Perhaps we may still find submerged stone-circles or other antiquities of the age of Stonehenge beneath the sea-level; but Stonehenge lies too high above the sea for it in itself to give any clue as to a change of sea-level. We will only make one suggestion. It is probable that when Stonehenge was built, a long arm of the sea extended far up the Avon Valley, so that navigable water was found not far from Stonehenge. There is in Stonehenge an inner circle of smaller stones, not composed of the local greywethers but consisting of large blocks of igneous rock of foreign origin. These blocks, which are sufficiently large to be awkward for land-carriage, have been said to be erratics gathered on Salisbury Plain, just as the greywethers for the main circle were gathered; but there are no erratics on Salisbury Plain. Large erratic blocks of similar character occur, however, abundantly on the lowlands of Selsey Bill, under the lee of the Isle of Wight. Probably a similar erratic-strewn plain once fringed the coast on the west also, though on the exposed side the part above the sea-level has now been entirely swept away by the sea. I would suggest that the Stonehenge erratics, instead of being brought from any great distance, may have come from a wide plain at the mouth of the Avon, then two or three miles further seaward. From thence they were rafted far up the navigable fjord, not yet silted up, and were only carried a short distance uphill. Igneous rocks such as these, found in a country consisting essentially of chalk and Tertiary strata, would be valuable and probably endowed with magic properties, hence their employment in this inner circle. Our next enquiry must be into the length of time represented by the series of submerged forests and associated deposits described in the foregoing pages. The newest of them belongs certainly to the age of polished stone, and the earliest also probably comes within the Neolithic Period. Within the period represented by the submerged forests, we have seen that there has been a change of the sea-level to the extent of 80 feet, or perhaps rather more. If we can obtain some measure of the time occupied, this should give us some approximate idea as to the length of the Neolithic period, and of the rate at which changes of the sea-level can take place.