GEOLOGY and silts are mostly marine or estuarine, and as Mr. Skertchly has pointed out, there is every gradation from the ' buttery clay ' (as it is called) to silt. The clays contain woody fragments with vivianite (phosphate of iron), and there is usually at the base a floor of sand and gravel with marine shells. The fossils contained in these deposits are the familiar estuarine forms, such as Scrobicularia plana [piperata), Tellina balthica, Cardium edule, Ostrea edulis and Mytilus edulis, many of them dwarfed. In addition we occasionally find bones of animals such as are found in the alluvium, and also remains of whale, grampus and seal. The peat contains trunks of trees, remains of ' buried forests,' which are usually found near the borders of the Fenland or around islands in the levels. The Fenland area was once an arm of the sea, the materials were mostly brought in by the sea, and the silting up has long been going on. Formerly a morass, with here and there extensive pools of water, the Fenland has been greatly modified by the works of man. Portions of it were embanked and drained by the Romans ; but after their departure the sea returned, and large tracts were covered with beds of marine silt. These areas have again been reclaimed and converted into productive lands. In some places a breadth of three miles has been gained since the Roman occupation. The scenery is naturally monotonous, but it has its own peculiar charms, although, with the exception of the willows and aspens which fringe the watercourses, there are few trees. The Lynn Deeps, in which are channels over five fathoms deep in the middle of the Wash, may have been scooped out of the clayey deposits by tidal action ; but in Mr. Jukes-Browne's opinion the scour of the tides may have operated on an ancient valley formed by the old Fen rivers. This subject may be studied with reference to the deep alluvial valleys in East Norfolk, previously mentioned. In these old times the Fen rivers may have joined the Rhine estuary, and the marshlands in north Norfolk may be remnants of the old alluvial valley in Pleistocene times. On the foreshore north-west of Old Hunstanton and Holm, and at low-water level between Hunstanton and Brancaster, there are traces of a ' submerged forest,' equivalent probably to one of the peaty layers and buried forests in the Fenland. Oak, elm, birch and yew, willow and sallow have been found in this peaty deposit, the roots being fixed in the bed underlying the peat. Some of the alluvial tracts near Wells, StifFkey and Morston, are known as salt marshes, as they are liable to be flooded at high tide, which is not the case at Brancaster, Burnham and Cley, where the marshes are protected by embankments. BLOWN SAND The marshes on the north coast of Norfolk, as well as those bordering the Hundred stream and the Bure, near Breydon Water, are 25
