It is fortunate that the channels do not coincide, for this enables us to distinguish the more ancient deposits. A glance at a geological map shows, however, that they must coincide elsewhere, and where the Thames has re-occupied its old channel it is clear that the destruction of the earlier deposits may have led to a mixture of fossils and implements belonging to three different dates. Mammoth teeth and Palaeolithic implements, Irish elk and polished stone implements, may all be dredged up in the modern river gravel, associated with bits of iron chain, old shoes, and pottery. Such a mixture does actually occur in the Thames estuary, and it makes us hesitate to accept the teeth of mammoth which were dredged in the Thames as really belonging to so late a period as that of the submerged forests. At Clacton a similar difficulty is met with, for there again an ancient channel contains alternating estuarine and freshwater deposits with layers of peat, and is full of bones belonging to rhinoceros, hippopotamus, elephant and other extinct mammalia. Of course the peat-beds in this channel are just as much entitled to the name “submerged forest” as the more modern deposits to which recent usage restricts it. They belong, however, to another and more ancient chapter of the geological record than that with which we are now dealing. I do not say a less interesting one, for they are of the greatest importance when we study the times when Palaeolithic man flourished; but at present we have as much as we can do to understand the later deposits and to realize the great changes to which they point. We must not turn aside for everything of interest that we come across in this study; these earlier strata are worthy of a book to themselves. As we travel northward along the coast, again and again we meet with evidence of a submerged nearly level platform, “basal plane,” or ancient “plane of marine denudation,” lying about 50 feet below the sea. We find it at Langer Fort, which lies opposite to Harwich on a spit of sand and shingle stretching across Harwich Harbour. Here the floor of London Clay was met with in a boring at 54 feet below the surface. The Suffolk coast north of Southwold yields yet another complication, for between Southwold and Sherringham in Norfolk there appears at the sea-level a land-surface considerably more ancient than anything we have yet been dealing with. This is the so-called “Cromer Forest-bed,” which consists of alternating freshwater and estuarine beds, with ancient land-surfaces and masses of peat. It contains numerous extinct mammals, mainly of species older than and different from those of Clacton and Grays.