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 A HISTORY OF NORTHAMPTONSHIRE The age of the extinct or now foreign mammaHa and contempo- raneous man is a matter of much interest and importance ; let us briefly review the evidence. The remains cannot be admitted to be of Pre- glacial or Lower Glacial age, nor of the age of the formation of the Mid- glacial Gravels for various reasons, but most conclusively because none of the deposits of these periods contain any trace of such remains. In like manner and for like reasons we can cut out the Second Glacial period, hence they must be of Mid-glacial or Post-glacial age. Now the river gravels, as gravels, are of course of post-glacial age, and merge almost imperceptibly into the slightly newer Alluvium, an excellent preservative of animal remains, but one which contains only a present-day fauna. The inference that man and the mammoth were contemporaries in the Inter- glacial period thus seems incontestible. Still we have to account for the occurrence of these animals only in the river valleys. The remains of animals do not last long unless quickly buried in non-porous material, or at least where air and water cannot frequently change places, and such conditions would only prevail inland in the alluvial flats of the river valleys. The wash-out of an interglacial alluvium from the basement layers of a valley glacier seems to offer the only adequate explanation of the kind, number, condition and position of the remains. River Alluvium The river gravel of the central portion of the Nene valley passes upwards into sandy clays or silts containing much organic matter. This is a deposit dropped by dirty waters coming from adjacent hills or more distant parts of the watershed, whereas the river gravel is a residue left by the removal of just such material from a mixed Drift and Alluvium of an earlier period ; hence, although so nearly of the same age as gravel and clay respectively, the difference of fauna proves a great break in time of each as a sediment. For these reasons we have kept the nomenclature of the two more distinct than is common. When the extra-ordinary floods of the declining Glacial age passed into ordinary ones, each left fine sedimentary matter behind to fill up all inequalities of surface, and convert the valley into a dead level — the Great Flood Plane — through which the river now takes its winding course to the sea. The Alluvium abounds in remains of vegetation and molluscs identical with those inhabiting the waters to-day ; human remains occur rarely, though a skull is reported to have been found at a considerable depth in it between Castle Station and Hunsbury Hill, Northampton. Near to the Nun Mills, at Northampton, a long bone of an ox (?) was found with a well-bored hole at each end, as though it had been used as a yoke for domestic cattle. At Mr. Martin's brickyard, near Spencer Bridge, Northampton, a bowl with handle cut out of one piece of wood was found, and here too, although the alluvium itself was thin, several large trees lay, apparently stranded in a bend of the old river, and ulti- mately buried by slips of clay from a higher level. The trees were probably all oak, but fruits of other plants were found. The following 30