Then comes a stratum of dark silt, about 12 inches thick, with decomposed vegetable matter, and on this a layer of leaves of trees, hazel nuts, sticks and moss for 6 or 12 inches more. This layer of vegetable matter is about 30 feet below the level of the sea at low-water and about 48 feet at spring tides. It extends with some interruption across the valley. The point is not made quite clear in Colenso’s account, but apparently there is no marine deposit between the “tin ground” and the peat, the oyster-bed above mentioned representing the base of bed _c_, which at that point has cut through the peat, so as to lay bare part of the gravel and some of the oak-stumps rooted in it. So far, wherever we have a carefully noted section of the lowest deposits in these valleys, the tin ground or the gravels are directly succeeded by a growth of oak trees. It looks as though the climate ameliorated, the more violent floods ceased, and an oak forest grew across the alluvial flats, without there being any, or much, change of sea-level. (_c_) Above the vegetable matter and leaves (_b_) was found a “stratum of sludge or silt” 10 feet in thickness. It showed little variation except from a brownish to a lead colour. “The whole is sprinkled with recent shells, together with wood, hazel nuts, and sometimes the bones and horns of deer, oxen, etc. The shells, particularly the flat ones, are frequently found in rows or layers; they are often double or closed, with their opening part upwards.” From Colenso’s account it seems probable that this bed was a marine silt with _Scrobicularia_ and cockles in the position of life. He goes on to say that “There has been recently found imbedded in the silt, about two feet from the top, a piece of oak, that had been brought into form by the hand of man; it is about six feet long, one inch and a half broad, and less than half an inch thick; this is the greatest depth at which I have ever seen any converted substance. It appears to have floated in the sea, as at one end, which is much decayed, a small barnacle has fixed its habitation.” (_d_) _A stratum of sea-sand_, about four inches in thickness; this is easily distinguished from the river-sand, being much finer, and having always more or less shells mixed with it. (_e_) _Silt_ two feet, with concretions containing wood and bones. (_f_) _Another stratum of sea-sand_, 20 feet in thickness. In all parts of this sand there are timber trees, chiefly oaks, lying in all directions; also remains of animals such as red deer, “heads of oxen of a different description from any now known in Britain, the horns of which all turn downwards.” Human skulls were also found near the bottom of the sand, and one of these with other fossils was presented by Colenso to the Royal Geological Society of Cornwall. In the upper part of this sand nearer the mouth of the harbour, the bones of a large whale were found. The sea at this time seems to have extended about a mile up the valley.