A second wall was exposed to view for the first time, and an open burrow was seen on its broken summit.By separating the flints this burrow was traced far down in the interior of the wall; but as some of the flints cohered firmly, the whole mass was disturbed in pulling down the wall, and the burrow could not be traced to the bottom.The foundations of a third wall, which appeared quite sound, lay at a depth of 4 feet beneathone of the floors, and of course at a considerably greater depth beneath the level of the ground.A large flint was wrenched out of the wall at about a foot from the base, and this required much force, as the mortar was sound; but behind the flint in the middle of the wall, the mortar was friable, and here there were worm-burrows.Mr.Joyce and my sons were surprised at the blackness of the mortar in this and in several other cases, and at the presence of mould in the interior of the walls.Some may have been placed there by the old builders instead of mortar; but we should remember that worms line their burrows with black humus.Moreover open spaces would almost certainly have been occasionally left between the large irregular flints; and these spaces, we may feel sure, would be filled up by the worms with their castings, as soon as they were able to penetrate the wall.Rain- water, oozing down the burrows would also carry fine dark-coloured particles into every crevice.Mr.Joyce was at first very sceptical about the amount of work which I attributed to worms; but he ends his notes with reference to the last-mentioned wall by saying, "This case caused me more surprise and brought more conviction to me than any other.I should have said, and did say, that it was quite impossible such a wall could have been penetrated by earth-worms."In almost all the rooms the pavement has sunk considerably, especially towards the middle; and this is shown in the three following sections.The measurements were made by stretching a string tightly and horizontally over the floor.The section, Fig.13, was taken from north to south across a room, 18 feet 4 inches in length, with a nearly perfect pavement, next to the "Red Wooden Hut." In the northern half, the subsidence amounted to5.75 inches beneath the level of the floor as it now stands close to the walls; and it was greater in the northern than in the southern half; but, according to Mr.Joyce, the entire pavement has obviously subsided.In several places, the tesserae appeared as if drawn a little away from the walls; whilst in other places they were still in close contact with them.
In Fig.14, we see a section across the paved floor of the southern corridor or ambulatory of a quadrangle, in an excavation made near "The Spring." The floor is 7 feet 9 inches wide, and the broken- down walls now project only 0.75 of an inch above its level.The field, which was inpasture, here sloped from north to south, at an angle of 30 degrees, 40 seconds.The nature of the ground at some little distance on each side of the corridor is shown in the section.It consisted of earth full of stones and other debris, capped with dark vegetable mould which was thicker on the lower or southern than on the northern side.The pavement was nearly level along lines parallel to the side-walls, but had sunk in the middle as much as 7.75 inches.
A small room at no great distance from that represented in Fig.13, had been enlarged by the Roman occupier on the southern side, by an addition of 5 feet 4 inches in breadth.For this purpose the southern wall of the house had been pulled down, but the foundations of the old wall had been left buried at a little depth beneath the pavement of the enlarged room.Mr.Joyce believes that this buried wall must have been built before the reign of Claudius II., who died 270 A.D.We see in the accompanying section, Fig.15, that the tesselated pavement has subsided to a less degree over the buried wall than elsewhere; so that a slight convexity or protuberance here stretched in a straight line across the room.This led to a hole being dug, and the buried wall was thus discovered.
We see in these three sections, and in several others not given, that the old pavements have sunk or sagged considerably.Mr.Joyce formerly attributed this sinking solely to the slow settling of the ground.That there has been some settling is highly probable, and it may be seen in Fig.15 that the pavement for a width of 5 feet over the southern enlargement of the room, which must have been built on fresh ground, has sunk a little more than on the old northern side.But this sinking may possibly have had no connection with the enlargement of the room; for in Fig.13 one half of the pavement has subsided more than the other half without any assignable cause.In a bricked passage to Mr.Joyce's own house, laid down only about six years ago, the same kind of sinking has occurred as in the ancient buildings.Nevertheless it does not appear probable that the whole amount of sinking can be thus accounted for.The Roman builders excavated the ground to an unusual depth for the foundations of their walls, which were thick and solid; it is therefore hardly credible that they should have been careless about the solidity of the bed on which their tesselatedand often ornamented pavements were laid.The sinking must, as it appears to me, be attributed in chief part to the pavement having been undermined by worms, which we know are still at work.Even Mr.Joyce at last admitted that this could not have failed to have produced a considerable effect.Thus also the large quantity of fine mould overlying the pavements can be accounted for, the presence of which would otherwise be inexplicable.My sons noticed that in one room in which the pavement had sagged very little, there was an unusually small amount of overlying mould.