rhinoceri, all clad in fleeces as if to protect them from the rigours of an Arctic climate, are found making their home in the basin of the Thames, where the forests afforded them suitable food.* Here, as in adjacent parts of England, they shared the land with the reindeer and the bear. Here around London roamed The wild herds that own no master's stall. The lion, the tiger and other carnivora followed in the track of the vegetable-feeding animals. The victims sometimes of sudden floods, they were engulfed in the deep waters, and in time embedded in the mud of the stream. The remains of these huge pre-Adamites and fierce carnivora thus survived great changes in the physical condition of the country in which they lived, and reveal to man in after ages the zoology and geography of their period. A Visit to the Graves of the Thames Mammoths. We may easily see for ourselves what kind of chronicles they are which tell of the continental ages of our country's history, when Mighty pre-Adamites walked the earth Of which ours is the wreck when herds of mammoths and rhinoceri found a natural home in England and roamed at will from the banks of the Thames to the Seine. For this purpose let us make a visit to one of the graves of these old zoological races. We may choose the Erith sand-pits on the south shore of the river, or the Ilford and Gray's brick-fields on the north as the place of our visit. In either case we shall find that the river has been its own historian, and the historian of the surrounding country, under geographical circumstances greatly differing from those of to-day. The Ilford brick-fields should be preferred, as they are celebrated for their mammalian remains of the early Thames-country. The pit which has the greatest repute for containing bones of the mammoth and rhinoceros is about a quarter of a mile beyond Ilford, on the left hand side of the high road from London to Ipswich. A visit early in the year is the most likely to *See British Fossil Mammals: Prof. OWEN. reward us for our trouble. In the early spring the pits are open for the purpose of removing the clay for the uses of the brick-field. As the earth is removed and the perpendicular sections are gradually exposed, we may look hopefully for some indications of animal remains. The workmen at length call our attention to a spot where the earth is denser, richer in colour, and more unctuous than that which surrounds it. But unless some skilled fossil-seeker is attached to the party, the embedded mammoth or hippopotamus may even now vanish before our eyes. The bones must be uncovered with the greatest ingenuity and care, if they are to be properly extricated from their earthy matrix and preserved in a permanent form. These mortal remains are generally as friable as the soil itself, and the evaporation which sets in as soon as they are exposed to the air causes them in many instances rapidly to crumble away. But invention, in fossil-seeking as in other pursuits, is born of necessity, and we have seen at Ilford, as well as at other fossil localities, an ingenious method of extricating and preserving the imperilled and vanishing prize. With moist clay and plaster of Paris the upper side of the bone or skeleton is first coated. With skill, patience, and careful under-cutting, the prize is at length turned over, and its under-side similarly treated. After entire excavation the bones are immersed in liquid size, of which they are allowed to absorb sufficient to keep them from fracture and fit them for removal. The hardening process is completed by giving them a bath of hot sand, in which they remain for a day or two, By a treatment of which these are the chief processes, not a few valuable remains of the Thames pachyderms discovered at Ilford and Erith, which would otherwise have perished in extrication, or within a short time of exposure, have been preserved for the national museum or private collection.* These remains of gigantic and now extinct species of quadrupeds * A full description of this process is given in The Field, March 6, 1869, by J. H. L. Sir Antonio Brady, a great collector of the pre-historic remains of the Thames Valley, intends to deposit his magnificent series of mammoth and other fossil specimens in the new East London Museum.-Ibid. which once ranged from the basin of the Thames to the basin of the Somme, and which, perhaps, became the victims of the great river in times of devastating floods as they browsed on the plain, are found by the fossil-seeker of to-day in fluviatile deposits at such distances from the present stream as to afford us some indication of the great changes which have taken place in the geography of the Thames since they were first engulfed in its waters. They tell us of the higher level at which the old river ran, of the greater volume of waters that poured down the valley, and of changes in the site of the main channel. The bones of the mammoth, rhinoceros, and hippopotamus, are found to-day in old silted-up channels of the Thames, and among the deposits of loam and gravel that have long since been left high and dry above the level of the stream, miles away from its present bed. It is these wide-ranging deposits of the river, the gravel, sand, and brick-earth that underlie the rich pastures and fruitful gardens of the Thames valley, that supply us with the fuller memoirs of the geography of the mammoth-period in south-eastern Britain. The Thames gravel, upon which London is built, and the beds of sediment that are found associated with it, are especially useful to the geographer in restoring the hydrography of the old valley. "The gravel consists of broken and slightly worn chalk flints of an ochreous colour, extends from above Maidenhead, through the metropolis, to the sea. Its width varies from two to nine miles. Its thickness ranges commonly from five to fifteen feet." 66 'Interstratified with it in many places are beds of sand, loam, and clay. The united thickness of these beds amounts to forty and even to sixty feet. The whole contains occasional remains of the mammoth and other extinct quadrupeds. These beds tell us both of the zoology of the ancient Thames country, and are a natural plan of the terraqueous arrangements of the old Thames Valley. It is in the light of geographical and zoological memoirs such as * PRESTWICH, Quarterly Geological Journal, vol. xii. p. 131. Wood, jun, contends Mr. S. V. that the Thames gravel does not extend to the sea, but stops short at Shoeburyness.-Geological Magazine. these, that we come to look with the geologist upon the Thames as nothing less than a grand memorial of an earlier world. We see that in ages prior to human chronicles, when the Thames was its own and sole biographer, it left us in its channel the records of a landsurface and zoology which are at first with difficulty recognised as the antecedents of those of to-day. Since the days of the Thames mammoth rivers have shifted their courses, and old hydrographical systems have been merged into new. The broad valley, Where palaces, and fanes, and villas rise, conceals under its verdurous carpet the alluvium of the great river by which it was excavated; and the Thames of to-day, as we shall see hereafter, flows over the tops of the still-standing trees of a submerged forest. It was not then too much to say that if we turned for a time from the human aspects and associations of the Thames to the tale which the river tells of itself before it entered the annals of Britain, or became the servant of civilised man, we should not fail to be rewarded for the study. It may be that further chapters in the autobiography of the Thames will take us back to a yet earlier time than that of the mammoth-period of Britain. But enough has been said for the present to affirm the claim to our interest which the Thames possesses as a memorial of ancient Nature and an earlier world. And whenever hereafter we rest and muse in holiday mood on the gravelly heights of Richmond and Greenwich, surveying the great placid stream below us, we shall look with more intelligent eye and with greater reverence on a feature of the landscape which so embodies the natural history of our country from its primeval ages. CHAPTER II. THE THAMES-COUNTRY BEFORE THE MAMMOTH-PERIOD.-REVIEW OF THE MAMMOTH-PERIOD OF THE THAMES.-EARLIER ANNALS OF THE THAMES. -THE GLACIAL CLAY OF MUSWELL HILL AND THE ESSEX HEIGHTS. -SUBMARINE ENGLAND: THE GLACIAL PERIOD.-EMERGENCE OF THE LAND.-ENGLAND AS AN ARCHIPELAGO.-MAP OF THE EARLY THAMESCOUNTRY.-THE THAMES A MARINE VALLEY.-THE RISING LAND-SURFACE: INCIPIENT RIVERS AND BASINS.-THE THAMES BEGINS TO BE A FRESHWATER RIVER. HE period when the mammoth flourished in the Thames Valley is incalculably far removed from the earliest events in Britain which human historians have chronicled. Great is the gulf that lies between the geographical and zoological conditions of the England of to-day and those of the far different England of the time of the mammoth. Nothing should we know of that early era of terrestrial history around London had not the Thames itself recorded in its valley the physical events of the time. It is to the Thames itself that we owe the knowledge that the landscapes through which it flows were for ages the home of Siberian elephants and fleece-clad rhinoceri. In the brickpits by the side of the Thames of to-day we may see for ourselves the wonderful relics which give to the mammoth and his fellows a place in the natural history of England. The self-recorded annals of the Thames extend even farther back than the mammoth-period of the valley's history. The geologist reads them as a record extending to the beginnings of terrestrial life in the landscapes around London. They take him back to the time when the land was as yet but unclad with vegetation, and slowly appearing above the sea. But the Thames-country of the British elephant and rhinoceros was no desert island, void of food and |