in Italy several species burrow annually, in certain seasons, to the depth of five feet and more from the surface. Delia Torre also informs us that there is in one part of this superimposed mass a bed of true siliceous lava (lava di pietra dura) and, as no such current is believed to have flowed till near one thousand years after the destruction of Herculaneum, we must conclude, that the origin of a large part of the cover- ing of Herculaneum was long subsequent to the first inhuma- tion of the place. That city, as well as Pompeii, was a sea- port. Herculaneum is still very near the shore, but a tract of land, a mile in length, intervenes between the borders of the Bay of Naples and Pompeii. In both cases the gain of land is due to the filling up of the bed of the sea with volcanic mat- ter, and not to elevation by earthquakes, for there has been no change in the relative level of land and sea. Pompeii stood on a slight eminence composed of the lavas of the ancient Vesuvius, and flights of steps led down to the water's edge. The lowermost of these steps are said to be still on an exact level with the sea. Condition and contents of the buried cities. After these observations on the nature of the strata enveloping and sur- rounding the cities, we may proceed to consider their internal condition and contents, so far at least as they offer facts of Ch.XX.] HERCULANEUM AND POMPEII. 405 geological interest. Notwithstanding the much greater depth at which Herculaneum was buried, it was discovered before Pompeii, by the accidental circumstance of a well being sunk, in 1713, which came right down upon the theatre, where the statues of Hercules and Cleopatra were soon found. Whether this city or Pompeii, both of them founded by Greek colonies, was the most considerable, is not yet determined ; but both are mentioned by ancient authors as among the seven most flourishing cities in Campania. The walls of Pompeii were three miles in circumference; but we have, as yet, no certain knowledge of the dimensions of Herculaneum. In the latter place the theatre alone is open for inspection ; the Forum, Temple of Jupiter, and other buildings, having been filled up with rubbish as the workmen proceeded, owing to the difficulty of removing it from so great a depth below ground. Even the theatre is only seen by torch-light, and the most interesting information, perhaps, which the geologist obtains there, is the continual formation of stalactite in the galleries cut through the tuff ; for there is a constant percolation of water charged with carbonate of lime mixed with a small portion of magnesia. Such mineral waters must, in the course of time, create great changes in many rocks : and we cannot but perceive the un- reasonableness of the expectations of some geologists, that vol- canic rocks of remote eras should accord precisely with those of modern date ; since it is obvious that many of those pro- duced in our own time will not long retain the same aspect and composition. Both at Herculaneum and Pompeii, temples have been found with inscriptions commemorating their having been rebuilt after they were thrown down by an earthquake *. This earthquake happened in the reign of Nero, sixteen years before the inhumation of the cities. In Pompeii, one-fourth of which is now laid open to the day, both the public and pri- vate buildings bear testimony to the catastrophe. The walls are rent, and in many places traversed by fissures still open. * Swinburne and Lalande Paderni, Phil. Trans. 1758, vol. 50, p. 619. 406 OBJECTS PRESERVED IN [Ch. XX. Columns are lying on the ground only half hewn from huge blocks of travertin, and the temple for which they were designed is seen half repaired. In some few places the pavement had sunk in, but in general it was undisturbed, consisting of great flags of lava, in which two immense ruts have been worn by the constant passage of carriages through the narrow street. When the hardness of the stone is considered, the continuity of these ruts from one end of the town to the other is not a little remarkable, for there is nothing of the kind in the oldest pavements of modern cities. Small number of skeletons. A very small number of skele- tons have been discovered in either city ; and it is clear that the great mass of inhabitants not only found time to escape, but also to carry with them the principal part of their valuable effects. In the barracks at Pompeii were the skeletons of two soldiers chained to the stocks, and in the vaults of a country- house in the suburbs, were the skeletons of seventeen persons who appear to have fled there to escape from the shower of ashes. They were found inclosed in an indurated tuff, and in this matrix was preserved a perfect cast of a woman, perhaps the mistress of the house, with an infant in her arms. Although her form was imprinted on the rock, nothing but the bones remained. To these a chain of gold was suspended, and rings with jewels were on the lingers of the skeleton. Against the sides of the same vault was ranged a long line of earthen amphorae. The writings scribbled by the soldiers on the walls of their barracks, and the names of the owners of each house written over the doors, are still perfectly legible. The colours of fresco paintings on the stuccoed walls in the interior of buildings are almost as vivid as if they were just finished. There are public fountains decorated with shells laid out in patterns in the same fashion as those now seen in the town of Naples ; and in the room of a painter who was perhaps a naturalist, a large col- lection of shells was found comprising a great variety of Medi- terranean species, in as good a state of preservation as if they Ch. XX.] HERCULANEUM AND POMPEII. 407 had remained for the same number of years in a museum. A comparison of these remains with those found so generally in a fossil state would not assist us in obtaining the least insight into the time required to produce a certain degree of decompo- sition or mineralization ; for although, under favourable cir- cumstances, much greater alteration might doubtless have been brought about in a shorter period, yet the example before us shows that an inhumation of seventeen centuries may sometimes effect nothing towards the reduction of shells and several other bodies to the state in which fossils are usually found. The wooden beams in the houses at Herculaneum are black on the exterior, but when cleft open they appear to be almost in the state of ordinary wood, and the progress made by the whole mass towards the state of lignite is scarcely appreciable. Some animal and vegetable substances of more perishable kinds have of course suffered much change and decay, yet the state of conservation of these is truly remarkable. Fishing-nets are very abundant in both cities, often quite entire ; and their number at Pompeii is the more interesting from the sea being now, as we stated, a mile distant. Linen has been found at Herculaneum, with the texture well defined ; and in a fruit- erer's shop in that city were discovered vessels full of almonds, chestnuts, walnuts, and fruit of the ' carubiere,' all distinctly recognizable from their shape. A loaf, also, still retaining its form, was found in a baker's shop, with his name stamped upon it thus: * Eleris Q. Crani Riser/ On the counter of an apothecary was a box of pills converted into a fine earthy sub- stance ; and by the side of it a small cylindrical roll, evidently prepared to be cut into pills. By the side of these was a jar containing medicinal herbs. In 1827, moist olives were found in a square glass case, and ' caviare,' or roe of a fish, in a state of wonderful preservation. An examination of these curious condiments has been published by Covelli, of Naples, and they are preserved hermetically sealed in the museum there *. * Mr. Forbes, Edin. Journ. of ScL, No. xix. p. 130, Jan., 1829. 408 PAPVRI IN HERCULANEUM. [Ch. XX. Papyri. There is a marked difference in the condition and appearance of the animal and vegetable substances found in Pom- peii and Herculaneum ; those of Pompeii being penetrated by a gray pulverulent tuff, those in Herculaneum seeming to have been first enveloped by a paste which consolidated round them, and then allowed them to become slowly carbonized. Some of the rolls of papyrus at Pompeii still retain their form; but the writing, and indeed almost all the vegetable matter, appear to have vanished and to have been replaced by volcanic tufa some- what pulverulent. At Herculaneum the earthy matter has scarcely ever penetrated ; and the vegetable substance of the papyrus has become a thin friable black matter, almost resem- bling in appearance the tinder which remains when stiff paper has been burnt, in which the letters may still be sometimes traced. The small bundles of papyri, composed of five or six rolls tied up together, had sometimes lain horizontally, and were pressed in that direction, but sometimes they had been placed in a vertical position. Small tickets were attached to each bundle,, on which the title of the work was inscribed. In one case only have the sheets been found with writing on both sides of the pages. So numerous are the obliterations and cor- rections, that many must have been original manuscripts. The variety of hand-writings is quite extraordinary : almost all are written in Greek, but there are a few in Latin. They were all found in the library of one private individual; and the titles of four hundred of those least injured, which have been read, are found to be unimportant works, but all entirely new, chiefly relating to music, rhetoric, and cookery. There are two vo- lumes of Epicurus ' On Nature/ and the others are mostly by writers of the same school, only one fragment having been dis- covered, by an opponent of the Epicurean system, Crisippus*. * In one of the manuscripts which was in the hands of the interpreters when I visited the museum, the author indulges in the speculation that all the Homeric personages were allegorical that Agamemnon was the ether, Achilles the sun, Helen the earth, Paris the air, Hector the moon, &c. Ch. XX.] PAPYRI IN HERCULANEUM. 409 In the opinion of some antiquaries, not one-hundredth part of the city has yet been explored ; and the quarters hitherto cleared out, at great expense, are those where there was the least probability of discovering manuscripts. Probability of future discoveries of MSS. As Italy could already boast splendid Roman amphitheatres and Greek tem- ples, it was a matter of secondary interest to add to their number those in the dark and dripping galleries of Hercu- laneum ; and having so many of the masterpieces of ancient art, we could have dispensed with the inferior busts and statues which could alone have been expected to reward our researches in the ruins of a provincial town. But from the moment that it was ascertained that rolls of papyrus preserved in this city could still be decyphered, every exertion ought to have been steadily and exclusively directed towards the dis- covery of other libraries. Private dwellings should have been searched, and no labour and expense should have been consumed in examining public edifices. A small portion of that zeal and enlightened spirit which prompted the late French and Tuscan expedition to Egypt, might, long ere this, in a country nearer home, have snatched from oblivion some of the lost works of the Augustan age, or of most of the eminent Greek historians and philosophers. A single roll of papyrus might have dis- closed more matter of intense interest than all that was ever written in hieroglyphics *. Stabia. Besides the cities already mentioned, Stabiae, a small town abcut six miles from Vesuvius, and near the site of the modern Castel-a-Mare (see map, plate 2), was over- whelmed during the eruption of 79. Pliny mentions that, * During ray stay at Naples, in 1828, the Neapolitan Government, after having discontinued operations for many years, cleared out a small portion of Hercula- neum, near the sea, where the covering was least thick. After this expense had been incurred, it was discovered that the whole of the ground had been previously examined, near a century before, by the French Prince d'Elbeuf, who had removed everything of value ! The want of system with which operations have always been, and still are, carried on is such, that we may expect similar blunders to be made continually. 410 DESTRUCTION OF TORRE DEL GRECO. [Chap, XX. when his uncle was there, he was obliged to make his escape, so great was the quantity of falling stones and ashes. In the ruins of this place, a few skeletons have been found buried in volcanic ejections, together with some antiquities of no great value, and rolls of papyrus, which, like those of Pompeii, were illegible. Torre del Greco overflowed by lava.- Of the towns hitherto mentioned, Herculaneum alone has been overflowed by a stream of melted matter ; but this did not, as we have seen, enter or injure the buildings which were previously enveloped or co- vered over with tuff. But burning torrents have often taken their course through the streets of Torre del Greco, and con- sumed or inclosed a large portion of the town in solid rock. It seems probable that the destruction of three thousand of its in- habitants, in 1631, which some accounts attribute to boiling water, was principally due to one of those alluvions which we before mentioned ; but, in 1737, the lava itself flowed through the eastern side of the town, and afterwards reached the sea : and, in 1794, another current rolling over the western side, filled the streets and houses, and killed more than four hundred persons. The main street is now quarried through this lava, which supplied building-stones for new houses erected where others had been annihilated. The church was half buried in a rocky mass, but the upper portion served as the foun- dation of a new edifice. The number of the population at present is estimated at fifteen thousand ; and a satisfactory answer may readily be re- turned to those who inquire how the inhabitants can be so e inattentive to the voice of time and the warnings of Nature *,' as to rebuild their dwellings on a spot so often devastated. No neighbouring site unoccupied by a town, or which would not be equally insecure, combines the same advantages of proximity to the capital, to the sea, and to the rich lands on the flanks of Vesuvius. If the present population were exiled, they would * Sir H. Davy, Consolations in Travel, p. 66. Ch. XX.] REFLECTIONS ON THE BURIED CITIES. 411 immediately be replaced by another, for the same reason that the Maremma of Tuscany and the Campagna di Roma will never be depopulated, although the malaria fever commits more havoc in a few years than the Vesuvian lavas in as many cen- turies. The district around Naples supplies one, amongst innu- merable examples, that those regions where the surface is most frequently renewed, and where the renovation is accompanied, at different intervals of time, by partial destruction of animal and vegetable life, may nevertheless be amongst the most habit- able and delightful on our globe. We have already made a similar remark when speaking of tracts where aqueous causes are now most active; and the ob- servation applies as well to parts of the surface which are the abode of aquatic animals, as to those which support terrestrial species. The sloping sides of Vesuvius give nourishment to a vigorous and healthy population of about eighty thousand souls ; and the surrounding hills and plains, together with several of the adjoining isles, owe the fertility of their soil to matter ejected by prior eruptions. Had the fundamental lime- stone of the Apennines remained uncovered throughout the whole area, the country could not have sustained a twentieth part of its present inhabitants. This will be apparent to every geologist who has marked the change in the agricultural cha- racter of the soil the moment he has passed the utmost boundary of the volcanic ejections, as when, for example, at the distance of about seven miles from Vesuvius, he leaves the plain and ascends the declivity of the Sorrentine Hills. Concluding remarks on the destroying and renovating agency of the Campanian volcanos. Yet favoured as this region has been by Nature from time immemorial, the signs of the changes imprinted on it during the period that it has served as the habitation of man, may appear in after-ages to indicate a series of unparalleled disasters. Let us suppose that at some future time the Mediterranean should form a gulf of the great ocean, and that the tidal current should encroach on the shores of Campania, as it now advances upon the eastern coast of Eng- 412 REFLECTIONS ON THE BURIED CITIES. [Ch. XX. land: the geologist will then behold the towns already buried, and many more which will evidently be entombed hereafter, laid open in the steep cliffs, where he will discover buildings superimposed above each other, with thick intervening strata of tuff or lava some unscathed by fire, like those of Hercu- laneum and Pompeii, others half melted down, as in Torre del Greco, and many shattered and thrown about in strange con- fusion, as in Tripergola. Among the ruins will be seen skele- tons of men, and impressions of the human form stamped in solid rocks of tuff. Nor will the signs of earthquakes be want- ing. The pavement of part of the Domitian Way, and the Temple of the Nymphs, submerged at high tide, will be unco- vered at low water, the columns remaining erect and uninjured. Other temples which had once sunk down, like that of Serapis, will be found to have been upraised again by subsequent move- ments. If they who study these phenomena, and speculate on their causes, assume that there were periods when the laws of Nature differed from those established in their own time, they will scarcely hesitate to refer the wonderful monuments in question to those primeval ages. When they consider the nu- merous proofs of reiterated catastrophes to which the region was subject, they may, perhaps, commiserate the unhappy fate of beings condemned to inhabit a planet during its nascent and chaotic state, and feel grateful that their favoured race escaped such scenes of anarchy and misrule. Yet what was the real condition of Campania during those years of dire convulsion ? ' A climate where heaven's breath smells sweet and wooingly a vigorous and luxuriant nature unparalleled in its productions a coast which was once the fairy land of poets, and the favourite retreat of great men. Even the tyrants of the creation loved this alluring region, spared it, adorned it, lived in it, died in it*.' The inha- bitants, indeed, have enjoyed no immunity from the calamities which are the lot of mankind ; but the principal evils which they have suffered must be attributed to moral, not to phy- * Forsyth's Italy, vol. ii. Ch. XX.] REFLECTIONS ON THE BURIED CITIES. 413 sical causes to disastrous events over which man might have exercised a control, rather than to the inevitable catastrophes which result from subterranean agency. When Spartacus en- camped his army of ten thousand gladiators in the old extinct crater of Vesuvius, the volcano was more justly a subject of terror to Campania, than it has ever been since the rekindling of its fires. CHAPTER XXI. External physiognomy of Etna Minor cones produced by lateral eruptions Suc- cessive obliteration of these cones Early eruptions of Etna Monti Rossi thrown up in 1669 Great fissure of S. Lio Towns overflowed by lava. Part of Catania destroyed Mode of the advance of a current of lava Excavation of a church under lava Series of subterranean caverns Linear direction of cones formed in 1811 and 1819 Flood produced in 1755 by the melting of snow during an eruption A glacier covered by a lava-stream on Etna Vol- canic eruptions in Iceland New island thrown up in 1783 Two lava currents of Skaptar Jokul in the same year Their immense volume Eruption of Jo- rullo in Mexico Humboldt's Theory respecting the convexity of the Plain of Malpais. ETNA. External physiognomy of the cone. As we have entered into a detailed historical account of the changes in the volcanic district round Naples, our limits will only permit us to allude in a cursory manner to some of the circumstances of principal interest in the history of other volcanic mountains. After Vesuvius, our most authentic records relate to Etna, which rises near the sea in solitary grandeur to the height of nearly eleven thousand feet *, the mass being chiefly composed of volcanic matter ejected above the surface of the water. The base of the cone is almost circular, and eighty-seven English miles in circumference ; but if we include the whole district over which its lavas extend, the circuit is probably twice that extent. Divided into three regions. The cone is divided by Nature into three distinct zones, called the fertile, the woody, and the desert regions. The first of these, comprising the delightful country around the skirts of the mountain, is well cultivated, thickly inhabited, and covered with olives, vines, corn, fruit- trees, and aromatic herbs. Higher up, the woody region * According to Captain Smyth (Sicily and its Islands, p. 145), ita height is 10,874 feet. Ch. XXI.] MINOR VOLCANOS ON ETNA. 415 encircles the mountain an extensive forest, six or seven miles in width, affording pasturage for numerous flocks. The trees are of various species, the chestnut, oak, and pine being most luxuriant ; while, in some tracts, are groves of cork and beech. Above the forest is the desert region, a waste of black lava and scoriae ; where,, on a kind of plain, rises the cone to the height of about eleven hundred feet, from which sulphureous vapours are continually evolved. The most grand and original feature in the physiognomy of Etna is the multitude of minor cones which are distributed over its flanks, and which are most abun- dant in the woody region. These, although they appear but trifling irregularities when viewed from a distance as subordi- nate parts of so imposing and colossal a mountain, would, never- theless, be deemed hills of considerable altitude in almost any other region. Cones produced by lateral eruptions. Without enumerating numerous monticules of ashes thrown out at different points, there are about eighty of these secondary volcanos, of consi- derable dimensions ; fifty- two on the west and north, and twenty-seven on the east side of Etna. One of the largest, called Monte Minardo, near Bronte, is upwards of seven hun- dred feet in height ; and a double hill near Nicolosi, called Monti Rossi, formed in 1669, is four hundred and fifty feet high, and the base two miles in circumference ; so that it somewhat exceeds in size Monte Nuovo, before described. Yet it ranks only as a cone of the second magnitude amongst those produced by the lateral eruptions of Etna. On looking down from the lower borders of the desert region, these vol- canos present us with one of the most beautiful and charac- teristic scenes in Europe. They afford every variety of height and size, and are arranged in beautiful and picturesque groups. However uniform they may appear when seen from the sea, or the plains below, nothing can be more diversified than their shape when we look from above into their craters, one side of which is generally broken down. There are, indeed, few objects in Nature more picturesque than a wooded vol- 416 BURIED CONES ON ETNA. [Ch. XXI. canic crater. The cones situated in the higher parts of the forest zone are chiefly clothed with lofty pines ; while those at a lower elevation are adorned with chestnuts, oak, beech, and holm. Successive obliteration of these cones. The history of the eruptions of Etna, imperfect and interrupted as it is, affords, nevertheless, a full insight into the manner in which the whole mountain has successively attained its present magnitude and internal structure. The principal cone has more than once fallen in and been reproduced. In 1444 it was three hundred and twenty feet high, and fell in after the earthquakes of 1537. In the year 1693, when a violent earthquake shook the whole of Sicily, and killed sixty thousand persons, the cone lost so much of its height, says Boccone, that it could not be seen from several places in Valdemone, whence it was before visible. The greater number of eruptions happen either from the great crater, or from lateral openings in the desert region. When hills are thrown up in the middle zone, and project beyond the general level, they gradually lose their height during subse- quent eruptions ; for when lava runs down from the upper parts of the mountain, and encounters any of these hills, the stream is divided, and flows round them so as to elevate the gently-sloping grounds from which they rise. In this manner a deduction is often made at once of twenty or thirty feet, or even more, from their height. Thus, one of the minor cones, called Monte Peluso, was diminished in altitude by a great lava-stream which encircled it in 1444 ; and another current has recently taken the same course yet this hill still remains four or five hundred feet high. There is a cone called Monte Nucilla, near Nicolosi, round the base of which several successive currents have flowed, and showers of ashes have fallen, since the time of history, till at last, during an eruption in 1536, the surrounding plain was so raised, that the top of the cone alone was left projecting above the general level. Monte Nero, situated above the Grotta dell' Capre, was in 1766 almost submerged by a cur- Ch. XXI.] EARLY ERUPTIONS OF ETNA. 417 rent; and Monte Capreolo afforded, in the year 1669, a curious example of one of the last stages of obliteration : for a lava-stream, descending on a high ridge which had been built up by the continued superposition of successive lavas, flowed directly into the crater, and nearly filled it. The lava, there- fore, of each new lateral cone tends to detract from the relative height of lower cones above their base : so that the flanks of Etna, sloping with a gentle inclination, envelop in succession a great multitude of minor volcanos, while new ones spring up from time to time ; and this has given to the older parts of the mountain, as seen in some sections two or three thousand feet perpendicular, a complex and highly interesting internal structure. Early eruptions of Etna. Etna appears to have been in activity from the earliest times of tradition ; for Diodorus Siculus mentions an eruption which caused a district to be deserted by the Sicani before the Trojan war. Thucydides informs us*, that between the colonization of Sicily by the Greeks, and the commencement of the Peloponnesian war in the year 431 B.C., three eruptions had occurred. The last of these happened in the year 427 B.C., and ravaged the environs of Catania ; and was probably that so poetically described by Pindar in his first Pythian ode. Eruption of 1669 Monti Rossi formed. The great erup- tion which happened in the year 1669 is the first to which we shall call the reader's attention. An earthquake had levelled to the ground all the houses in Nicolosi, a town situated near the lower margin of the woody region, about twenty miles from the summit of Etna, and ten from the sea at Catania. Two gulphs then opened near that town, from whence sand and scoriae were thrown up in such quantity, that, in the course of three or four months, a double cone was formed, called Monti Rossi, about four hundred and fifty feet high. But the most extraordinary phenomenon occurred at the commencement of the convulsion in the plain of S. Lio. A fissure six feet broad, * Book iii., towards the end. VOL. I. 2 E 418 ERUPTION OF ETNA A.D. 16G9 Minor cones on the Jlanks of Etna. 1. Monti Rossi, near Nicolosi, formed in 1669. 2. Vampeluso?* and of unknown depth, opened with a loud crash, and ran in a somewhat tortuous course to within a mile of the summit of Etna. Its direction was from north to south, and its length twelve miles. It emitted a most vivid light. Five other parallel fissures of considerable length afterwards opened one after the other, and emitted smoke, and gave out bellowing sounds which were heard at the distance of forty miles. This case seems to present the geologist with an illustration of the manner in which those continuous dikes of vertical porphyry were formed which are seen to traverse some of the older lavas of Etna ; for the light emitted from the great rent of S. Lio appears to indicate that it was filled to a certain height with incandescent lava, probably to the height of an orifice not far distant from Monti Rossi, which at that time opened and poured out a lava current. The lava current to which we allude soon reached in its course a minor cone called. Mompi- liere, at the base of which it entered a subterranean grotto, communicating with a suite of those caverns which are so com- mon in the lavas of Etna. Here it appears to have melted down some of the vaulted foundations of the hill, so that the * The hill which I have here introduced was called by my guide Vampolara, but the name given in the text is the nearest to this which I find in Gemmellaro's Catalogue of Minor Cones. Ch. XXL] ERUPTION OF ETNA A. D. 1GG9. 419 whole of that cone became slightly depressed and traversed by numerous open fissures. Part of Catania destroyed. The lava, after overflowing fourteen towns and villages, some having a population of be- tween three and four thousand inhabitants, arrived at length at the walls of Catania, hes e had been purposely raised to pro- tect the city ; but the burning flood accumulated till it rose to the top of the rampart, which was sixty feet in height, and then it fell in a fiery cascade and overwhelmed part of the city. The wall, however, was not thrown down, but was discovered long afterwards by excavations made in the rock by the Prince of Biscari ; so that the traveller may now see the solid lava curling over the top of the rampart as if still in the very act of falling. This great current had performed a course of fifteen miles before it entered the sea, where it was still six hundred yards broad and forty feet deep. It covered some territories in the environs of Catania, which had never before been visited by the lavas of Etna. While moving on, its surface was in general a mass of solid rock ; and its mode of advancing, as is usual with lava- streams, was by the occasional fissuring of the solid walls. A gentleman of Catania, named Pappalardo, desiring to secure the city from the approach of the threatening torrent, went out with a party of fifty men whom he had dressed in skins to pro- tect them from the heat, and armed with iron crows and hooks. They broke open one of the solid walls which flanked the cur- rent near Belpasso, and immediately forth issued a rivulet of melted matter which took the direction of Paterno ; but the inhabitants of that town, being alarmed for their safety, took up arms, and put a stop to farther operations*. As another illustration of the solidity of the walls of an advancing lava- stream, we may mention an adventure related by Recupero, who, in 1766, had ascended a small hill formed of ancient volcanic matter, to behold the slow and gradual ap- proach of a fiery current, two miles and a half broad ; w hen suddenly two small threads of liquid matter issuing from a * Ferrara, Descriz. dell' Etna, p. 108. 2 E 2 420 SUBTERRANEAN CAVERNS ON ETNA. [Ch. XXI. crevice detached themselves from the main stream, and ran rapidly towards the hill. He and his guide had just time to escape, when they saw the hill, which was fifty feet in height, surrounded, and in a quarter of an hour melted down into the burning mass, so as to flow on with it. But it must not be supposed that this complete fusion of rocky matter coming in contact with lava is of universal, or even common occurrence. It probably happens when fresh portions of incandescent matter come successively in contact with fusible materials. In many of the dikes which intersect the tuffs and lavas of Etna, there is scarcely any perceptible alteration effected by heat on the edges of the horizontal beds, in contact with the vertical and more crystalline mass. On the site of Mompiliere, one of the towns overflowed in the great eruption above described, an excavation was made in 1704 ; and by immense labour the workmen reached, at the depth of thirty-five feet, the gate of the principal church, where there were three statues, held in high veneration. One of these, together with a bell, some money, and other articles, were extracted in a good state of preservation from beneath a great arch formed by the lava. It seems very extraordinary that any works of art, not encased with tuff, like those in Hercula- neum, should have escaped fusion in hollow spaces left open in this lava-current, which was so hot at Catania eight years after it entered the town, that it was impossible to hold the hand in some of the crevices. Subterranean caverns on Etna. We mentioned the entrance of the lava-stream into a subterranean grotto, whereby the foundations of a hill were partially undermined. Such under- ground passages are among the most curious features on Etna, and appear to have been produced by the hardening of the lava, during the escape of great volumes of elastic fluids, which are often discharged for many days in succession, after the crisis of the eruption is over. Near Nicolosi, not far from Monti Rossi, one of these great openings may be seen, called the Fossa della Palomba, 625 feet in circumference at its mouth, Ch. XXI.] ERUPTIONS OF ETNA IN 1811 AND 1819. 421 and seventy-eight deep. After reaching the bottom of this, we enter another dark cavity, and then others in succession, sometimes descending precipices by means of ladders. At length the vaults terminate in a great gallery ninety feet long, and from fifteen to fifty broad, beyond which there is still a passage, never yet explored; so that the extent of these caverns remains unknown *. The walls and roofs of these great vaults are composed of rough and bristling scoriaB, of the most fan- tastic forms. Eruption of 1811. We shall now proceed to offer some observations on the two last eruptions in 1811 and 1819. It appears, from the relation of Signer Gemmellaro, who wit- nessed the phenomena, that the great crater in 1811 testified, by its violent detonations, that the lava had ascended to near the summit of the mountain, by its central duct. A violent shock was then felt, and a stream broke out from the side of the cone, at no great distance from its apex. Shortly after this had ceased to flow, a second stream burst forth at another opening, considerably below the first ; then a third still lower, and so on till seven different issues had been thus succes- sively formed, all lying upon the same straight line. It has been supposed that this line was a perpendicular rent in the internal framework of the mountain, which rent was probably not produced at one shock, but prolonged successively down- wards, by the lateral pressure and intense heat of the internal column of lava, as it subsided by gradual discharge through each vent f. Eruption c/1819. In 1819 three large mouths or caverns opened very near those which were formed in the eruptions of 1811, from which flames, red hot cinders, and sand, were thrown up with loud explosions. A few minutes afterwards another mouth opened below, from which flames and smoke issued ; and finally a fifth, lower still, whence a torrent of lava flowed, which spread itself with great velocity over the valley * Ferrara, Descriz, dell' Etna. Palermo, 1818. f Scrope on Volcanos, p. 153. 422 MODE OF ADVANCE OF A LAVA-CURRENT. [th. XXI. f del Bove.' This stream flowed two miles in the first twenty- four hours, and nearly as far in the succeeding day and night. The three original mouths at length united into one large crater, and sent forth lava, as did the four inferior apertures, so that an enormous torrent poured down the great valley ' del Bove.' When it arrived at a vast and almost perpendi- cular precipice, at the head of the valley of Calanna, it poured over in a cascade, and, being hardened in its descent, made an inconceivable crash as it was dashed against the bottom. So immense was the column of dust raised by the abrasion of the tufaceous hill over which the hardened mass descended, that the Catanians were in great alarm, supposing a new eruption to have burst out in the woody region, exceeding in violence that near the summit of Etna. Mode of advance of the lava. Of the cones thrown up during this eruption, not more than two are of sufficient mag- nitude to be numbered among those eighty which we before reckoned as adorning the flanks of Etna. The surface of the lava which deluged the valley ' del Bove' consists of rocky and angular blocks, tossed together in the utmost dis- order. Nothing can be more rugged, or more unlike the smooth and even superficies which those who are unacquainted with volcanic countries may have pictured to themselves, in a mass of matter which had consolidated from a liquid state. Mr. Scrope observed this current in the year 1819, slowly progressing down a considerable slope, at the rate of about a yard an hour, nine months after its first emission. The lower stratum being arrested by the resistance of the ground, the upper or central part gradually protruded itself, and being unsupported fell down. This in its turn was covered by a mass of more liquid lava, which swelled over it from above. The current had all the appearance of a huge heap of rough and large cinders rolling over and over upon itself by the effect of an extremely slow propulsion from behind. The contraction of the crust as it solidified, and the friction of the scoriform cakes against one another, produced a crackling Ch. XXL] FLOODS ON ETNA. 423 sound. Within the crevices a dull red heat might be seen by night, and vapour issuing in considerable quantity was visible by day *. Flood produced by the melting of snow by lava. The erosive and transporting power of running water is rarely ex- erted on Etna with great force, the rain which falls being immediately imbibed by the porous lavas ; so that, vast as is the extent of the mountain, it feeds only a few small rivu- lets, and these, even, are dry throughout the greater portion of the year. The enormous rounded boulders, therefore, of trachyte and basalt, a line of which can be traced from the sea, from near Giardini, by Mascali, and Zafarana, to the valley f del Bove, J would offer a perplexing problem to the geo- logist, if history had not preserved the memorials of a tre- mendous flood which happened in this district in the year 1755. It appears that two streams of lava flowed in that year, on the second of March, from the highest crater : they were immediately precipitated upon an enormous mass of snow, which then covered the whole mountain, and was ex- tremely deep near the summit. The sudden melting of this frozen mass, by a fiery torrent three miles in length, pro- duced a frightful inundation, which devastated the sides of the mountain for eight miles in length, and afterwards covered the lower flanks of Etna, where they were less steep, together with the plains near the sea, with great deposits of sand, scoriae, and blocks of lava. Many absurd stories circulated in Sicily respecting this event, such as that the water was boiling, and that it was vomited from the highest crater ; that it was as salt as the sea, and full of marine shells; but these were mere inven- tions, to which Recupero, although he relates them as tales of the mountaineers, seems to have attached rather too much im- portance. Floods of considerable violence have been sometimes produced on Etna, by the fall of heavy rains, aided, probably, by the melting of snow. By this cause alone, in 1761, sixty * Scrope, on Volcano s, p. 102. 424 GLACIER COVERED BY LAVA. [Ch. XXI. of the inhabitants of Acicatena were killed, and many of their houses swept away *. Glacier covered by a lava stream. A remarkable discovery has lately been made on Etna of a great mass of ice, preserved for many years, perhaps for centuries, from melting, by the singular accident of a current of red hot lava having flowed over it. The following are the facts in attestation of a pheno- menon which must at first sight appear of so paradoxical a character. The extraordinary heat experienced in the South of Europe, during the summer and autumn of 1828, caused the supplies of snow and ice which had been preserved in the spring of that year, for the use of Catania and the adjoining parts of Sicily and the island of Malta, to fail entirely. Great distress was felt for the want of a commodity regarded in these countries as one of the necessaries of life rather than an article of luxury, and on the abundance of which in some large cities the salubrity of the water and the general health of the com- munity is said in some degree to depend. The magistrates of Catania applied to Signer M. Gemmellaro, in the hope that his local knowledge of Etna might enable him to point out some crevice or natural grotto on the mountain, where drift snow was still preserved. Nor were they disappointed ; for he had long suspected that a small mass of perennial ice at the foot of the highest cone was part of a large and continuous glacier covered by a lava current. Having procured a large body of workmen, he quarried into this ice, and proved the superposition of the lava for several hundred yards, so as completely to satisfy himself that nothing but the subsequent flowing of the lava over the ice could account for the position of the glacier. Unfortunately for the geologist, the ice was so extremely hard, and the excavation so expensive, that there is no probability of the operations being renewed. On the first of December 1828, I visited this spot, which is on the south-east side of the cone, and not far above the Casa Inglese, but the fresh snow had already nearly filled up the * Ferrara, Descriz. dell' Etna, p. 116. Ch. XXI.] VOLCANIC ERUPTIONS IN ICELAND. 425 new opening, so that it had only the appearance of the mouth of a grotto. I do not, however, question the accuracy of the conclusion of Signor Gemmellaro, who being well acquainted with all the appearances of drift snow in the fissures and cavi- 13 Aristotelian system, 17 theory of spontaneous generation, 30 Arso, Campo del, volcanic eruption from the point called, 383 Arve, sediment transported by the, 266 section of the debris deposited by the, see diagram No. 6, 291 Asama-yama, in eruption in 1783, 474 Ashes, volcanic, immense quantity ejected from the Tomboro mountain,! 8 1 5, 463 distance to which they were trans- ported, 463 Asia always subject to earthquakes, 12 coast of changed, 25 causes of the extreme cold of part of, 123 Minor, gain of land on the coast of, 352 Astruc on the advance of the delta of the Rhone, 266 Atchafalaya, drift wood in the river, 215 section of the banks of the, 281 Atlantic, La Place on the mean depth of the, 133 its relative level, 334 rise of the tide in, 335 Atlantis, submersion of, 12 Atrio del Cavallo, 395 Australia, coral reefs of, 150 Auvergne, Desmarest on the relative ages of the volcauos of, 67 - Montlosier on volcanos of, 68 salt deposited by springs in, 247 carbonic acid gas plentifully disen- gaged in, 247 Ava, Mr. Crawfurd's discovery of fossils in, 38 fossil wood of, M. de la Hire's me- moir on, 1692 (note), 38 Avalanches, cattle and men buried by in Switzerland, 111 Avernus, lake, mephitic vapours formerly exhaled from, 379 a crater of an extinct volcano, 329 Avicenna on mineralogy, 24 Azof sea, said to have been united with the Caspian, 367 new island thrown up in, 368 Azores, icebergs drifted from Baffin's Bay to the, 128 Azores, new islands thrown up near, 447, 504 siliceous springs of the, 243 BABBAGE, Mr., his examination of the coast near Puzzuoli, 518 on the mole called Caligula's bridge, 520 Baden, gypseous springs of, 243 Baffin's Bay, enormous icebergs in, 125 Bagnes, valley of, bursting of a lake in the, 222 Baise, changes on the coast of the bay of, 517 ground plan of the coast of the bay of, see woodcut No. 30, 518 sections of the strata in the bay of, see woodcuts Nos. 31 and 32, 519 numerous proofs of subsidence in the bay of, 524 re-elevation of the coast of the bay of, 527 Bakewell, Mr., Jun., on the Falls of Nia- gara, 208 Baku, escape of inflammable gas in the district of, 1 6 . volcanic tract called the field of fire near, 366 Balaruc, thermal waters of, in the delta of the Rhone, 267 Baldassari on the grouping of organic remains in theSienese territory, 54 Baltic sea, Celsius* theory of the diminu- tion of, 46 deltas of the, 260 supposed lowering of the level of the, 260 its level may have been lowered by the widening of its channel, 263 action of currents on its shores, 336 Banchina in Sicily, sea deepened by earthquake near, 480 Banks on the Basalt of Hecla, 67 Barren island, a supposed crater of ele- vation, 445 height of the cone of, &c. 446 view of the cone and crater of, see woodcut No. 17, 446 supposed section of, 450 Basalt of Hesse, Raspe on the true na- ture of, 1768, 66 Werner's erroneous theory of, 66 of Hecla, Banks, Solander, and Troil, on, 1772, 67 of the Vivarais, Guettard on, 67 of Velay and Vivarais, Faujas on, 1779, 67 columnar, of Central France, 396 Barsoe, rate of loss of land in the island of, 336 Bassano, Mr. Murchison on the tertiary deposits of, 158 INDEX. 557 Batavia, earthquake at, 1699, 511 . . the river obstructed and floods caused, 511 cattle, &c., drowned, 511 Bauza, his chart of the Gulf of Mexico, 354 Bayfield, Capt., on the geology of Lake Superior, 258 Bay of Bengal, its depth opposite the mouth of the Ganges, 277 Bayonne, new channel cut by the river Adour at, 343 Beachey Head, fall of the chalk cliffs of, 319 Beaufort, Capt., on the gain of land on the coast of Asia Minor, 353 on the great rise of the tides at Chepstow, 294 Beaumont, M. Elie de, on the relative age of mountain chains, 158 Beechey, Capt., on the elevation of the Bay of Conception, 507 Belcher, Capt., on the elevation of Con- ception Bay, 507 Bell rock, stones of two tons weight thrown up by storms on the, 303 Bergmann, on waste of Yorkshire coast, 306 Beshtau, earthquakes in the province of, 503 Bewick, 313 Bhooi, town of, destroyed by earthquake, 465 Bies Bosch, new bay formed by the sea in Holland, 328 Bigsby, Dr., on the height to which autumnal gales raise the waters of Lake Superior, 258 Bima, anchorage at, altered by earth- quake, 1815, 464 Bison, found fossil in Yorkshire, 114 Bistineau, a new lake formed by the Red River, 218 Bitumen, oozing from the bottom of the sea near Trinidad, 250 Bituminous springs, 249 shales, 250 Bizona, town submerged, 21 Black lake, 218 Black sea, calcareous springs near the, 241 Blue mountains in Jamaica shattered by earthquakes, 515 Bluffs of Mississippi described, 213 Boase, Mr., his account of the Lionnesse tradition, 324 on inroads of sea near Penzance, 323 on drift sand in Cornwall, 344 Bogota, earthquake of, 1827, 459 Bologna, institute of, supports diluvia hypothesis, 47 3onaiutus, on the subsidence of the coast of Sicily, 512 Bore, tidal wave called the, 333 its cause and velocity, 333 the, very frequent in the Bristol channel, 333 very common in the Ganges, 334 Boscomb chine, 321 Boscovich, his theory of earthquakes, 1772, 61 supposed earthquakes to have grown feebler, 61 Bothnia, gradual conversion of the gulf of, into dry land, 261 Boucau, new channel formed by the Adour at, 343 Boue, M., on the strata of the Pyrenees, 158 Bourbon, island, volcanic, 372 Bourdones river, shoal upheaved at its mouth, 473 Boyle, remarks of on the bottom of the sea, (note) 35 Bracini, his description of Vesuvius before the eruption of 1631, 388 Brahmins, 8 Brander, on the fossils of Hampshire, 59 Brenta, delta of the, 270 Brieslak, on the subsidence of the mole at Puzzuoli, 525 on the temple of Serapis, 526 on prismatic lavas of Vesuvius, 397 Brighton, waste of the cliffs of, 31 9 Brine springs, 246 Bristol channel, velocity of currents in the, 295 Brocchi, his discourse on fossil concho- logy, (note) 26 on Burnet's theory, 46 on the deposition of the Subapen- nine beds, 155 his account of the various writers on the delta of the Po, 270 Broderip, Mr., on the opossum of Stones- field, (note) 173 shells from Conception Bay exa- mined by, (note) 503 Brongniart, M. Ad., on the fossil plants of the coal formation, 116 on the fossil plants of strata between the coal and the chalk, 1 16 on the proportion of ferns to other plants in islands, 142 Brongniart, M. Alex., on the comparative insignificance of modern lava- streams, 430 on shells of existing species at great heights in Sweden, 264 Browallms, on the filling up of the gulf of Bothnia, 262 558 INDEX. Buckland, Dr., on fossil elephants, &c., in India, (note) 9 on mammiferous remains of the Isle of Wight, 175 on the rocks of the Bristol coal- field, 152 on dicotyledonous wood of North- umberland coal-field, 169 on caves in limestone rocks, 242 BufFon, his theory of the earth, 1749, 54 his system opposed to that of Hooke, Ray, and Moro, 54 his theory reproved by the Sor- bonne, 54 his ' Declaration' renoxmcing his theory of the earth, 55 on the secondary origin of moun- tains, 55 Bare, town submerged, 21 Burnes, Lieut. A., on the earthquake of Cutch, 1819, 466 Burnet, his theory of the earth, 42 on the causes of the deluge, 43 general conflagration described by,43 on the seat of Paradise, 43 praised by Steele, Addison, and Warton, 44 Voltaire's remarks on the theory of, 75 BurrampoottT, delta of the, 275 Butler, Burnet's theory concerning Para- dise, ridiculed by, 43 Byron, Lord, cited, on the permanency of the ocean, 530 CADO lake, 218 Caesar on the Druids, 22 Caithness schists, scales of a tortoise, &c., found in the, 171 Calabria, Scilla on the fossils of, 33 recent fossils of, 107 earthquake of 1783 in, 475 geological description of, 477 ' reflections on the earthquake of 1783 in, 496 Calcaire Grossier, organic remains of the, 115 Calcareous matter, immense quantity conveyed to the sea, 242 Calcareous springs of central France, 230 of the valley of the Elsa, 230 of Tuscany, 23 1 between the Caspian and Black seas, 241 Calcutta, beds cut through in sinking a well at, 278 Caldeira, siliceous sinter of the, 243 Caldera, central cavity in the isle of Palma, see woodcut No. 16, 444 geological description of the, 445 supposed by Von Buch to be a cra- ter of elevation, 445 California, five volcanos in, 363 Callao, town destroyed by the sea, 368 part of the coast near, converted into a bay by earthquakes, 5 10 great rise of the sea at, 510 reports of subsidences in, 510 Caltabianca. river, lava excavated by the, 204 Camden, his account of traditions of losses of land in Pembrokeshire, &c., 324 Campagna di Roma, calcareous deposits of the, 236 Canary islands, volcanic eruptions in the, 372, 435 Canopus, an island in the time of Scylax, 273 overwhelmed by the sea, 274 Cantal, Plomb du, described, 451 Cape May, rate of encroachment of the sea at, 333 of Good Hope, icebergs sometimes seen off, 128 Caraccas, earthquakes in the, 1790, 473 destroyed by earthquake, 1812, 468 Carang Assam volcano in eruption about 1808, 465 Carbonate of lime abundant in the delta of the Rhone, 269 Carbonated springs, 247 Carbonic acid gas plentifully disengaged in Auvergne, 247 its effects on rocks, 249 Cardiganshire, ancient tradition of the loss of land in, 324 Carelli, Signor, on the temple of Serapis, 522 Carew -on St. Michael's mount, 324 Cariaco, bed of the sea raised near, 504 Caribbean sea, tides scarcely perceptible in, 335 Caridi, river, its course changed by earth- quakes, 490 Carpenter, Dr., on the encroachment of the sea at Lyme Regis, 323 Casalmaggiore, island carried away by the Po, opposite to, 211 Caspian, Pallas on the former extent of the, 62 calcareous springs near the, 241 evaporation of the, 269 subterranean movements violent along its borders, 366 said to encroach on the land, 366 inflammable gas, &c., on its western shores, 366 its level lower than that of the Black Sea, 367 said to have been united with the sea of Azof, 367 Cassander, on the duration of the Annus Magnus, 11 INDEX. 559 Cassas, M., his account of the earth- quake in Murcia, 459 Catania, overwhelmed by lava in 1669, 419 destroyed by earthquakes, 512 Catastrophes, general, two kinds of, taught by the Stoics, 1 1 Catcott, on the deluge, 1761, 57 laboured to refute the diluvian theory of Bishop Clayton, 57 . insisted on the universality of the deluge, 58 refers to traditions of deluges in different countries, 58 Cattegat, devastations caused by the current in the, 336 Catwyck, loss of land at, 329 Caucasus, Pallas on the calcareous springs of the, 241 - earthquakes frequent in the, 368 < abounds in hot springs, 368 subsidence caused by earthquakes in the, 503 Cavanilles on the earthquake of Quito in 1797, 473 Caverns in limestone caused by water charged with carbonic acid, 242 on Etna, 420 Caves, abundance of animal remains in, 177 Celestial mountains, tigers found to the north of the, 113 Celsius, on the diminution of the Baltic, 46, 260 - controversy caused by the theory of, 46 Censorinus, 17 Central France, lavas excavated in, 203 . comparison between its lavas and those of Iceland, 428 Central heat, remarks on the supposed diminution of, 162 Cephalonia, earthquakes in the island of, in 1783, 478 Cesalpiuo, on organic remains, 1596, 30 Chalk, Mr. Mantell on the fossils of the, 161 . of Goslar, error of Werner in his account of the, 66 remarks on its deposition, 159 Changes now in progress not easily ob- served by man, 92 Chasm near Oppido formed by earth- quake of Calabria, 1783, 484 . in the hill of St. Angelo, formed by the same earthquake, see wood- cut No. 24, 486 Chaluzet, calcareous spring rising through gneiss at, 230 volcanic cone of, 248 Chepstow. great rise of the tides at, 294 Cheshire, brine springs of, 246 hesil Bank, its size and composition, 322 Chesilton, overwhelmed by storm of November, 1824, 323 Chili, elevation caused by one earth- quake in, 90 numerous volcanos in, 361 earthquake of 1822 in, 460 earthquake of 1760 in, 504 Chimborazo, height of, insignificant when compared to the earth's diameter, 131 China, excessive climate of, 124 - violent earthquakes have been felt in, 366 Chines, or narrow ravines described, 321 Christ Church Head promontory, wastes slowly, 321 Chronological computations of the age of deltas, 255 Cicero, cited, 33 Cimbrian deluge, 337 Cinquefrondi, changes of the surface caused by landslips in, see wood- cut No. 27, 491 Circular hollows formed by earthquakes in Murcia, 459 formed by earthquakes in Chili, 1822,461 formed by earthquake in Calabria, 1783, see wood-cut No. 28, 493 .- section of one of these, tee wood- cut No. 29, 494 Civita Vecchia, granular rock deposited by springs at, 236 Clashbinnie, organic remains in the old red sandstone of, 170 Clayton, Bishop, on the deluge, 57 Clennont, calcareous springs at, rising through volcanic peperino, 230 Climate of Europe, Raspe on the former, 59 change of, in the northern hemi- sphere, 105 direct proofs of a change in, 106 proofs of a change of, from size of fossil and recent shells in Sicily, &c., 107 proofs from analogy of a chancre of, 109 remarks on the extent of change in, 118 . on the causes of vicissitudes in. 120 its connexion with the distribution of land and sea, 121 change of, in the plain of Malpais, caused by volcanic eruptions, 143 Climates, definition of insular and ex- cessive, 111 places having insular or excessive, 560 INDEX. Coal formation, not found in the south of Europe, 145 Coal strata, M. Ad. Brongniart on the fossil plants of the, 116 insular character of the plants of the, 148 . rarity of dicotyledonous wood in the, 169 Colebrooke, Mr. H. T., on the crocodiles of the Ganges, 279 Colebrooke, Major, on the course of the Ganges, 283 on the transportation of matter by the Ganges, 283 Colle, travertin of, 23 1 College, transportation of rocks by the, 201 Collini, on the igneous rocks of the Rhine, 1774, G7 Colombia, earthquakes in, 504 Colonna, his theory of organic remains, 3 1 first distinguished between marine and land fossil shells, 31 Comet, deluge attributed by WhUton to a, 44 Concentric travertin of Tivoli, 238 Conception, destruction of the town of by earthquake, in 1750, 507 great elevation of the bay of, 507 Conflagration of the world, 28 of the earth, described by Burnet, 43 Conglomerate forming at the foot of the maritime Alps, 289 forming at the mouth of the Isonzo, 271 volcanic, on the coasts of Sicily and Ischia, 43!) Convergence of deltas, 288 Conybeare, Rev. \V. D , his account of Lister, 36 on the rocks of the Bristol coal field, 152 on the waste of Reculver cliffs, 315 Cook, Captain, his conjecture as to the existence of high land near the South Pole, 126 Copernican theory, edicts against re- pealed at Rome in 1818, 78 Cordier, M., on the temperature of the interior of the earth, lf>4 Cordilleras shaken by earthquakes in 18 12 and 1827,460,409 Cork, dicotyledonous wood in the gray- wacke of, 1 69 Cornwall, Mr. Boase on waste of the cliffs of, 323 tradition of loss of land in, 324 land inundated by drift sand in, 344 Cortesi, 61 Cosmogony distinct from geology, 5 of the Hindoos, 6 Egyptian, 10 of the Koran, 25 Costantini, deluge vindicated by, 47 Cotopaxi, 362 Covelli, M., on the elevation of the tem- perature of a hot-spring in Ischia by an earthquake, 459 Cowper, 77 Cramer, Mr., on earthquake of New Madrid, 470 Craters of elevation, Von Buch's theory of, considered, 442 Crawfurd, Mr., his discovery of fossils in Ava, 38 Creation, Mahomet's account of the, 25 , Moro's theory of the, adapted to the Mosaic account, 48 Cremona, lakes filled up or drained near, 210 Crimea, waste of the cliffs in the, 336 Crocodiles of two species in the delta of the Ganges, 279 Cromer, waste of the cliffs of, 308 its ancient site now part of the German Ocean, 308 Cruickshanks, Mr., on the earthquake of Chili in 1822,460 Culver cliff', composed of chalk, 320 Cumana, earthquake of, 1797, 410 town of, destroyed, 410 Current along the shores of Egypt, 274 along the coast of Africa, 353 sediment of the Amazon transporte d by, 354 Currents from equatorial regions, 124 from the Pole to the Equator, 136 section of debris deposited by op- posing, see diagram No. 6, 291 causes of, 295 velocity of, 295 destroying and transporting power of, 21)3 in estuaries, their power, 303 in the Straits of Gibraltar, 338 sediment conveyed to immense dis- tances by, 352, 354 gain of land on the coast of Syria, caused by, 352 reproductive effects of, 346 their course on the British shores, 346 Curves of the Mississippi, 213 Cutch, in the delta of the Indus, earth- quake of, 1819,465 great changes of level caused by the earthquake of, 465 Cuvier, his eloge of Desmarest, 69 on the opossum of Stonesfield, 173 his remark on the durability of the bones of men ; 177 INDEX. 661 Cyprus, rocks reported to have risen near, during earthquake in 1822, 462 DANIELS, Mr., on the trade-winds, 1 36 Danish Archipelago, undermined by cur- rents, 336 Dante, embankment of rivers noticed by, 212 Dantzic, waste of land near, 336 Darby, on the drift wood of the Missis- sippi, 216 his account of the new lakes formed by the Red River, 218 on the marine strata of Lower Louisiana, 219 on the Delta of the Mississippi, 281 Daubeny, Dr., on the volcanic origin of the country round the Dead Sea, 246 on the vicinity of volcanos to the sea, 540 D'Aubuisson, his eulogium of Smith's map of England, 81 Davy, Sir H.,on the waters of the lake of the Solfatara, 237 on the formation of travertin, 237 his theory of progressive develop- ment, 166 . on the rebuilding of cities on the same spot after their destruction by lava, 410 Davy, Rev. C., on the Lisbon earthquake of 1755, 505 Dead Sea, muriatic salts abundant in its waters, 246 the country around it volcanic, 370 Dee, river, bridge over, swept away by floods, 200 Deficiency of ancient accounts of earth- quakes, 457 De la Beche, Mr., on the delta of the Rhone in the lake of Geneva, 253 on the earthquake of Jamaica, 1692, 514 De la Hire, on fossil wood from Ava, 1692, 38 Delhi territory, elephants covered with shaggy hair in the, 112 Delta of the Rhone, in Lake of Geneva, 253 proofs of its advance in the last eight centuries, 253 of the Rhone in the Mediterranean, 265 its gradual advance, 266 in great part composed of calca- reous rock. 268 of the Po, 269 of the Isonzo, 270 of the Tagliamento, 270 of the Brenta, 270 VOL. I. Delta of the Adige, 270 of the Nile, 272 changes in, since the time of Ho- mer, 273 of the Burrampooter, 275 of the Ganges, 275 animals inhabiting the, 276 stratification of the, 290 of the Mississippi, 280 its advance since New Orleans was built, 281 its stratification, 290 Deltas, chronological computations of the age of, 255 of Lake Superior, 258 of the Baltic, 260 oceanic, 275 remarks on the grouping of strata in, 286 convergence of, 288 independent in same basin, 287 of the Po and Adige have become confluent, 288 of the Ganges and Burrampooter have probably become confluent in historical times, 288 De Luc, his treatise on geology, 1809, 77 affirmed that religion was attacked by geology, 77 on the excavation of valleys, 79 his remarks on the age of deltas, 257 De Luc, M. G. A., his natural chronome- ters, 345 Deluge, of Deucalion, 17 described in the Koran, 26 mentioned by Persian magi, 26 fossil shells referred to the, 27 Ray on the causes of the, 41 Burnet and Woodward's account of the, 42 - attributed by Whiston to a comet, 44 all stratified deposits referred to, by Whistou, 44 cause of, how explained by Leib- nitz, 45 Scheuchzer's theory of the, 46 Pluche on the, 46 truth of the, supported by Costan- tini, 47 Catcott's treatise on the, 57 Bishop Clayton's explanation of the, 57 Cimbrian, 237 Deluges part of the present course of Nature, 101 . local, how caused, 220 traditions of different, 367 Denmark free from earthquakes, 265 Deposition of sediment, rate at which the finer kinds subside, 355 Derby shire,"Whitehurst ou the rocks of, 61 2 O 5G2 INDEX. Deshayes, M., on the fossil shells of the Paris basin, 115 on the Valley of the Meuse, 197 Desmarest considered geology a branch of physical geography, 5 Arduino's views confirmed by, 67 on Auvergne, 67 character of his map of, 67 his answer to a Neptunist, 69 on the separation of England from France, 317 Destruction and renovation of the world, an oriental doctrine, 1 Deterioration of mankind, 1 1 . origin of the doctrine, 1 1 Deucalion's deluge, Aristotle's opinion of, Dicotyledonous wood in the coal strata of Northumberland, 169 in the graywacke of Cork, 169 Dikes in Vesuvius, how formed, 393 Diluvial theory, 33 progress of geology retarded by the, 34 opposed by geologists of Tuscany, 47 - supported by Institute of Bologna, 47 Dimlington height, rapid waste of, 305 Diodorus Siculus on early eruptions of Etna, 416 Dion Cassius, his account of the eruption of Vesuvius, A.D. 79, 382 Dioscorides, 29 Disputations, scholastic, effect of in dark ages, 28 Doggerbank, Capt. Hewett on the, 350 Dollart, formation of the estuary of the, 331 Dolomieu on the strata of the Val di Noto, Vicentin, and Tyrol, 68 on the ancient lavas of Etna, 68 on the decomposition of granite,248 on the earthquake of 1783 in Cala- bria, 477 Don, transportation of rocks by the river, 201 Donati, his investigation of the bed of the Adriatic, 1750, 53,96,270 Dorsetshire, description of a landslip in, 322 Dover, waste of the chalk cliffs of, 316 depth of the sea near, 316 formation of the Straits of, 317 Dranse, river draining the Valley of Bagnes, 222 shifted its course after the debacle of 1818 in Valley of Bagnes, 224 Drift sand of the African deserts, cities buried under, 344 Drift wood of the Mississippi, 214, 281 Drongs, granitic rocks of Shetland wo away by the sea, see wood-cuts Nos. 9 and 10, 301 Druids, their belief in future catastrophes of the world, 22 Dufrenoy, M.. on the relative age of the Pyrenees, 158 Dunes, hills of blown sand, coast of Nor- folk protected by, 307 on coast of France, 343 near the estuary of the Tay, 343 on the shores of the Nile, 344 Dunwich, its gradual destruction by the sea, 312 Gardner's account of the destruc- tion of, 312 Durham, magnesian limestone of, in- vaded by the sea, 304 EARTH, antiquity of the, 27 centre of gravity of the, a change in it supposed by Ray, 41 axis of the, has not changed, ac- cording to Newton and Laplace, 44 a change in the axis of the, a lead- ing dogma in Burnet's theory, 44 inorganic causes of change on its surface, 192 Earthquake in Murcia, 1829, 459 in Ischia, 1828, 459 in Bogota, 1827, 459 in Chili, 1822, 460 in Aleppo, 1822, 462 in the Ionian isles, 1820, 462 in the island of Sumbawa, 1815, 463 of Cutch, 1819, 465 in Caraccas, 1812, 468 in South Carolina, 1811, 469 in the Aleutian isles, 1806, 470 in Quito, 1797, 472 in Cumana, 1797, 473 in Caraccas, 1790, 473 in Sicily, 1790, 473 in Java, 1786, 473 in Calabria, 1783, 475 duration of the shocks, 475 numerous accounts of, 476 extent of the territory convulsed,477 inGuatimala, 1777, 502 in Java, 1772, 503 in the Caucasus, 1772, 503 in Java, 1771, 503 in St. Domingo, 1770, 503 in Colombia, 1766, 504 in Chili, 1760, 504 in the Azores, 1757, 504 in Lisbon, 1755, 504 in St. Domingo, 1751, 507 in Conception, 1 750. 507 in Peru, 1746, 509' in Karntschatka, 1737, 510 INDEX. 503 Earthquake in Martinique, 1727, 511 in Iceland, 1725, 511 inTeneriffe, 1706, 511 in Java, 1699, 511 in Quito, 1698, 512 in Sicily, 1693, 512 in the Moluccas, 1693, 513 in Jamaica, 1692, 513 Earthquakes, Asia always subject to, 12 Egypt nearly exempt from, 12 Strabo's theory of. 20, 39 Hooke on the changes caused by, 38 under the sea, Hooke's opinion of, 39 simultaneous extent of, mentioned by Hooke, 39 Lazzaro Moro on, 1740, 47 Generelli's account of, 51 Michell on the cause and pheno- mena of, 57 originality of Michell's theory of, 57 Raspe's theory of, 1763, 58 Boscovich on the effects of, 1 772, 6 1 Hutton's theory of, no advance on that of Hooke, 72 Hutton's theory of, compared to Generelli's, 73 energy of, probably uniform as re- gards the whole earth, 73 force of, confined for ages to one place, 73 their gradual operation in former ages, 100 earth's surface continually remo- delled by, 130 in the basin of the Mississippi in 1812, 219 all countries liable to slight shocks of, 373 their effects, 457 deficiency of ancient accounts of, 457 atmospheric phenomena attending, 458 difficulty of measuring the effects of, 479 excavation of valleys aided by, 498 reflections on those of the nine- teenth century, 471 reflections on those of the last one hundred and forty years, 515, 545 deficiency of historical records con- cerning, 516 renovating effects of, 547, 553 uniformity of the action of, 531 opinions of the ancients concerning, 533 and volcanos, their relation, 534 cause of the wave-like motion of, and retreat of the sea during, 542 Ecchellensis, Abraham, 19 Edmonston island at the mouth of the Ganges, 277 Egypt, hills of, known by the priests to contain fossil shells, 8 nearly exempt from earthquakes, 12, 371 Egyptian cosmogony, 10 theory of eternal succession of events, 180 Ehrenberg, M., his discovery of the Ben- gal tiger in Siberia, 113 Elephant, fossil in India, (note) 9 fossil, in ice on shores of the North Sea, 62 fossil tusks of the, found at Puglia, 29 fossil of Italy, Targioni on the, 56 Elephants covered with shaggy hair in the Delhi territory, 112 Elevation, of land by earthquakes, Hooke on the, 38 of continents, not by paroxysmal eruptions, 100 of the coast of Chili, 460 and subsidence in the delta of the Indus, 465 of the Bay of Conception, 507 and subsidence, proportion of, 548 craters, Von Buch's theory of, con- sidered, 442 origin of the deep gorge in, 452 Elk, fossil, noticed by Generelli, 50 Elsa, travertin formed by the, 230 Embankment, system of in Italy, 211 noticed by Dante in the fourteenth century, 212 gain of land in the Adriatic more rapid in consequence of, 270 Engelhard, on the Caspian sea, 367 England, Smith's map of, 80 D'Aubuisson's eulogium on Smith's map of, 18 . waste of land on the east coast of, 304 encroachments of the sea on the south coast of, 318 slight shocks of earthquakes felt in, 265, 373 Epomeo, Monte, structure, height, &c.,378 of submarine origin, 378 volcanic cones on, 378 Equinoxes, precession of the, 127 Eratosthenes, 20 Eruptions, volcanic, number of per year, 454 Erzgehirge, mistake of Werner as to the mica slate of the, 65 Escher, M., on the flood in the valley of Bagnes, 223 Essex, inroads of the sea on the coast of, 314 202 564 INDEX. Estuary of the Thames both gains and loses land, 315 Estuaries described, 304 new ones formed by the sea in Hol- land, 331 kept open by the combined influ- ence of tides and currents, 347 tide longer flowing down than up in, 347 gain of land in, does not compen- sate loss of coast, 348 Etampes, Voltaire's remarks on the dis- covery of fossil bones near, 76 Etna, Dolomieu on ancient lavas of, 68 difference between the lavas of, and those of submarine volcanos, 148 lavas of, excavated by rivers, 204 quantity of lava poured out in 1669, by, 284 comparison between the lavas of, and the sediment of the Ganges, 284 - unusually active during the great pause in the eruptions of Vesu- vius, 384 its height, circumference, &c., 414 divided by nature into three re- gions, 414 frequent destructions of its cone, 416 minor volcanos on, 416 buried cones on the flanks of, 416 has been in activity from the earli- est times, 417 . great eruption of 1669, 417 formation of Monti Rossi on, 417 fissures on the sides of, 418 towns and villages on, overflowed by the lava of 1669, 419 subterranean caverns on, 420 eruptions of 1811 and 1819, 421 cones thrown up in 1819,422 . great floods caused by the melting of snow on, 423 glacier found under lava on, 424 manner of preserving snow on the higher regions of, 425 , its cone truncated in 1444, 448 said to be an ancient crater of ele- vation, 451 its appearance during Calabrian earthquake, 495 Euganean Hills, ancient lavas of, 373 Engulphing of houses, &c., during Cala- brian earthquake, 484 Euphrates, Pliny on the gain of land at its mouth, 332 Euxine burst its barrier, according to Strabo, 20 gradually tilling up, 20 cliffs undermined by currents in the, 336 Evaporation, quantity of water carried off by, 269 Excavation of valleys, 496 Hutton and De Luc's theory of the, 79 Excessive climates, description of, 124 Extinct species, Hooke's remarks on, 37 Eyderstede, overwhelmed by the sea, 337 Eyfel, 220 FABIO Colonna, 31 Fair Island, action of the sea on the sandstone of, 302 Falconi on the elevation of the coast of the Bay of Baise, 528 Falloppio, his doctrine concerning orga- nized fossils, 29 Falls of Niagara, 206 of St. Mary, only outlet to Lake Superior, 259 Faraday, Mr., on the slow deposition of sulphate of baryta powder, 355 Farquharson, Rev. J., on the great floods in Scotland, in 1829, 201 Faujas, on the Velay and Vivarais, 1779, 67 Fault in the tower of Terranuova caused by an earthquake, see wood-cut No. 20, 481 Ferishta, 9 Ferns, &c., silicified by springs in St. Michael's, 244 Ferrara, his account of the lava poured out from Etna in 1669, 285 his account of floods on Etna, 4 : 24 on earthquake of 1790 in Sicily, 473 Ferruginous springs, 245 Fetlar, effect of lightning on the rocks of, 298 Fez, frequently suffers from earthquakes, 371 Fife, coast of, submarine forests on the, 303 encroachments of the sea on the coast of, 304 Findhorn, old town of, swept away by the sea, 302 Fissures, sulphur, &c., ejected by, in Sicily, 473 sulphureous vapours emitted by, in Java, 474 different elevation of the sides of, in Calabria, caused by earthquake of 1783, 480 near Polistena, caused by earth- quake, see wood-cut No. 19, 480 near Jerocarne, see wood-cut 22, 483 , cause of the opening and closing of, 483 dimensions of new ones in Cala- bria, 485 INDEX. 565 Fitton, Dr. on the Maestricht beds, 161 Flainborough Head washed into caves by the ocean, 305 Fleming, Dr., on uniformity in climate, 106 his remark on the food of the fos- sil elephant, 110 on submarine forests in the estua- ries of the Tay and Forth, 303. 310 Flint, on the length of the course of the Mississippi, 212 on the population of the Mississippi valley, 217 on the earthquakes in the Missis- sippi valley, 470 Floods, bursting of lakes, &c., 220 in North America, 221 in the valley of Bagnes. 224 in Scotland, August, 1829, 200 at Tivioli, 225 Oil Etna, caused by melting of snow, 423 Florence of Worcester, his account of a storm in Nov. 1099, 323 Florus, his account of the Cimbrian De- luge, 337 Fluviatile formations mentioned by Steno, 32 Foah, advance of the delta of the Nile near the city of, 272 Folkestone, subsidence of land at, 318 Foutenelle, his eulogy on Palissy, 31 Forbes, Mr., on the subsidences in the Bay of Baiae, 525 on the temple of Serapis, 526 Forfarshire, encroachments of the sea on the coast of, 303 Forio. masses of tuff thrown down by an earthquake near, 459 Formosa, violent earthquakes in, 365 Forsyth, his description of the climate of Italy, 412 Fortis, on the Arabian doctrine of new genera and species, 20 and Testa, their controversy on fos- sil fish of Monte Bolca, 60 views of Arduino confirmed by, 67 Fossil shells, attributed to a ' plastic vir- tue ' by Dr. Plot, 35 Lister's opinion of, 36 speculations concerning their na- ture, 33 formerly all referred to the Deluge, 33 Fossil plants of the coal strata, 116, 118, 148, 169 Fossils, Brander's argument against, re- ferring to the deluge, 59 Fourier, Baron, on. the temperature of the spaces surrounding our atmos- phere, 138 oil central heat, 162 Fracastoro, his opinion concerning orga- nic remains, 27 France, art of mining how taught in, 63 its coast the constant prey of the waves, 325 villages of, washed away by the sea, 325 French, their great progress in the study of organic remains, 82 Fresh-water formations of the Paris basin, 115 Fresh-water and marine strata, alterna- tions of, described by Geiierelli, 50 Freyberg, school of, 71 Funchal, rise of the sea during earth- quake at, 506 GABEL Tor, a volcano in Arabian gulf, 372 Ganges, delta of the, 275 its ancient mouths, 276 size and rate of advance of its delta, 276 inundations of the, 280 Reunell on the quantity of earthy matter in the waters of the, 283 Renuell on the quantity of water discharged by the, 283 and Burrampooier not vet com- pletely united, 289 stratification of the deposits in its delta, 290 Garachico, in TenerifFe, overwhelmed by lava, 5 1 1 Gardner, his account of the destruction of Dunwich by the sea, 312 Gas, inflammable, escape of, 16 Gases exhaled by volcano s, 540 Gaulish Druids, 22 Gemmellaro, his account of the eruption of Etna in 1811, 421 his discovery of ice under lava, 424 Generation, spontaneous, theory of, 30 Genereili, his exposition of the state of geology in Europe in the middle of 18tli century, 49 on organic remains, 50 on vegetable productions found in different states of maturity, 50 on fossil elephants, elks, &c., 50 on alternations of marine and fresh- water strata, 50 on grouping of marine aaimals in strata, 50 teaches that fossils cannot be ac- counted for by the deluge, 50 his explanation of the imbedding of marine animals in mountains, 51 on the effects of earthquakes iu recent times, 51 waste of land by running water described by, 5 1 " 566 INDEX, Generelli, his opinion that mountains could not be so great if their ruins were not repaired, 52 his theory of primary rocks, 71 his theory of earthquakes compared to Button's, 73 Geneva, lake of, men drowned above Martigny floated into the, 224 gradually filling up, 253 Mr. De la Beche on the delta of the Rhone in the, 253 Geognosy of Werner, 63 Geography, proofs of former changes in physical, 144 Geological evidence, its value depends on the assumption of uniformity of nature, 190 Geological Society of London, formation of, 81 good effects resulting from the foundation of the, 82 Geological theories, causes of error in, 86 Geology defined, 1 compared to history, 1 its relation to other physical scien- ces, 2 distinct from cosmogony, 5 considered by Werner as part of mineralogy, 5 causes of its retardation, 33, 76, 85 state of, in Europe, before middle of last century, 49 applied to the art of mining by Werner, 63 remarks of Kirwan and De Luc, on the connection of, with religion, modern progress of, 82 practical advantages derived from the study of, 84 Georgia, in the island of, perpetual snow to the level of the sea, 127 Gerbanites, an Arabian sect, on extinc- tion of species, 19 German Ocean gradually filling up, 350 Germany, art of mining, how taught in, 63 Geysers of Iceland, 244, see wood-cut No. 32, 536 - cause of their intermittent action, 536 supposed section of the subterranean reservoir and pipe of one of the, see wood-cut No. 33, 538 Gian Greco, fall of the cliffs on the sea- coast near, during the earthquake of 1783, 494 Gibraltar, depth of the Mediterranean near, 272 Straits of, 338 - supposed under-current in the, 341 Girard, M., his analysis of the mud of the Nile, 273 Girard, M., on the former union of the Mediterranean and Red Sea, 352 Gironde, tides in its estuary, 347 Glacier discovered under lava on Etna, 424 Glaciers, formation of, 112 of Spitzbergen, 112, 125 transportation of rocks by, 202 Glen Tilt, granite veins of, discovered by Button, 71 Gloucestershire, gain of land in, 324 Golden age, doctrine whence derived, 1 1 Goodwin Sands, 316 Gorge, deep, said to occur in all elevation craters, 446 Gothland, Linnaeus on the increase of land near, 261 Graham, Mrs., on the earthquake of Chili in 1822,462 Grampians, Hutton's examination of the, Granite, disintegration of, in Auvergne, . of the Hartz, Werner on the, 65 248 veins, Hutton's discovery of, in Glen Tilt, 71 veins, importance of their discovery, Granitic rocks of Shetland, action of the sea on, see wood-cuts Nos. 9 and 10, 301 Grecian archipelago, Raspe on the new isles of the, 59 volcanos of the, 440 chart and section of, see wood-cut No. 15, 441 Greenland, why colder than Lapland, 123 sometimes shaken by earthquakes, 372 Grimaldi, on the earthquake of 1783 in Calabria, 476 on the dimensions of the new fis- sures and ravines in Calabria, 484 on the effects of the Calabrian earth- quake on springs, 487 Grind of the Navir, passage forced by the sea in the Shetland islands, see wood-cut No. 8, 300 Grosse, Dr., on the baths of San Filippo, 233 Grotto delle Cane, 247 Guarapica river, new rock thrown up in the, 504 Guatimala, active volcanos in, 362 town of, with eight thousand fami- lies, swallowed up by earthquakes. 1777, 502 Guettard, on the Vivarais, 67 Guiana, its maritime district formed by the sediment of the Amazon, 354 Gulf stream, 124, 296 INDEX. 567 Gulf stream, Scoresby's remarks on the, 125 Gunnell, Mr., on the loss of land in the Isle ot'Sheppey, 315 HALL, Sir James, his experiments on rocks, 70, 545 Hall, Captain, on the Falls of Niagara, 206 on the width of the Mississippi at its junction with the Missouri, 212 on the islands in the Mississippi, 214 on drift-wood in the Mississippi, 215,281 Hamilton, Sir W.,on the thickness of the mass covering Herculaneum, 403 on the earthquake of 1783 in Cala- bria, 477 on the number of persons who perished during the Calabrian earthquake, 495 on the earthquakes attending the eruption of Monte Nuovo, 527 on landslips nearMileto, 491 on the great landslip near Terra Nuova, 489 Hampshire, Biander on the fossils of, 59 Harcourt, Rev. W. V. V'., on bones of the mammoth, &c., in Yorkshire, 114 Harcourt, Rev. C. V. V., on mountain limestone fossils, 148 Harlbucht, its bay formed in the 16th century, 331 Hartsoeker, on the quantity of sediment in the waters of the Rhine, 282 Hartz, Werner on the granite of the, 65 Harwich, rapid decay of the cliffs at, 3 1 4 - will probably soon become an island, 314 Heat, laws which govern the diffusion of, 121 Heber, Bishop, on the animals inhabiting the Himalaya mountains, 112 Hecla, Banks and others on the colum- nar basalt of, 67 length of some of its eruptions, 426 Helice and Bura, submerged beneath the sea by an earthquake, 370 Heligoland destroyed by the sea, 330 Henderson, on the eruption of Skaptar Jokul, 1783, 426 Herculaneum and Pompeii, silence of contemporary historians concern- ing, 382 and Pompeii, how destroyed, 400 and Pompeii, reflections on the bu- ried cities of, 411 Herculaneum, thickness and composition of the mass covering, 403 was a sea-port, 404 discovered accidentally, 405 i . . its former dimensions not yet known, 405 Herculaneum, but a slight part of open for inspection, 405 objects preserved in, 406 stalactite formed in the galleries of, 405 inscriptions on the temples at, 405 rolls of papyri, still legible, found in, 408 Herodotus, on the delta of the Nile, 272 on the country round Memphis, 273 on the formation of Egypt by the Nile, 273 on the time which the Nile might require to fill up the Arabian Gulf, 273 Hewett, Capt., on the currents in the Pentland Firth, 295 on the great banks in the North Sea, 350 Hibbert, Dr., on the drifting of rock masses by the sea in Shetland islands, 297 on the effect of lightning on the rocks of Fetlar, 298 his account of the Grind of the Navir in Shetland, 299 Hiera, new island in the Gulf of Santo- rin, 441 Hillswicks Ness, action of the sea on the granitic rocks of, see wood-cut No. 10, 301 Himalaya mountains, Bishop Heber on the animals inhabiting the, 112 height of perpetual snow on the, 141 Hindoo cosmogony, 6 Hiudostan subject to earthquakes. 372 History and Geology compared, 2 Hoff, on the changes in the level of the Caspian, 25 his remarks on the persecution of Omar, 25 on the formation of marble by springs near Lake Urmia, 242 on encroachments of the sea in North America, 333 on the encroachments of the sea in the Baltic, 336 on earthquakes in Syria and Judea, 369 on the buried city of Oojain, 468 Hoffmann, M., on the new island in the Mediterranean, 453 Holbach. his theory, 1753, 46 Holland, inroads of the sea in, 328 towns destroyed by the sea in, 329 its coast probably more protected once, 332 Hollmann, hypothesis of, 1753, 55 Holm sand, account of, 311 Homer, gain of land on the coast of ligypt known to, 272 1 on the distance of Pharos from Egypt, 272 568 INDEX. Hooke, his ' Discourse of Earthquakes,' 1688 to 1703, 36 011 local distribution of species, 37 on extinct species, 37 on duration of species, 38 contends that fossils are not { lusus naturae,' 38 on modes of lapidification, 38 . on simultaneous extent of earth- quakes, 39 on the deluge, 39 on the elevation of the coast of Chili, 509 on the earthquake of Java in 1699, 511 - on the elevation of the coast of the Bay of Baiae, 528 Hooker, Dr., accounts of the eruption of Skaptar Jokul confirmed by, 426 his view of the crater of the great geyser, see wood-cut No. 32, 536 Hordwell, loss of laud at, 321 Hornitos, on Jorullo, account of, 433 Horsfield, Dr., on earthquake of 1786, in Java, 474 his account of the eruption of Pa- pandayang in Java/503 Horsburgh, Capt., on icebergs in low latitudes, 128 on the advance of the Garigetic delta, 277 Humber, stratification of the warp of the, 291 encroachment of the sea in its es- tuary, 303 Humboldt, Baron, on Indian rites after the earthquake of 1766, 9 on the occurrence of the Bengal tiger in Siberia, 113 on the laws governing the distribu- tion of plants, 116 on the laws which regulate the diffusion of heat, 121 on isothermal lines, 122 on the distribution of ferns, 129 on the irregular distribution of land and sea, 139 on the transportation of sediment hy currents, 354 on the eruption of Jorullo, 432 his theory to account for the con- vexity of the plain of Malpais,432 his theory of elevation craters con- sidered, 442 his account of the earthquake of Caraccas, 1812, 469 on the earthquake in Quito in 1 797, 473 on the earthquake in Cumana, 473 on the earthquake in the Caraccas, 1790, 473 - on earthquakes in the Japan isles, 474 Humboldt, his account of the volcanic eruption in Teneriffe, 511 Hungary, art of mining, how taught in> 63 Hunstanton, its cliffs undermined, 306 Hurst Castle shingle bank, 320 Hutchins, his account of a landslip in Dorsetshire, 322 Hutchinson, John, his ' Moses's Prin- cipia,' 1724, 45 ridicules Woodward's theory, 45 objects to Newton's theory of gra- vitation,