7. UPPER EOCENE.

BRITISH. Bembridge fluvio-marine strata. (Chapter 16.) Osborne or St. Helen's series. (Chapter 16.) Headon series, with marine and fresh-water shells. (Chapter 16.) Barton sands and clays (Chapter 16.)

FOREIGN. Gypsum of Montmartre, fresh-water with Palaeotherium. (Chapter 16.) Calcaire silicieux, or Travertin inferieur. (Chapter 16.) Gres de Beauchamp, or Sables moyens. (Chapter 16.)

8. MIDDLE EOCENE.

BRITISH. Bracklesham beds and Bagshot sands. (Chapter 16.) White clays of Alum Bay and Bournemouth. (Chapter 16.)

FOREIGN. Calcaire grossier, miliolitic limestone. (Chapter 16.) Soissonnais sands, or Lits coquilliers, with Nummulites planulata. (Chapter 16.) Claiborne beds of the United States, with Orbitoides and Zeuglodon. (Chapter 16.)

9. LOWER EOCENE.

Nummulitic formation of Europe, Asia, etc. (Chapter 16.)

BRITISH. London Clay proper. (Chapter 16.) Woolwich and Reading series, fluvio-marine. (Chapter 16.) Thanet sands. (Chapter 16.)

FOREIGN. Argile de Londres, near Dunkirk. (Chapter 16.) Argile plastique. (Chapter 16.) Sables de Bracheux. (Chapter 16.)

SECONDARY OR MESOZOIC.

CRETACEOUS.

10. UPPER CRETACEOUS.

BRITISH. Upper white chalk, with flints. (Chapter 17.) Lower white chalk, without flints. (Chapter 17.) Chalk marl. (Chapter 17.) Chloritic series (or Upper Greensand), fire-stone of Surrey. (Chapter 17.) Gault. (Chapter 17.) Blackdown beds. (Chapter 17.)

FOREIGN. Maestricht beds and Faxoe chalk. (Chapter 17.) Pisolitic limestone of France. (Chapter 17.) White chalk of France, Sweden, and Russia. (Chapter 17.) Planer-kalk of Saxony. (Chapter 17.) Sands and clays of Aix-la-Chapelle. (Chapter 17.) Hippurite limestone of South of France. (Chapter 17.) New Jersey, U.S., sands and marls. (Chapter 17.)

11. LOWER CRETACEOUS OR NEOCOMIAN.

BRITISH. Sands of Folkestone, Sandgate, and Hythe. (Chapter 18.) Atherfield clay, with Perna mulleti. (Chapter 18.) Punfield marine beds, with Vicarya lujana. (Chapter 18.) Speeton clay of Flamborough Head and Tealby. (Chapter 18.) Weald clay of Surrey, Kent, and Sussex, fresh-water, with Cypris. (Chapter 18.) Hastings sands.

FOREIGN. Neocomian of Neufchatel, and Hils conglomerate of North Germany. (Chapter 18.) Wealden beds of Hanover. (Chapter 18.)

OOLITE.

12. UPPER OOLITE.

BRITISH. Upper Purbeck beds, fresh-water. (Chapter 19.) Middle Purbeck, with numerous marsupial quadrupeds, etc. (Chapter 19.) Lower Purbeck, fresh-water, with intercalated dirt-bed. (Chapter 19.) Portland stone and sand. (Chapter 19.) Kimmeridge clay. (Chapter 19.)

FOREIGN. Marnes a gryphees virgules of Argonne. (Chapter 19.) Lithographic-stone of Solenhofen, with Archaeopteryx. (Chapter 19.)

13. MIDDLE OOLITE.

BRITISH. Coral rag of Berkshire, Wilts, and Yorkshire. (Chapter 19.) Oxford clay, with belemnites and Ammonite. (Chapter 19.) Kelloway rock of Wilts and Yorkshire. (Chapter 19.)

FOREIGN. Nerinaean limestone of the Jura.

14. LOWER OOLITE.

BRITISH. Cornbrash and forest marble. (Chapter 19.) Great or Bath oolite of Bradford. (Chapter 19.) Stonesfield slate, with marsupials and Araucaria. (Chapter 19.) Fuller's earth of Bath. (Chapter 19.) Inferior oolite. (Chapter 19.)

LIAS.

15. LIAS.

Upper Lias, argillaceous, with Ammonites striatulus. (Chapter 20.) Shale and limestone, with Ammonites bifrons. (Chapter 20.) Middle Lias or Marlstone series, with zones containing characteristic Ammonites. (Chapter 20.) Lower Lias, also with zones characterised by peculiar Ammonites. (Chapter 20.)

TRIAS.

16. UPPER TRIAS.

BRITISH. Rhaetic, Penarth or Avicula contorta beds (beds of passage). (Chapter 21.) Keuper or Upper New Red sandstone, etc. (Chapter 21.) Red shales of Cheshire and Lancashire, with rock-salt. (Chapter 21.) Dolomite conglomerate of Bristol (Chapter 21.)

FOREIGN. Keuper beds of Germany. (Chapter 21.) St. Cassian or Hallstadt beds, with rich marine fauna. (Chapter 21.) Coal-field of Richmond, Virginia. (Chapter 21.) Chatham coal-field, North Carolina. (Chapter 21.)

17. MIDDLE TRIAS.

BRITISH. Wanting.

FOREIGN. Muschelkalk of Germany. (Chapter 21.)

18. LOWER TRIAS.

BRITISH. Bunter or Lower New Red sandstone of Lancashire and Cheshire. (Chapter 21.)

FOREIGN. Bunter-sandstein of Germany. (Chapter 21.) Red sandstone of Connecticut Valley, with footprints of birds and reptiles. (Chapter 21.)

PRIMARY OR PALAEOZOIC.

PERMIAN.

19. PERMIAN.

BRITISH. Upper Permian of St. Bees' Head, Cumberland. (Chapter 22.) Middle Permian, magnesian limestone, and marl-slate of Durham and Yorkshire, with Protosaurus. (Chapter 22.) Lower Permian sandstones and breccias of Penrith and Dumfriesshire, intercalated. (Chapter 22.)

FOREIGN. Dark-coloured shales of Thuringia. (Chapter 22.) Zechstein or Dolomitic limestone. (Chapter 22.) Mergel-schiefer or Kupfer-schiefer. (Chapter 22.) Rothliegendes of Thuringia, with Psaronius. (Chapter 22.) Magnesian limestones, etc., of Russia. (Chapter 22.)

CARBONIFEROUS.

20. UPPER CARBONIFEROUS.

BRITISH. Coal-measures of South Wales, with underclays inclosing Stigmaria. (Chapter 23.) Coal-measures of north and central England. (Chapter 23.) Millstone grit. (Chapter 23.) Yoredale series of Yorkshire. (Chapter 23.) Coal-field of Kilkenny with Labyrinthodont. (Chapter 23.)

FOREIGN. Coal-field of Saarbruck, with Archegosaurus. (Chapter 23.) Carboniferous strata of South Joggins, Nova Scotia. (Chapter 23.) Pennsylvania coal-field. (Chapter 23.)

21. LOWER CARBONIFEROUS.

BRITISH. Mountain limestone of Wales and South of England. (Chapter 24.) Same in Ireland. (Chapter 24.) Carboniferous limestone of Scotland alternating with coal-bearing sandstones. (Chapter 23.) Erect trees in volcanic ash in the Island of Arran. (Chapter 30.)

FOREIGN. Mountain limestone of Belgium. (Chapter 24.)

DEVONIAN OR OLD RED SANDSTONE.

22. UPPER DEVONIAN.

BRITISH. Yellow sandstone of Dura Den, with Holoptychius, etc. (Chapter 25.); and of Ireland with Anodon Jukesii. (Chapter 25.) Sandstones of Forfarshire and Perthshire, with Holoptychius, etc. (Chapter 25.) Pilton group of North Devon. (Chapter 25.) Petherwyn group of Cornwall, with Clymenia and Cypridina. (Chapter 25.)

FOREIGN. Clymenien-kalk and Cypridinen-schiefer of Germany. (Chapter 25.)

23. MIDDLE DEVONIAN.

BRITISH. Bituminous schists of Gamrie, Caithness, etc., with numerous fish. (Chapter 25.) Ilfracombe beds with peculiar trilobites and corals. (Chapter 25.) Limestones of Torquay, with broad-winged Spirifers. (Chapter 25.)

FOREIGN. (Chapter 25.) Eifel limestone, with underlying schists containing Calceola. (Chapter 25.) Devonian strata of Russia. (Chapter 25.)

24. LOWER DEVONIAN.

BRITISH. Arbroath paving-stones, with Cephalaspis and Pterygotus. (Chapter 25.) Lower sandstones of Forfarshire, with Pterygotus. (Chapter 25.) Sandstones and slates of the Foreland and Linton. (Chapter 25.)

FOREIGN. Oriskany sandstone of Western Canada and New York. (Chapter 25.) Sandstones of Gaspe, with Cephalaspis. (Chapter 25.)

SILURIAN.

25. UPPER SILURIAN.

BRITISH. Upper Ludlow formation, Downton sandstone, with bone-bed. (Chapter 26.) Lower Ludlow formation, with oldest known fish remains. (Chapter 26.) Wenlock limestone and shale. (Chapter 26.) Woolhope limestone and grit. (Chapter 26.) Tarannon shales. (Chapter 26.) Beds of passage between Upper and Lower Silurian: Upper Llandovery, or May-hill sandstone, with Pentamerus oblongus, etc. (Chapter 26.) Lower Llandovery slates. (Chapter 26.)

FOREIGN. Niagara limestone, with Calymene, Homalonotus, etc. (Chapter 26.) Clinton group of America, with Pentamerus oblongus, etc. (Chapter 26.) Silurian strata of Russia, with Pentamerus. (Chapter 26.)

26. LOWER SILURIAN.

BRITISH. Bala and Caradoc beds. (Chapter 26.) Llandeilo flags. (Chapter 26.) Arenig or Stiper-stones group (Lower Llandeilo of Murchison.) (Chapter 26.)

FOREIGN. Ungulite or Obolus grit of Russia. (Chapter 26.) Trenton limestone, and other Lower Silurian groups of North America. (Chapter 26.) Lower Silurian of Sweden. (Chapter 26.)

CAMBRIAN.

27. UPPER CAMBRIAN.

BRITISH. Tremadoc slates. (Chapter 27.) Lingula flags, with Lingula Davisii. (Chapter 27.)

FOREIGN. "Primordial" zone of Bohemia in part, with trilobites of the genera Paradoxides, etc. (Chapter 27.) Alum schists of Sweden and Norway. (Chapter 27.) Potsdam sandstone, with Dikelocephalus and Obolella. (Chapter 27.)

28. LOWER CAMBRIAN.

BRITISH. Menevian beds of Wales, with Paradoxides Davidis, etc. (Chapter 27.) Longmynd group, comprising the Harlech grits and Llanberis slates. (Chapter 27.)

FOREIGN. Lower portion of Barrande's "Primordial" zone in Bohemia. (Chapter 27.) Fucoid sandstones of Sweden. (Chapter 27.) Huronian series of Canada? (Chapter 27.)

LAURENTIAN.

29. UPPER LAURENTIAN.

BRITISH. Fundamental gneiss of the Hebrides? (Chapter 27.) Hypersthene rocks of Skye? (Chapter 27.)

FOREIGN. Labradorite series north of the river St. Lawrence in Canada. (Chapter 27.) Adirondack mountains of New York. (Chapter 27.)

30. LOWER LAURENTIAN.

BRITISH. Wanting?

FOREIGN. Beds of gneiss and quartzite, with interstratified limestones, in one of which, 1000 feet thick, occurs a foraminifer, Eozoon Canadense, the oldest known fossil. (Chapter 27.)

CHAPTER IX.

CLASSIFICATION OF TERTIARY FORMATIONS.

Order of Succession of Sedimentary Formations. Frequent Unconformability of Strata. Imperfection of the Record. Defectiveness of the Monuments greater in Proportion to their Antiquity. Reasons for studying the newer Groups first. Nomenclature of Formations. Detached Tertiary Formations scattered over Europe. Value of the Shell-bearing Mollusca in Classification. Classification of Tertiary Strata. Eocene, Miocene, and Pliocene Terms explained.

By reference to the tables given at the end of the last chapter the reader will see that when the fossiliferous rocks are arranged chronologically, we have first to consider the Post-tertiary and then the Tertiary or Cainozoic formations, and afterwards to pass on to those of older date.

ORDER OF SUPERPOSITION.

(FIGURE 86. Section through Primary (left), Secondary, Tertiary and Post- tertiary (right) Strata. 1. Laurentian. 2. Cambrian. 3. Silurian. 4. Devonian. 5. Carboniferous. 6. Permian. 7. Triassic. 8. Jurassic. 9. Cretaceous. 10. Eocene. 11. Miocene. 12. Pliocene. 13. Post-pliocene. 14. Recent. Sea.)

The diagram (Figure 86.) will show the order of superposition of these deposits, assuming them all to be visible in one continuous section. In nature, as before hinted (Chapter 6), we have never an opportunity of seeing the whole of them so displayed in a single region; first, because sedimentary deposition is confined, during any one geological period, to limited areas; and secondly, because strata, after they have been formed, are liable to be utterly annihilated over wide areas by denudation. But wherever certain members of the series are present, they overlie one another in the order indicated in the diagram, though not always in the exact manner there represented, because some of them repose occasionally in unconformable stratification on others. This mode of superposition has been already explained (Chapters 5 and 7), where I pointed out that the discordance which implies a considerable lapse of time between two formations in juxtaposition is almost invariably accompanied by a great dissimilarity in the species of organic remains.

FREQUENT UNCONFORMABILITY OF STRATA.

Where the widest gaps appear in the sequence of the fossil forms, as between the Permian and Triassic rocks, or between the Cretaceous and Eocene, examples of such unconformability are very frequent. But they are also met with in some part or other of the world at the junction of almost all the other principal formations, and sometimes the subordinate divisions of any one of the leading groups may be found lying unconformably on another subordinate member of the same— the Upper, for example, on the Lower Silurian, or the superior division of the Old Red Sandstone on a lower member of the same, and so forth. Instances of such irregularities in the mode of succession of the strata are the more intelligible the more we extend our survey of the fossiliferous formations, for we are continually bringing to light deposits of intermediate date, which have to be intercalated between those previously known, and which reveal to us a long series of events, of which antecedently to such discoveries we had no knowledge.

But while unconformability invariably bears testimony to a lapse of unrepresented time, the conformability of two sets of strata in contact by no means implies that the newer formation immediately succeeded the older one. It simply implies that the ancient rocks were subjected to no movements of such a nature as to tilt, bend, or break them before the more modern formation was superimposed. It does not show that the earth's crust was motionless in the region in question, for there may have been a gradual sinking or rising, extending uniformly over a large surface, and yet, during such movement, the stratified rocks may have retained their original horizontality of position. There may have been a conversion of a wide area from sea into land and from land into sea, and during these changes of level some strata may have been slowly removed by aqueous action, and after this new strata may be superimposed, differing perhaps in date by thousands of years or centuries, and yet resting conformably on the older set. There may even be a blending of the materials constituting the older deposit with those of the newer, so as to give rise to a passage in the mineral character of the one rock into the other as if there had been no break or interruption in the depositing process.

IMPERFECTION OF THE RECORD.

Although by the frequent discovery of new sets of intermediate strata the transition from one type of organic remains to another is becoming less and less abrupt, yet the entire series of records appears to the geologists now living far more fragmentary and defective than it seemed to their predecessors half a century ago. The earlier inquirers, as often as they encountered a break in the regular sequence of formations, connected it theoretically with a sudden and violent catastrophe, which had put an end to the regular course of events that had been going on uninterruptedly for ages, annihilating at the same time all or nearly all the organic beings which had previously flourished, after which, order being re-established, a new series of events was initiated. In proportion as our faith in these views grows weaker, and the phenomena of the organic or inorganic world presented to us by geology seem explicable on the hypothesis of gradual and insensible changes, varied only by occasional convulsions, on a scale comparable to that witnessed in historical times; and in proportion as it is thought possible that former fluctuations in the organic world may be due to the indefinite modifiability of species without the necessity of assuming new and independent acts of creation, the number and magnitude of the gaps which still remain, or the extreme imperfection of the record, become more and more striking, and what we possess of the ancient annals of the earth's history appears as nothing when contrasted with that which has been lost.

When we examine a large area such as Europe, the average as well as the extreme height above the sea attained by the older formations is usually found to exceed that reached by the more modern ones, the primary or palaeozoic rising higher than the secondary, and these in their turn than the tertiary; while in reference to the three divisions of the tertiary, the lowest or Eocene group attains a higher summit-level than the Miocene, and these again a greater height than the Pliocene formations. Lastly, the post-tertiary deposits, such, at least, as are of marine origin, are most commonly restricted to much more moderate elevations above the sea-level than the tertiary strata.

It is also observed that strata, in proportion as they are of newer date, bear the nearest resemblance in mineral character to those which are now in the progress of formation in seas or lakes, the newest of all consisting principally of soft mud or loose sand, in some places full of shells, corals, or other organic bodies, animal or vegetable, in others wholly devoid of such remains. The farther we recede from the present time, and the higher the antiquity of the formations which we examine, the greater are the changes which the sedimentary deposits have undergone. Time, as I have explained in Chapters 5, 6, and 7, has multiplied the effects of condensation by pressure and cementation, and the modification produced by heat, fracture, contortion, upheaval, and denudation. The organic remains also have sometimes been obliterated entirely, or the mineral matter of which they were composed has been removed and replaced by other substances.

WHY NEWER GROUPS SHOULD BE STUDIED FIRST.

We likewise observe that the older the rocks the more widely do their organic remains depart from the types of the living creation. First, we find in the newer tertiary rocks a few species which no longer exist, mixed with many living ones, and then, as we go farther back, many genera and families at present unknown make their appearance, until we come to strata in which the fossil relics of existing species are nowhere to be detected, except a few of the lowest forms of invertebrate, while some orders of animals and plants wholly unrepresented in the living world begin to be conspicuous.

When we study, therefore, the geological records of the earth and its inhabitants, we find, as in human history, the defectiveness and obscurity of the monuments always increasing the remoter the era to which we refer, and the difficulty of determining the true chronological relations of rocks is more and more enhanced, especially when we are comparing those which were formed simultaneously in very distant regions of the globe. Hence we advance with securer steps when we begin with the study of the geological records of later times, proceeding from the newer to the older, or from the more to the less known.

In thus inverting what might at first seem to be the more natural order of historical research, we must bear in mind that each of the periods above enumerated, even the shortest, such as the Post-tertiary, or the Pliocene, Miocene, or Eocene, embrace a succession of events of vast extent, so that to give a satisfactory account of what we already know of any one of them would require many volumes. When, therefore, we approach one of the newer groups before endeavouring to decipher the monuments of an older one, it is like endeavouring to master the history of our own country and that of some contemporary nations, before we enter upon Roman History, or like investigating the annals of Ancient Italy and Greece before we approach those of Egypt and Assyria.

NOMENCLATURE.

The origin of the terms Primary and Secondary, and the synonymous terms Palaeozoic, and Mesozoic, were explained in Chapter 8.

The Tertiary or Cainozoic strata (see Chapter 8) were so called because they were all posterior in date to the Secondary series, of which last the Chalk of Cretaceous, No. 9, Figure 86, constitutes the newest group. The whole of them were at first confounded with the superficial alluviums of Europe; and it was long before their real extent and thickness, and the various ages to which they belong, were fully recognised. They were observed to occur in patches, some of fresh-water, others of marine origin, their geographical area being usually small as compared to the secondary formations, and their position often suggesting the idea of their having been deposited in different bays, lakes, estuaries, or inland seas, after a large portion of the space now occupied by Europe had already been converted into dry land.

The first deposits of this class, of which the characters were accurately determined, were those occurring in the neighbourhood of Paris, described in 1810 by MM. Cuvier and Brongniart. They were ascertained to consist of successive sets of strata, some of marine, others of fresh-water origin, lying one upon the other. The fossil shells and corals were perceived to be almost all of unknown species, and to have in general a near affinity to those now inhabiting warmer seas. The bones and skeletons of land animals, some of them of large size, and belonging to more than forty distinct species, were examined by Cuvier, and declared by him not to agree specifically, nor most of them even generically, with any hitherto observed in the living creation.

Strata were soon afterwards brought to light in the vicinity of London, and in Hampshire, which, although dissimilar in mineral composition, were justly inferred by Mr. T. Webster to be of the same age as those of Paris, because the greater number of the fossil shells were specifically identical. For the same reason, rocks found on the Gironde, in the South of France, and at certain points in the North of Italy, were suspected to be of contemporaneous origin.

Another important discovery was soon afterwards made by Brocchi in Italy, who investigated the argillaceous and sandy deposits, replete with shells, which form a low range of hills, flanking the Apennines on both sides, from the plains of the Po to Calabria. These lower hills were called by him the Subapennines, and were formed of strata chiefly marine, and newer than those of Paris and London.

Another tertiary group occurring in the neighbourhood of Bordeaux and Dax, in the South of France, was examined by M. de Basterot in 1825, who described and figured several hundred species of shells, which differed for the most part both from the Parisian series and those of the Subapennine hills. It was soon, therefore, suspected that this fauna might belong to a period intermediate between that of the Parisian and Subapennine strata, and it was not long before the evidence of superposition was brought to bear in support of this opinion; for other strata, contemporaneous with those of Bordeaux, were observed in one district (the Valley of the Loire), to overlie the Parisian formation, and in another (in Piedmont) to underlie the Subapennine beds. The first example of these was pointed out in 1829 by M. Desnoyers, who ascertained that the sand and marl of marine origin called faluns, near Tours, in the basin of the Loire, full of sea-shells and corals, rested upon a lacustrine formation, which constitutes the uppermost subdivision of the Parisian group, extending continuously throughout a great table-land intervening between the basin of the Seine and that of the Loire. The other example occurs in Italy, where strata containing many fossils similar to those of Bordeaux were observed by Bonelli and others in the environs of Turin, subjacent to strata belonging to the Subapennine group of Brocchi.

VALUE OF TESTACEAN FOSSILS IN CLASSIFICATION.

It will be observed that in the foregoing allusions to organic remains, the testacea or the shell-bearing mollusca are selected as the most useful and convenient class for the purposes of general classification. In the first place, they are more universally distributed through strata of every age than any other organic bodies. Those families of fossils which are of rare and casual occurrence are absolutely of no avail in establishing a chronological arrangement. If we have plants alone in one group of strata and the bones of mammalia in another, we can draw no conclusion respecting the affinity or discordance of the organic beings of the two epochs compared; and the same may be said if we have plants and vertebrated animals in one series and only shells in another. Although corals are more abundant, in a fossil state, than plants, reptiles, or fish, they are still rare when contrasted with shells, because they are more dependent for their well-being on the constant clearness of the water, and are, therefore, less likely to be included in rocks which endure in consequence of their thickness and the copiousness of sediment which prevailed when they originated. The utility of the testacea is, moreover, enhanced by the circumstance that some forms are proper to the sea, others to the land, and others to fresh water. Rivers scarcely ever fail to carry down into their deltas some land-shells, together with species which are at once fluviatile and lacustrine. By this means we learn what terrestrial, fresh-water, and marine species coexisted at particular eras of the past: and having thus identified strata formed in seas with others which originated contemporaneously in inland lakes, we are then enabled to advance a step farther, and show that certain quadrupeds or aquatic plants, found fossil in lacustrine formations, inhabited the globe at the same period when certain fish, reptiles, and zoophytes lived in the ocean.

Among other characters of the molluscous animals, which render them extremely valuable in settling chronological questions in geology, may be mentioned, first, the wide geographical range of many species; and, secondly, what is probably a consequence of the former, the great duration of species in this class, for they appear to have surpassed in longevity the greater number of the mammalia and fish. Had each species inhabited a very limited space, it could never, when imbedded in strata, have enabled the geologist to identify deposits at distant points; or had they each lasted but for a brief period, they could have thrown no light on the connection of rocks placed far from each other in the chronological, or, as it is often termed, vertical series.

CLASSIFICATION OF TERTIARY STRATA.

Many authors have divided the European Tertiary strata into three groups— lower, middle, and upper; the lower comprising the oldest formations of Paris and London before mentioned; the middle those of Bordeaux and Touraine; and the upper all those newer than the middle group.

In the first edition of the Principles of Geology, I divided the whole of the Tertiary formations into four groups, characterised by the percentage of recent shells which they contained. The lower tertiary strata of London and Paris were thought by M. Deshayes to contain only 3 1/2 per cent of recent species, and were termed Eocene. The middle tertiary of the Loire and Gironde had, according to the specific determinations of the same conchologist, 17 per cent, and formed the Miocene division. The Subapennine beds contained 35 to 50 per cent, and were termed Older Pliocene, while still more recent beds in Sicily, which had from 90 to 95 per cent of species identical with those now living, were called Newer Pliocene. The first of the above terms, Eocene, is derived from eos, dawn, and cainos, recent, because the fossil shells of this period contain an extremely small proportion of living species, which may be looked upon as indicating the dawn of the existing state of the testaceous fauna, no recent species having been detected in the older or secondary rocks.

The term Miocene (from meion, less, and cainos, recent) is intended to express a minor proportion of recent species (of testacea), the term Pliocene (from pleion, more, and cainos, recent) a comparative plurality of the same. It may assist the memory of students to remind them, that the MI-ocene contain a MI-nor proportion, and PL-iocene a comparative PL-urality of recent species; and that the greater number of recent species always implies the more modern origin of the strata.

It has sometimes been objected to this nomenclature that certain species of infusoria found in the chalk are still existing, and, on the other hand, the Miocene and Older Pliocene deposits often contain the remains of mammalia, reptiles, and fish, exclusively of extinct species. But the reader must bear in mind that the terms Eocene, Miocene, and Pliocene were originally invented with reference purely to conchological data, and in that sense have always been and are still used by me.

Since the year 1830 the number of known shells, both recent and fossil, has largely increased, and their identification has been more accurately determined. Hence some modifications have been required in the classifications founded on less perfect materials. The Eocene, Miocene, and Pliocene periods have been made to comprehend certain sets of strata of which the fossils do not always conform strictly in the proportion of recent to extinct species with the definitions first given by me, or which are implied in the etymology of those terms.

CHAPTER X.

RECENT AND POST-PLIOCENE PERIODS.

Recent and Post-pliocene Periods. Terms defined. Formations of the Recent Period. Modern littoral Deposits containing Works of Art near Naples. Danish Peat and Shell-mounds. Swiss Lake-dwellings. Periods of Stone, Bronze, and Iron. Post-pliocene Formations. Coexistence of Man with extinct Mammalia. Reindeer Period of South of France. Alluvial Deposits of Paleolithic Age. Higher and Lower-level Valley-gravels. Loess or Inundation-mud of the Nile, Rhine, etc. Origin of Caverns. Remains of Man and extinct Quadrupeds in Cavern Deposits. Cave of Kirkdale. Australian Cave-breccias. Geographical Relationship of the Provinces of living Vertebrata and those of extinct Post-pliocene Species. Extinct struthious Birds of New Zealand. Climate of the Post-pliocene Period. Comparative Longevity of Species in the Mammalia and Testacea. Teeth of Recent and Post-pliocene Mammalia.

We have seen in the last chapter that the uppermost or newest strata are called Post-tertiary, as being more modern than the Tertiary. It will also be observed that the Post-tertiary formations are divided into two subordinate groups: the Recent, and Post-pliocene. In the former, or the Recent, the mammalia as well as the shells are identical with species now living: whereas in the Post-pliocene, the shells being all of living forms, a part, and often a considerable part, of the mammalia belonged to extinct species. To this nomenclature it may be objected that the term Post-pliocene should in strictness include all geological monuments posterior in date to the Pliocene; but when I have occasion to speak of the whole collectively, I shall call them Post-tertiary, and reserve the term Post-pliocene for the older Post-tertiary formations, while the Upper or newer ones will be called "Recent."

Cases will occur where it may be scarcely possible to draw the boundary line between the Recent and Post-pliocene deposits; and we must expect these difficulties to increase rather than diminish with every advance in our knowledge, and in proportion as gaps are filled up in the series of records.

RECENT PERIOD.

It was stated in the sixth chapter, when I treated of denudation, that the dry land, or that part of the earth's surface which is not covered by the waters of lakes or seas, is generally wasting away by the incessant action of rain and rivers, and in some cases by the undermining and removing power of waves and tides on the sea-coast. But the rate of waste is very unequal, since the level and gently sloping lands, where they are protected by a continuous covering of vegetation, escape nearly all wear and tear, so that they may remain for ages in a stationary condition, while the removal of matter is constantly widening and deepening the intervening ravines and valleys.

The materials, both fine and coarse, carried down annually by rivers from the higher regions to the lower, and deposited in successive strata in the basins of seas and lakes, must be of enormous volume. We are always liable to underrate their magnitude, because the accumulation of strata is going on out of sight.

There are, however, causes at work which, in the course of centuries, tend to render visible these modern formations, whether of marine or lacustrine origin. For a large portion of the earth's crust is always undergoing a change of level, some areas rising and others sinking at the rate of a few inches, or a few feet, perhaps sometimes yards, in a century; so that spaces which were once subaqueous are gradually converted into land, and others which were high and dry become submerged. In consequence of such movements we find in certain regions, as in Cashmere, for example, where the mountains are often shaken by earthquakes, deposits which were formed in lakes in the historical period, but through which rivers have now cut deep and wide channels. In lacustrine strata thus intersected, works of art and fresh-water shells are seen. In other districts on the borders of the sea, usually at very moderate elevations above its level, raised beaches occur, or marine littoral deposits, such as those in which, on the borders of the Bay of Baiae, near Naples, the well-known temple of Serapis was imbedded. In that case the date of the monument buried in the marine strata is ascertainable, but in many other instances the exact age of the remains of human workmanship is uncertain, as in the estuary of the Clyde at Glasgow, where many canoes have been exhumed, with other works of art, all assignable to some part of the Recent Period.

DANISH PEAT AND SHELL-MOUNDS OR KITCHEN-MIDDENS.

Sometimes we obtain evidence, without the aid of a change of level, of events which took place in pre-historic times. The combined labours, for example, of the antiquary, zoologist, and botanist have brought to light many monuments of the early inhabitants buried in peat-mosses in Denmark. Their geological age is determined by the fact that, not only the contemporaneous fresh-water and land shells, but all the quadrupeds, found in the peat, agree specifically with those now inhabiting the same districts, or which are known to have been indigenous in Denmark within the memory of man. In the lower beds of peat (a deposit varying from 20 to 30 feet in thickness), weapons of stone accompany trunks of the Scotch fir, Pinus sylvestris. This peat may be referred to that part of the stone period for which Sir John Lubbock proposed the name of "Neolithic" in contradistinction to a still older era, termed by him "Paleolithic," and which will be described in the sequel. (Sir John Lubbock Pre-historic Times page 3 1865.) In the higher portions of the same Danish bogs, bronze implements are associated with trunks and acorns of the common oak. It appears that the pine has never been a native of Denmark in historical times, and it seems to have given place to the oak about the time when articles and instruments of bronze superseded those of stone. It also appears that, at a still later period, the oak itself became scarce, and was nearly supplanted by the beech, a tree which now flourishes luxuriantly in Denmark. Again, at the still later epoch when the beech-tree abounded, tools of iron were introduced, and were gradually substituted for those of bronze.

On the coasts of the Danish islands in the Baltic, certain mounds, called in those countries "Kjokken-modding," or "kitchen-middens," occur, consisting chiefly of the castaway shells of the oyster, cockle, periwinkle, and other eatable kinds of molluscs. The mounds are from three to ten feet high, and from 100 to 1000 feet in their longest diameter. They greatly resemble heaps of shells formed by the Red Indians of North America along the eastern shores of the United States. In the old refuse-heaps, recently studied by the Danish antiquaries and naturalists with great skill and diligence, no implements of metal have ever been detected. All the knives, hatchets, and other tools, are of stone, horn, bone, or wood. With them are often intermixed fragments of rude pottery, charcoal and cinders, and the bones of quadrupeds on which the rude people fed. These bones belong to wild species still living in Europe, though some of them, like the beaver, have long been extirpated in Denmark. The only animal which they seem to have domesticated was the dog.

As there is an entire absence of metallic tools, these refuse-heaps are referred to the Neolithic division of the age of stone, which immediately preceded in Denmark the age of bronze. It appears that a race more advanced in civilisation, armed with weapons of that mixed metal, invaded Scandinavia, and ousted the aborigines.

LACUSTRINE HABITATIONS OF SWITZERLAND.

In Switzerland a different class of monuments, illustrating the successive ages of stone, bronze, and iron, has been of late years investigated with great success, and especially since 1854, in which year Dr. F. Keller explored near the shore at Meilen, in the bottom of the lake of Zurich, the ruins of an old village, originally built on numerous wooden piles, driven, at some unknown period, into the muddy bed of the lake. Since then a great many other localities, more than a hundred and fifty in all, have been detected of similar pile-dwellings, situated near the borders of the Swiss lakes, at points where the depth of water does not exceed 15 feet. (Bulletin de la Societie Vaudoise des Sciences Nat. tome 6 Lausanne 1860; and Antiquity of Man by the author chapter 2.) The superficial mud in such cases is filled with various articles, many hundreds of them being often dredged up from a very limited area. Thousands of piles, decayed at their upper extremities, are often met with still firmly fixed in the mud.

As the ages of stone, bronze, and iron merely indicate successive stages of civilisation, they may all have coexisted at once in different parts of the globe, and even in contiguous regions, among nations having little intercourse with each other. To make out, therefore, a distinct chronological series of monuments is only possible when our observations are confined to a limited district, such as Switzerland.

The relative antiquity of the pile-dwellings, which belong respectively to the ages of stone and bronze, is clearly illustrated by the associations of the tools with certain groups of animal remains. Where the tools are of stone, the castaway bones which served for the food of the ancient people are those of deer, the wild boar, and wild ox, which abounded when society was in the hunter state. But the bones of the later or bronze epoch were chiefly those of the domestic ox, goat, and pig, indicating progress in civilisation. Some villages of the stone age are of later date than others, and exhibit signs of an improved state of the arts. Among their relics are discovered carbonised grains of wheat and barley, and pieces of bread, proving that the cultivation of cereals had begun. In the same settlements, also, cloth, made of woven flax and straw, has been detected.

The pottery of the bronze age in Switzerland is of a finer texture, and more elegant in form, than that of the age of stone. At Nidau, on the lake of Bienne, articles of iron have also been discovered, so that this settlement was evidently not abandoned till that metal had come into use.

At La Thene, in the northern angle of the lake of Neufchatel, a great many articles of iron have been obtained, which in form and ornamentation are entirely different both from those of the bronze period and from those used by the Romans. Gaulish and Celtic coins have also been found there by MM. Schwab and Desor. They agree in character with remains, including many iron swords, which have been found at Tiefenau, near Berne, in ground supposed to have been a battle-field; and their date appears to have been anterior to the great Roman invasion of Northern Europe, though perhaps not long before that event. (Sir J. Lubbock's Lecture, Royal Institution February 27, 1863.) Coins, which sometimes occur in deposits of the age of iron, have never yet been found in formations of the ages of bronze or stone.

The period of bronze must have been one of foreign commerce, as tin, which enters into this metallic mixture in the proportion of about ten per cent to the copper, was obtained by the ancients chiefly from Cornwall. (Diodorus 5, 21, 22 and Sir H. James Note on Block of Tin dredged up in Falmouth Harbour. Royal Institution of Cornwall 1863.) Very few human bones of the bronze period have been met with in the Danish peat, or in the Swiss lake-dwellings, and this scarcity is generally attributed by archaeologists to the custom of burning the dead, which prevailed in the age of bronze.

POST-PLIOCENE PERIOD.

From the foregoing observations we may infer that the ages of iron and bronze in Northern and Central Europe were preceded by a stone age, the Neolithic, referable to that division of the post-tertiary epoch which I have called Recent, when the mammalia as well as the other organic remains accompanying the stone implements were of living species. But memorials have of late been brought to light of a still older age of stone, for which, as above stated, the name Paleolithic has been proposed, when man was contemporary in Europe with the elephant and rhinoceros, and various other animals, of which many of the most conspicuous have long since died out.

REINDEER PERIOD IN SOUTH OF FRANCE.

In the larger number of the caves of Europe, as for example in those of England, Belgium, Germany, and many parts of France, the animal remains agree specifically with the fauna of this oldest division of the age of stone, or that to which belongs the drift of Amiens and Abbeville presently to be mentioned, containing flint implements of a very antique type. But there are some caves in the departments of Dordogne, Aude, and other parts of the south of France, which are believed by M. Lartet to be of intermediate date between the Paleolithic and Neolithic periods. To this intermediate era M. Lartet gave, in 1863, the name of the "reindeer period," because vast quantities of the bones and horns of that deer have been met with in the French caverns. In some cases separate plates of molars of the mammoth, and several teeth of the great Irish deer, Cervus megaceros, and of the cave-lion, Felis spelaea, have been found mixed up with cut and carved bones of reindeer. On one of these sculptured bones in the cave of Perigord, a rude representation of the mammoth, with its long curved tusks and covering of wool, occurs, which is regarded by M. Lartet as placing beyond all doubt the fact that the early inhabitants of these caves must have seen this species of elephant still living in France. The presence of the marmot, as well as the reindeer and some other northern animals, in these caverns seems to imply a colder climate than that of the Swiss lake-dwellings, in which no remains of reindeer have as yet been discovered. The absence of this last in the old lacustrine habitations of Switzerland is the more significant, because in a cave in the neighbourhood of the lake of Geneva, namely, that of Mont Saleve, bones of the reindeer occur with flint implements similar to those of the caverns of Dordogne and Perigord.

The state of the arts, as exemplified by the instruments found in these caverns of the reindeer period, is somewhat more advanced than that which characterises the tools of the Amiens drift, but is nevertheless more rude than that of the Swiss lake-dwellings. No metallic articles occur, and the stone hatchets are not ground after the fashion of celts; the needles of bone are shaped in a workmanlike style, having their eyes drilled with consummate skill.

The formations above alluded to, which are as yet but imperfectly known, may be classed as belonging to the close of the Paleolithic era, of the monuments of which I am now about to treat.

ALLUVIAL DEPOSITS OF THE PALEOLITHIC AGE.

(FIGURE 87. Recent and Post-pliocene alluvial deposits. 1. Peat of the recent period. 2. Gravel of modern river. 2'. Loam of brick-earth (loess) of same age as 2, formed by inundations of the river. 3. Lower-level valley-gravel with extinct mammalia (Post-pliocene). 3'. Loam of same age. 4. Higher-level valley-gravel (Post-pliocene). 4'. Loam of same age. 5. Upland gravel of various kinds and periods, consisting in some places of unstratified boulder clay or glacial drift. 6. Older rocks.)

The alluvial and marine deposits of the Paleolithic age, the earliest to which any vestiges of man have yet been traced back, belong to a time when the physical geography of Europe differed in a marked degree from that now prevailing. In the Neolithic period, the valleys and rivers coincided almost entirely with those by which the present drainage of the land is effected, and the peat-mosses were the same as those now growing. The situation of the shell- mounds and lake-dwellings above alluded to is such as to imply that the topography of the districts where they are observed has not subsequently undergone any material alteration. Whereas we no sooner examine the Post- pliocene formations, in which the remains of so many extinct mammalia are found, than we at once perceive a more decided discrepancy between the former and present outline of the surface. Since those deposits originated, changes of considerable magnitude have been effected in the depth and width of many valleys, as also in the direction of the superficial and subterranean drainage, and, as is manifest near the sea-coast, in the relative position of land and water. In Figure 87 an ideal section is given, illustrating the different position which the Recent and Post-pliocene alluvial deposits occupy in many European valleys.

The peat, No. 1, has been formed in a low part of the modern alluvial plain, in parts of which gravel No. 2 of the recent period is seen. Over this gravel the loam or fine sediment 2' has in many places been deposited by the river during floods which covered nearly the whole alluvial plain.

No. 3 represents an older alluvium, composed of sand and gravel, formed before the valley had been excavated to its present depth. It contains the remains of fluviatile shells of living species associated with the bones of mammalia, in part of recent, and in part of extinct species. Among the latter, the mammoth (E. primigenius) and the Siberian rhinoceros (R. tichorhinus) are the most common in Europe. No. 3' is a remnant of the loam or brick-earth by which No. 3 was overspread. No. 4 is a still older and more elevated terrace, similar in its composition and organic remains to No. 3, and covered in like manner with its inundation-mud, 4'. Sometimes the valley-gravels of older date are entirely missing, or there is only one, and occasionally there are more than two, marking as many successive stages in the excavation of the valley. They usually occur at heights varying from 10 to 100 feet, sometimes on the right and sometimes on the left side of the existing river-plain, but rarely in great strength on exactly opposite sides of the valley.

Among the genera of extinct quadrupeds most frequently met with in England, France, Germany, and other parts of Europe, are the elephant, rhinoceros, hippopotamus, horse, great Irish deer, bear, tiger, and hyaena. In the peat, No. 1 (Figure 87), and in the more modern gravel and silt (No. 2), works of art of the ages of iron and bronze, and of the later or Neolithic stone period, already described, are met with. In the more ancient or Paleolithic gravels, 3 and 4, there have been found of late years in several valleys in France and England— as, for example, in those of the Seine and Somme, and of the Thames and Ouse, near Bedford— stone implements of a rude type, showing that man coexisted in those districts with the mammoth and other extinct quadrupeds of the genera above enumerated. In 1847, M. Boucher de Perthes observed in an ancient alluvium at Abbeville, in Picardy, the bones of extinct mammalia associated in such a manner with flint implements of a rude type as to lead him to infer that both the organic remains and the works of art were referable to one and the same period. This inference was soon after confirmed by Mr. Prestwich, who found in 1859 a flint tool in situ in the same stratum at Amiens that contained the remains of extinct mammalia.

The flint implements found at Abbeville and Amiens are most of them considered to be hatchets and spear-heads, and are different from those commonly called "celts." These celts, so often found in the recent formations, have a more regular oblong shape, the result of grinding, by which also a sharp edge has been given to them. The Abbeville tools found in gravel at different levels, as in Nos. 3 and 4, Figure 87, in which bones of the elephant, rhinoceros, and other extinct mammalia occur, are always unground, having evidently been brought into their present form simply by the chipping off of fragments of flint by repeated blows, such as could be given by a stone hammer.

Some of them are oval, others of a spear-headed form, no two exactly alike, and yet the greater number of each kind are obviously fashioned after the same general pattern. Their outer surface is often white, the original black flint having been discoloured and bleached by exposure to the air, or by the action of acids, as they lay in the gravel. They are most commonly stained of the same ochreous colour as the flints of the gravel in which they are imbedded. Occasionally their antiquity is indicated not only by their colour but by superficial incrustations of carbonate of lime, or by dendrites formed of oxide of iron and manganese. The edges also of most of them are worn, sometimes by having been used as tools, or sometimes by having been rolled in the old river's bed. They are met with not only in the lower-level gravels, as in No. 3, Figure 87, but also in No. 4, or the higher gravels, as at St. Acheul, in the suburbs of Amiens, where the old alluvium lies at an elevation of about 100 feet above the level of the river Somme. At both levels fluviatile and land-shells are met with in the loam as well as in the gravel, but there are no marine shells associated, except at Abbeville, in the lowest part of the gravel, near the sea, and a few feet only above the present high-water mark. Here with fossil shells of living species are mingled the bones of Elephas primigenius and E. antiquus, Rhinoceros tichorhinus, Hippopotamus, Felis spelaea, Hyaena spelaea, reindeer, and many others, the bones accompanying the flint implements in such a manner as to show that both were buried in the old alluvium at the same period.

Nearly the entire skeleton of a rhinoceros was found at one point, namely, in the Menchecourt drift at Abbeville, the bones being in such juxtaposition as to show that the cartilage must have held them together at the time of their inhumation.

The general absence here and elsewhere of human bones from gravel and sand in which flint tools are discovered, may in some degree be due to the present limited extent of our researches. But it may also be presumed that when a hunter population, always scanty in numbers, ranged over this region, they were too wary to allow themselves to be overtaken by the floods which swept away many herbivorous animals from the low river-plains where they may have been pasturing or sleeping. Beasts of prey prowling about the same alluvial flats in search of food may also have been surprised more readily than the human tenant of the same region, to whom the signs of a coming tempest were better known.

INUNDATION-MUD OF RIVERS.— BRICK-EARTH.— FLUVIATILE LOAM, OR LOESS.

As a general rule, the fluviatile alluvia of different ages (Nos. 2, 3, 4, Figure 87) are severally made up of coarse materials in their lower portions, and of fine silt or loam in their upper parts. For rivers are constantly shifting their position in the valley-plain, encroaching gradually on one bank, near which there is deep water, and deserting the other or opposite side, where the channel is growing shallower, being destined eventually to be converted into land. Where the current runs strongest, coarse gravel is swept along, and where its velocity is slackened, first sand, and then only the finest mud, is thrown down. A thin film of this fine sediment is spread, during floods, over a wide area, on one, or sometimes on both sides, of the main stream, often reaching as far as the base of the bluffs or higher grounds which bound the valley. Of such a description are the well-known annual deposits of the Nile, to which Egypt owes its fertility. So thin are they, that the aggregate amount accumulated in a century is said rarely to exceed five inches, although in the course of thousands of years it has attained a vast thickness, the bottom not having been reached by borings extending to a depth of 60 feet towards the central parts of the valley. Everywhere it consists of the same homogeneous mud, destitute of stratification— the only signs of successive accumulation being where the Nile has silted up its channel, or where the blown sands of the Libyan desert have invaded the plain, and given rise to alternate layers of sand and mud.

In European river-loams we occasionally observe isolated pebbles and angular pieces of stone which have been floated by ice to the places where they now occur; but no such coarse materials are met with in the plains of Egypt.

In some parts of the valley of the Rhine the accumulation of similar loam, called in Germany "loess," has taken place on an enormous scale. Its colour is yellowish-grey, and very homogeneous; and Professor Bischoff has ascertained, by analysis, that it agrees in composition with the mud of the Nile. Although for the most part unstratified, it betrays in some places marks of stratification, especially where it contains calcareous concretions, or in its lower part where it rests on subjacent gravel and sand which alternate with each other near the junction. About a sixth part of the whole mass is composed of carbonate of lime, and there is usually an intermixture of fine quartzose and micaceous sand.

(FIGURE 88. Succinea elongata.)

Although this loam of the Rhine is unsolidified, it usually terminates where it has been undermined by running water in a vertical cliff, from the face of which shells of terrestrial, fresh-water and amphibious mollusks project in relief. These shells do not imply the permanent sojourn of a body of fresh water on the spot, for the most aquatic of them, the Succinea, inhabits marshes and wet grassy meadows. The Succinea elongata (or S. oblongata), Figure 88, is very characteristic both of the loess of the Rhine and of some other European river- loams.

(FIGURE 89. Pupa muscorum (Linn.).)

(FIGURE 90. Helix hispida (Linn.) (plebeia).)

Among the land-shells of the Rhenish loess, Helix hispida, Figure 90, and Pupa muscorum, Figure 89, are very common. Both the terrestrial and aquatic shells are of most fragile and delicate structure, and yet they are almost invariably perfect and uninjured. They must have been broken to pieces had they been swept along by a violent inundation. Even the colour of some of the land-shells, as that of Helix nemoralis, is occasionally preserved.

In parts of the valley of the Rhine, between Bingen and Basle, the fluviatile loam or loess now under consideration is several hundred feet thick, and contains here and there throughout that thickness land and amphibious shells. As it is seen in masses fringing both sides of the great plain, and as occasionally remnants of it occur in the centre of the valley, forming hills several hundred feet in height, it seems necessary to suppose, first, a time when it slowly accumulated; and secondly, a later period, when large portions of it were removed, or when the original valley, which had been partially filled up with it, was re-excavated.

Such changes may have been brought about by a great movement of oscillation, consisting first of a general depression of the land, and then of a gradual re- elevation of the same. The amount of continental depression which first took place in the interior, must be imagined to have exceeded that of the region near the sea, in which case the higher part of the great valley would have its alluvial plain gradually raised by an accumulation of sediment, which would only cease when the subsidence of the land was at an end. If the direction of the movement was then reversed, and, during the re-elevation of the continent, the inland region nearest the mountains should rise more rapidly than that near the coast, the river would acquire a denuding power sufficient to enable it to sweep away gradually nearly all the loam and gravel with which parts of its basin had been filled up. Terraces and hillocks of mud and sand would then alone remain to attest the various levels at which the river had thrown down and afterwards removed alluvial matter.

CAVERN DEPOSITS CONTAINING HUMAN REMAINS AND BONES OF EXTINCT ANIMALS.

In England, and in almost all countries where limestone rocks abound, caverns are found, usually consisting of cavities of large dimensions, connected together by low, narrow, and sometimes torturous galleries or tunnels. These subterranean vaults are usually filled in part with mud, pebbles, and breccia, in which bones occur belonging to the same assemblage of animals as those characterising the Post-pliocene alluvia above described. Some of these bones are referable to extinct and others to living species, and they are occasionally intermingled, as in the valley-gravels, with implements of one or other of the great divisions of the stone age, and these are not unfrequently accompanied by human bones, which are much more common in cavern deposits than in valley- alluvium.

Each suite of caverns, and the passages by which they communicate the one with the other, afford memorials to the geologist of successive phases through which they must have passed. First, there was a period when the carbonate of lime was carried out gradually by springs; secondly, an era when engulfed rivers or occasional floods swept organic and inorganic debris into the subterranean hollows previously formed; and thirdly, there were such changes in the configuration of the region as caused the engulfed rivers to be turned into new channels, and springs to be dried up, after which the cave-mud, breccia, gravel, and fossil bones would bear the same kind of relation to the existing drainage of the country as the older valley-drifts with their extinct mammalian remains and works of art bear to the present rivers and alluvial plains.

The quarrying away of large masses of Carboniferous and Devonian limestone, near Liege, in Belgium, has afforded the geologist magnificent sections of some of these caverns, and the former communication of cavities in the interior of the rocks with the old surface of the country by means of vertical or oblique fissures, has been demonstrated in places where it would not otherwise have been suspected, so completely have the upper extremities of these fissures been concealed by superficial drift, while their lower ends, which extended into the roofs of the caves, are masked by stalactitic incrustations.

The origin of the stalactite is thus explained by the eminent chemist Liebig. Mould or humus, being acted on by moisture and air, evolves carbonic acid, which is dissolved by rain. The rain-water, thus impregnated, permeates the porous limestone, dissolves a portion of it, and afterwards, when the excess of carbonic acid evaporates in the caverns, parts with the calcareous matter, and forms stalactite. Even while caverns are still liable to be occasionally flooded such calcareous incrustations accumulate, but it is generally when they are no longer in the line of drainage that a solid floor of hard stalagmite is formed on the bottom.

The late Dr. Schmerling examined forty caves near Liege, and found in all of them the remains of the same fauna, comprising the mammoth, tichorhine rhinoceros, cave-bear, cave-hyaena, cave-lion, and many others, some of extinct and some of living species, and in all of them flint implements. In four or five caves only parts of human skeletons were met with, comprising sometimes skulls with a few other bones, sometimes nearly every part of the skeleton except the skull. In one of the caves, that of Engihoul, where Schmerling had found the remains of at least three human individuals, they were mingled in such a manner with bones of extinct mammalia, as to leave no doubt on his mind (in 1833) of man having co-existed with them.

In 1860, Professor Malaise, of Liege, explored with me this same cave of Engihoul, and beneath a hard floor of stalagmite we found mud full of bones of extinct and recent animals, such as Schmerling had described, and my companion, persevering in his researches after I had returned to England, extracted from the same deposit two human lower jaw-bones retaining their teeth. The skulls from these Belgian caverns display no marked deviation from the normal European type of the present day.

The careful investigations carried on by Dr. Falconer, Mr. Pengelly, and others, in the Brixham cave near Torquay, in 1858, demonstrated that flint knives were there imbedded in such a manner in loam underlying a floor of stalagmite as to prove that man had been an inhabitant of that region when the cave-bear and other members of the ancient post-pliocene fauna were also in existence.

The absence of gnawed bones had led Dr. Schmerling to infer that none of the Belgian caves which he explored had served as the dens of wild beasts; but there are many caves in Germany and England which have certainly been so inhabited, especially by the extinct hyaena and bear.

A fine example of a hyaena's den was afforded by the cave of Kirkdale, so well described by the late Dr. Buckland in his Reliquiae Diluvianae. In that cave, above twenty-five miles north-north-east of York, the remains of about 300 hyaenas, belonging to individuals of every age, were detected. The species (Hyaena spelaea) has been considered by palaeontologists as extinct; it was larger than the fierce Hyaena crocuta of South Africa, which it closely resembled, and of which it is regarded by Mr. Boyd Dawkins as a variety. Dr. Buckland, after carefully examining the spot, proved that the hyaenas must have lived there; a fact attested by the quantity of their dung, which, as in the case of the living hyaena, is of nearly the same composition as bone, and almost as durable. In the cave were found the remains of the ox, young elephant, hippopotamus, rhinoceros, horse, bear, wolf, hare, water-rat, and several birds. All the bones have the appearance of having been broken and gnawed by the teeth of the hyaenas; and they occur confusedly mixed in loam or mud, or dispersed through a crust of stalagmite which covers it. In these and many other cases it is supposed that portions of herbivorous quadrupeds have been dragged into caverns by beasts of prey, and have served as their food— an opinion quite consistent with the known habits of the living hyaena.

AUSTRALIAN CAVE-BRECCIAS.

Ossiferous breccias are not confined to Europe, but occur in all parts of the globe; and those discovered in fissures and caverns in Australia correspond closely in character with what has been called the bony breccia of the Mediterranean, in which the fragments of bone and rock are firmly bound together by a red ochreous cement.

Some of these caves were examined by the late Sir T. Mitchell in the Wellington Valley, about 210 miles west of Sidney, on the river Bell, one of the principal sources of the Macquarie, and on the Macquarie itself. The caverns often branch off in different directions through the rock, widening and contracting their dimensions, and the roofs and floors are covered with stalactite. The bones are often broken, but do not seem to be water-worn. In some places they lie imbedded in loose earth, but they are usually included in a breccia.

The remains belong to marsupial animals. Among the most abundant are those of the kangaroo, of which there are four species, while others belong to the genera Phascolomys, the wombat; Dasyurus, the ursine opossum; Phalangista, the vulpine opossum; and Hypsiprymnus, the kangaroo-rat.

(FIGURE 91. Part of lower jaw of Macropus atlas. Owen. A young individual of an extinct species. a. Permanent false molar, in the alveolus.)

(FIGURE 92. Lower jaw of largest living species of kangaroo. (Macropus major.))

In the fossils above enumerated, several species are larger than the largest living ones of the same genera now known in Australia. Figure 91 of the right side of a lower jaw of a kangaroo (Macropus atlas, Owen) will at once be seen to exceed in magnitude the corresponding part of the largest living kangaroo, which is represented in Figure 92. In both these specimens part of the substance of the jaw has been broken open, so as to show the permanent false molar (a, Figure 91), concealed in the socket. From the fact of this molar not having been cut, we learn that the individual was young, and had not shed its first teeth.

The reader will observe that all these extinct quadrupeds of Australia belong to the marsupial family, or, in other words, that they are referable to the same peculiar type of organisation which now distinguishes the Australian mammalia from those of other parts of the globe. This fact is one of many pointing to a general law deducible from the fossil vertebrate and invertebrate animals of times immediately antecedent to our own, namely, that the present geographical distribution of organic FORMS dates back to a period anterior to the origin of existing SPECIES; in other words, the limitation of particular genera or families of quadrupeds, mollusca, etc., to certain existing provinces of land and sea, began before the larger part of the species now contemporary with man had been introduced into the earth.

Professor Owen, in his excellent "History of British Fossil Mammals," has called attention to this law, remarking that the fossil quadrupeds of Europe and Asia differ from those of Australia or South America. We do not find, for example, in the Europaeo-Asiatic province fossil kangaroos, or armadillos, but the elephant, rhinoceros, horse, bear, hyaena, beaver, hare, mole, and others, which still characterise the same continent.

In like manner, in the Pampas of South America the skeletons of Megatherium, Megalonyx, Glyptodon, Mylodon, Toxodon, Macrauchenia, and other extinct forms, are analogous to the living sloth, armadillo, cavy, capybara, and llama. The fossil quadrumana, also associated with some of these forms in the Brazilian caves, belong to the Platyrrhine family of monkeys, now peculiar to South America. That the extinct fauna of Buenos Ayres and Brazil was very modern has been shown by its relation to deposits of marine shells, agreeing with those now inhabiting the Atlantic.

The law of geographical relationship above alluded to, between the living vertebrata of every great zoological province and the fossils of the period immediately antecedent, even where the fossil species are extinct, is by no means confined to the mammalia. New Zealand, when first examined by Europeans, was found to contain no indigenous land quadrupeds, no kangaroos, or opossums, like Australia; but a wingless bird abounded there, the smallest living representative of the ostrich family, called the Kiwi by the natives (Apteryx). In the fossils of the Post-pliocene period in this same island, there is the like absence of kangaroos, opossums, wombats, and the rest; but in their place a prodigious number of well-preserved specimens of gigantic birds of the struthious order, called by Owen Dinornis and Palapteryx, which are entombed in superficial deposits. These genera comprehended many species, some of which were four, some seven, others nine, and others eleven feet in height! It seems doubtful whether any contemporary mammalia shared the land with this population of gigantic feathered bipeds.

Mr. Darwin, when describing the recent and fossil mammalia of South America, has dwelt much on the wonderful relationship of the extinct to the living types in that part of the world, inferring from such geographical phenomena that the existing species are all related to the extinct ones which preceded them by a bond of common descent.

CLIMATE OF THE POST-PLIOCENE PERIOD.

The evidence as to the climate of Europe during this epoch is somewhat conflicting. The fluviatile and land-shells are all of existing species, but their geographical range has not always been the same as at present. Some, for example, which then lived in Britain are now only found in Norway and Finland, probably implying that the Post-pliocene climate of Britain was colder, especially in the winter. So also the reindeer and the musk-ox (Ovibos moschatus), now inhabitants of the Arctic regions, occur fossil in the valleys of the Thames and Avon, and also in France and Germany, accompanied in most places by the mammoth and the woolly rhinoceros. At Grays in Essex, on the other hand, another species both of elephant and rhinoceros occurs, together with a hippopotamus and the Cyrena fluminalis, a shell now extinct in Europe but still an inhabitant of the Nile and some Asiatic rivers. With it occurs the Unio littoralis, now living in the Seine and Loire. In the valley of the Somme flint tools have been found associated with Hippopotamus major and Cyrena fluminalis in the lower-level Post-pliocene gravels; while in the higher-level (and more ancient) gravels similar tools are more abundant, and are associated with the bones of the mammoth and other Post-pliocene quadrupeds indicative of a colder climate.

It is possible that we may here have evidence of summer and winter migrations rather than of a general change of temperature. Instead of imagining that the hippopotamus lived all the year round with the musk-ox and lemming, we may rather suppose that the apparently conflicting evidence may be due to the place of our observations being near the boundary line of a northern and southern fauna, either of which may have advanced or receded during comparatively slight and temporary fluctuations of climate. There may then have been a continuous land communication between England and the North of Siberia, as well as in an opposite direction with Africa, then united to Southern Europe.

In drift at Fisherton, near Salisbury, thirty feet above the river Wiley, the Greenland lemming and a new species of the Arctic genus Spermophilus have been found, along with the mammoth, reindeer, cave-hyaena, and other mammalia suited to a cold climate. A flint implement was taken out from beneath the bones of the mammoth. In a higher and older deposit in the vicinity, flint tools like those of Amiens have been discovered. Nearly all the known Post-pliocene quadrupeds have now been found accompanying flint knives or hatchets in such a way as to imply their coexistence with man; and we have thus the concurrent testimony of several classes of geological facts to the vast antiquity of the human race. In the first place, the disappearance of a great variety of species of wild animals from every part of a wide continent must have required a vast period for its accomplishment; yet this took place while man existed upon the earth, and was completed before that early period when the Danish shell-mounds were formed or the oldest of the Swiss lake-dwellings constructed. Secondly, the deepening and widening of valleys, indicated by the position of the river gravels at various heights, implies an amount of change of which that which has occurred during the historical period forms a scarcely perceptible part. Thirdly, the change in the course of rivers which once flowed through caves now removed from any line of drainage, and the formation of solid floors of stalagmite, must have required a great lapse of time. Lastly, ages must have been required to change the climate of wide regions to such an extent as completely to alter the geographical distribution of many mammalia as well as land and fresh-water shells. The 3000 or 4000 years of the historical period does not furnish us with any appreciable measure for calculating the number of centuries which would suffice for such a series of changes, which are by no means of a local character, but have operated over a considerable part of Europe.

RELATIVE LONGEVITY OF SPECIES IN THE MAMMALIA AND TESTACEA.

I called attention in 1830 to the fact, which had not at that time attracted notice, that the association in the Post-pliocene deposits of shells, exclusively of living species, with many extinct quadrupeds betokened a longevity of species in the testacea far exceeding that in the mammalia. (Principles of Geology 1st edition volume 3 page 140.) Subsequent researches seem to show that this greater duration of the same specific forms in the class mollusca is dependent on a still more general law, namely, that the lower the grade of animals, or the greater the simplicity of their structure, the more persistent are they in general in their specific characters throughout vast periods of time. Not only have the invertebrata, as shown by geological data, altered at a less rapid rate than the vertebrata, but if we take one of the classes of the former, as for example the mollusca, we find those of more simple structure to have varied at a slower rate than those of a higher and more complex organisation; the Brachiopoda, for example, more slowly than the lamellibranchiate bivalves, while the latter have been more persistent than the univalves, whether gasteropoda or cephalopoda. In like manner the specific identity of the characters of the foraminifera, which are among the lowest types of the invertebrata, has outlasted that of the mollusca in an equally decided manner.

TEETH OF POST-PLIOCENE MAMMALIA.

To those who have never studied comparative anatomy, it may seem scarcely credible that a single bone taken from any part of the skeleton may enable a skilful osteologist to distinguish, in many cases, the genus, and sometimes the species, of quadrupeds to which it belonged. Although few geologists can aspire to such knowledge, which must be the result of long practice and study, they will nevertheless derive great advantage from learning, what is comparatively an easy task, to distinguish the principal divisions of the mammalia by the forms and characters of their teeth.

Figures 93 through 105 represent the teeth of some of the more common species and genera found in alluvial and cavern deposits.

(FIGURE 93. Elephas primigenius (or Mammoth ); molar of upper jaw, right side; one-third of natural size. Post-pliocene. a. Grinding surface. b. Side view.)

(FIGURE 94. Elephas antiquus, Falconer. Penultimate molar, one-third of natural size. Post-pliocene and Pliocene.)

(FIGURE 95. Elephas meridionalis, Nesti. Penultimate molar, one-third of natural size. Post-pliocene and Pliocene.)

(FIGURE 96. Rhinoceros leptorhinus, Cuvier— Rhin. megarhinus, Christol; fossil from fresh-water beds of Grays, Essex; penultimate molar, lower jaw, left side; two-thirds of natural size. Post-pliocene and Newer Pliocene.)

(FIGURE 97. Rhinoceros tichorhinus; penultimate molar, lower jaw, left side; two-thirds of natural size. Post-pliocene.)

(FIGURE 98. Hippopotamus; from cave near Palermo; molar tooth; two-thirds of natural size. Post-pliocene.)

(FIGURE 99. Horse. Equus caballus, L. (common horse); from the shell-marl, Forfarshire; second molar, lower jaw. Recent. a. Grinding surface, two-thirds natural size. b. Side view of same, half natural size.)

(FIGURE 100. Deer. Moose (Cervus alces, L.); recent; molar of upper jaw. a. Grinding surface. b. Side view, two-thirds of natural size.)

(FIGURE 101. Ox. Ox, common, from shell-marl, Forfarshire; true molar, upper jaw; two-thirds natural size. Recent. c. Grinding surface. d. Side view, fangs uppermost.)

(FIGURE 102. Bear. a. Canine tooth or tusk of bear (Ursus spelaeus); from cave near Liege. b. Molar of left side, upper jaw; one-third of natural size. Post-pliocene.)

(FIGURE 103. Tiger. c. Canine tooth of tiger (Felis tigris); recent. d. Outside view of posterior molar, lower jaw: one-third of natural size. Recent.)

(FIGURE 104. Hyaena spelaea, Goldf. (variety of H. crocuta); lower jaw. Kent's Hole, Torquay, Devonshire; one-third natural size. Post-pliocene.)

(FIGURE 105. Teeth of a new species of Arvicola, field-mouse; from the Norwich Crag. Newer Pliocene. a. Grinding surface. b. Side view of the same. c. Natural size of a and b.)

On comparing the grinding surfaces of the corresponding molars of the three species of elephants, Figures 93, 94, 95 it will be seen that the folds of enamel are most numerous in the mammoth, fewer and wider, or more open, in E. antiquus; and most open and fewest in E. meridionalis. It will be also seen that the enamel in the molar of the Rhinoceros tichorhinus (Figure 97), is much thicker than in that of the Rhinoceros leptorhinus (Figure 96).

CHAPTER XI.

POST-PLIOCENE PERIOD, CONTINUED.— GLACIAL CONDITIONS. (As to the former excess of cold, whether brought about by modifications in the height and distribution of the land or by altered astronomical conditions, see Principles volume 1 10th edition 1867 chapters 12 and 13 "Vicissitudes of Climate.")

Geographical Distribution, Form, and Characters of Glacial Drift. Fundamental Rocks, polished, grooved, and scratched. Abrading and striating Action of Glaciers. Moraines, Erratic Blocks, and "Roches Moutonnees." Alpine Blocks on the Jura. Continental Ice of Greenland. Ancient Centres of the Dispersion of Erratics. Transportation of Drift by floating Icebergs. Bed of the Sea furrowed and polished by the running aground of floating Ice- islands.

CHARACTER AND DISTRIBUTION OF GLACIAL DRIFT.

In speaking of the loose transported matter commonly found on the surface of the land in all parts of the globe, I alluded to the exceptional character of what has been called the boulder formation in the temperate and Arctic latitudes of the northern hemisphere. The peculiarity of its form in Europe north of the 50th, and in North America north of the 40th parallel of latitude, is now universally attributed to the action of ice, and the difference of opinion respecting it is now chiefly restricted to the question whether land-ice or floating icebergs have played the chief part in its distribution. It is wanting in the warmer and equatorial regions, and reappears when we examine the lands which lie south of the 40th and 50th parallels in the southern hemisphere, as, for example, in Patagonia, Tierra del Fuego, and New Zealand. It consists of sand and clay, sometimes stratified, but often wholly devoid of stratification for a depth of 50, 100, or even a greater number of feet. To this unstratified form of the deposit the name of TILL has long been applied in Scotland. It generally contains a mixture of angular and rounded fragments of rock, some of large size, having occasionally one or more of their sides flattened and smoothed, or even highly polished. The smoothed surfaces usually exhibit many scratches parallel to each other, one set of which often crosses an older set. The till is almost everywhere wholly devoid of organic remains, except those washed into it from older formations, though in some places it contains marine shells, usually of northern or Arctic species, and frequently in a fragmentary state. The bulk of the till has usually been derived from the grinding down into mud of rocks in the immediate neighbourhood, so that it is red in a region of Red Sandstone, as in Strathmore in Forfarshire; grey or black in a district of coal and bituminous shale, as around Edinburgh; and white in a chalk country, as in parts of Norfolk and Denmark. The stony fragments dispersed irregularly through the till usually belong, especially in mountainous countries, to rocks found in some part of the same hydrographical basin; but there are regions where the whole of the boulder clay has come from a distance, and huge blocks, or "erratics," as they have been called, many feet in diameter, have not unfrequently travelled hundreds of miles from their point of departure, or from the parent rocks from which they have evidently been detached. These are commonly angular, and have often one or more of their sides polished and furrowed.

The rock on which the boulder formation reposes, if it consists of granite, gneiss, marble, or other hard stone, capable of permanently retaining any superficial markings which may have been imprinted upon it, is usually smoothed or polished, like the erratics above described, and exhibits parallel striae and furrows having a determinate direction. This direction, both in Europe and North America, agrees generally in a marked manner with the course taken by the erratic blocks in the same district. The boulder clay, when it was first studied, seemed in many of its characters so singular and anomalous, that geologists despaired of ever being able to interpret the phenomena by reference to causes now in action. In those exceptional cases where marine shells of the same date as the boulder clay were found, nearly all of them were recognised as living species— a fact conspiring with the superficial position of the drift to indicate a comparatively modern origin.

The term "diluvium" was for a time the most popular name of the boulder formation, because it was referred by many to the deluge of Noah, while others retained the name as expressive of their opinion that a series of diluvial waves raised by hurricanes and storms, or by earthquakes, or by the sudden upheaval of land from the bed of the sea, had swept over the continents, carrying with them vast masses of mud and heavy stones, and forcing these stones over rocky surfaces so as to polish and imprint upon them long furrows and striae. But geologists were not long in seeing that the boulder formation was characteristic of high latitudes, and that on the whole the size and number of erratic blocks increases as we travel towards the Arctic regions. They could not fail to be struck with the contrast which the countries bordering the Baltic presented when compared with those surrounding the Mediterranean. The multitude of travelled blocks and striated rocks in the one region, and the absence of such appearances in the other, were too obvious to be overlooked. Even the great development of the boulder formation, with large erratics so far south as the Alps, offered an exception to the general rule favourable to the hypothesis that there was some intimate connection between it and accumulations of snow and ice.

TRANSPORTING AND ABRADING POWER OF GLACIERS.

(FIGURE 106. Limestone, polished, furrowed, and scratched by the glacier of Rosenlau in Switzerland. (Agassiz.) a a. White streaks or scratches, caused by small grains of flint frozen into the ice. b b. Furrows.)

I have described elsewhere ("Principles" volume 1 chapter 16 1867) the manner in which the snow of the Alpine heights is prevented from accumulating indefinitely in thickness by the constant descent of a large portion of it by gravitation. Becoming converted into ice it forms what are termed glaciers, which glide down the principal valleys. On their surface are seen mounds of rubbish or large heaps of sand and mud, with angular fragments of rock which fall from the steep slopes or precipices bounding the glaciers. When a glacier, thus laden, descends so far as to reach a region about 3500 feet above the level of the sea, the warmth of the air is such that it melts rapidly in summer, and all the mud, sand, and pieces of rock are slowly deposited at its lower end, forming a confused heap of unstratified rubbish called a MORAINE, and resembling the TILL before described.

Besides the blocks thus carried down on the top of the glacier, many fall through fissures in the ice to the bottom, where some of them become firmly frozen into the mass, and are pushed along the base of the glacier, abrading, polishing, and grooving the rocky floor below, as a diamond cuts glass, or as emery-powder polishes steel. The striae which are made, and the deep grooves which are scooped out by this action, are rectilinear and parallel to an extent never seen in those produced on loose stones or rocks, where shingle is hurried along by a torrent, or by the waves on a sea-beach. In addition to these polished, striated, and grooved surfaces of rock, another mark of the former action of a glacier is the "roche moutonnee." Projecting eminences of rock so called have been smoothed and worn into the shape of flattened domes by the glacier as it passed over them. They have been traced in the Alps to great heights above the present glaciers, and to great horizontal distances beyond them.

ALPINE BLOCKS ON THE JURA.

The moraines, erratics, polished surfaces, domes, and striae, above described, are observed in the great valley of Switzerland, fifty miles broad; and almost everywhere on the Jura, a chain which lies to the north of this valley. The average height of the Jura is about one-third that of the Alps, and it is now entirely destitute of glaciers; yet it presents almost everywhere similar moraines, and the same polished and grooved surfaces. The erratics, moreover, which cover it, present a phenomenon which has astonished and perplexed the geologist for more than half a century. No conclusion can be more incontestable than that these angular blocks of granite, gneiss, and other crystalline formations came from the Alps, and that they have been brought for a distance of fifty miles and upward across one of the widest and deepest valleys in the world; so that they are now lodged on a chain composed of limestone and other formations, altogether distinct from those of the Alps. Their great size and angularity, after a journey of so many leagues, has justly excited wonder; for hundreds of them are as large as cottages; and one in particular, composed of gneiss, celebrated under the name of Pierre a Bot, rests on the side of a hill about 900 feet above the lake of Neufchatel, and is no less than 40 feet in diameter.

In the year 1821, M. Venetz first announced his opinion that the Alpine glaciers must formerly have extended far beyond their present limits, and the proofs appealed to by him in confirmation of this doctrine were acknowledged by all subsequent observers, and greatly strengthened by new observations and arguments. M. Charpentier supposed that when the glaciers extended continuously from the Alps to the Jura, the former mountains were 2000 or 3000 feet higher than at present. Other writers, on the contrary, conjectured that the whole country had been submerged, and the moraines and erratic blocks transported on floating icebergs; but a careful study of the distribution of the travelled masses, and the total absence of marine shells from the old glacial drift of Switzerland, have entirely disproved this last hypothesis. In addition to the many evidences of the action of ice in the northern parts of Europe which we have already mentioned, there occur here and there in some of these countries, what are wanting in Switzerland, deposits of marine fossil shells, which exhibit so arctic a character that they must have led the geologist to infer the former prevalence of a much colder climate, even had he not encountered so many accompanying signs of ice-action. The same marine shells demonstrate the submergence of large areas in Scandinavia and the British Isles, during the glacial cold.

A characteristic feature of the deposits under consideration in all these countries is the occurrence of large erratic blocks, and sometimes of moraine matter, in situations remote from lofty mountains, and separated from the nearest points where the parent rocks appear at the surface by great intervening valleys, or arms of the sea. We also often observe striae and furrows, as in Norway, Sweden, and Scotland, which deviate from the direction which they ought to follow if they had been connected with the present line of drainage, and they, therefore, imply the prevalence of a very distinct condition of things at the time when the cold was most intense. The actual state of North Greenland seems to afford the best explanation of such abnormal glacial markings.

GREENLAND CONTINENTAL ICE.

Greenland is a vast unexplored continent, buried under one continuous and colossal mass of ice that is always moving seaward, a very small part of it in an easterly direction, and all the rest westward, or towards Baffin's Bay. All the minor ridges and valleys are levelled and concealed under a general covering of snow, but here and there some steep mountains protrude abruptly from the icy slope, and a few superficial lines of stones or moraines are visible at certain seasons, when no snow has fallen for many months, and when evaporation, promoted by the wind and sun, has caused much of the upper snow to disappear. The height of this continent is unknown, but it must be very great, as the most elevated lands of the outskirts, which are described as comparatively low, attain altitudes of 4000 to 6000 feet. The icy slope gradually lowers itself towards the outskirts, and then terminates abruptly in a mass about 2000 feet in thickness, the great discharge of ice taking place through certain large friths, which, at their upper ends, are usually about four miles across. Down these friths the ice is protruded in huge masses, several miles wide, which continue their course— grating along the rocky bottom like ordinary glaciers long after they have reached the salt water. When at last they arrive at parts of Baffin's Bay deep enough to buoy up icebergs from 1000 to 1500 feet in vertical thickness, broken masses of them float off, carrying with them on their surface not only fine mud and sand but large stones. These fragments of rock are often polished and scored on one or more sides, and as the ice melts, they drop down to the bottom of the sea, where large quantities of mud are deposited, and this muddy bottom is inhabited by many mollusca.

Although the direction of the ice-streams in Greenland may coincide in the main with that which separate glaciers would take if there were no more ice than there is now in the Swiss Alps, yet the striation of the surface of the rocks on an ice-clad continent would, on the whole, vary considerably in its minor details from that which would be imprinted on rocks constituting a region of separate glaciers. For where there is a universal covering of ice there will be a general outward movement from the higher and more central regions towards the circumference and lower country, and this movement will be, to a certain extent, independent of the minor inequalities of hill and valley, when these are all reduced to one level by the snow. The moving ice may sometimes cross even at right angles deep narrow ravines, or the crests of buried ridges, on which last it may afterwards seem strange to detect glacial striae and polishing after the liquefaction of the snow and ice has taken place.

Rink mentions that in North Greenland powerful springs of clayey water escape in winter from under the ice, where it descends to "the outskirts," and where, as already stated, it is often 2000 feet thick— a fact showing how much grinding action is going on upon the surface of the subjacent rocks. I also learn from Dr. Torell that there are large areas in the outskirts, now no longer covered with permanent snow or glaciers, which exhibit on their surface unmistakable signs of ancient ice-action, so that, vast as is the power now exerted by ice in Greenland, it must once have operated on a still grander scale. The land, though now very elevated, may perhaps have been formerly much higher. It is well-known that the south coast of Greenland, from latitude 60 degrees to about 70 degrees north, has for the last four centuries been sinking at the rate of several feet in a century. By this means a surface of rock, well scored and polished by ice, is now slowly subsiding beneath the sea, and is becoming strewed over, as the icebergs melt, with impalpable mud and smoothed and scratched stones. It is not precisely known how far north this downward movement extends.