Sept.12th.--During the last six days, the worms have not been active, though many castings have been ejected in the neighbouring fields; but on this day the earth was a little raised over the mouths of the burrows, or castings were ejected, at ten fresh points.These were defaced.It should be understood that when a fresh burrow is spoken of, this generally means only that an old burrow has been re-opened.Mr.Farrer was repeatedly struck with the pertinacity with which the worms re-opened their old burrows, even when no earth was ejected from them.I have often observed the same fact, and generally the mouths of the burrows areprotected by an accumulation of pebbles, sticks or leaves.Mr.Farrer likewise observed that the worms living beneath the floor of the atrium often collected coarse grains of sand, and such little stones as they could find, round the mouths of their burrows.
Sept.13th; soft wet weather.The mouths of the burrows were re- opened, or castings were ejected, at 31 points; these were all defaced.
Sept.14th; 34 fresh holes or castings; all defaced.Sept.15th; 44 fresh holes, only 5 castings; all defaced.Sept.18th; 43 fresh holes, 8 castings; all defaced.
The number of castings on the surrounding fields was now very large.Sept.19th; 40 holes, 8 castings; all defaced.
Sept.22nd; 43 holes, only a few fresh castings; all defaced.Sept.23rd; 44 holes, 8 castings.
Sept.25th; 50 holes, no record of the number of castings.Oct.13th; 61 holes, no record of the number of castings.
After an interval of three years, Mr.Farrer, at my request, again looked at the concrete floor, and found the worms still at work.
Knowing what great muscular power worms possess, and seeing how soft the concrete was in many parts, I was not surprised at its having been penetrated by their burrows; but it is a more surprising fact that the mortar between the rough stones of the thick walls, surrounding the rooms, was found by Mr.Farrer to have been penetrated by worms.On August 26th, that is, five days after the ruins had been exposed, he observed four open burrows on the broken summit of the eastern wall (W in Fig.8); and, on September 15th, other burrows similarly situated were seen.It should also be noted that in the perpendicular side of the trench (which was much deeper than is represented in Fig.8) three recent burrows were seen, which ran obliquely far down beneath the base of the old wall.
We thus see that many worms lived beneath the floor and the walls of the atrium at the time when the excavations were made; and that they afterwards almost daily brought up earth to the surface from a considerable depth.There is not the slightest reason to doubt that worms have acted in this manner ever since the period when the concrete was sufficiently decayed to allow them to penetrate it; and even before thatperiod they would have lived beneath the floor, as soon as it became pervious to rain, so that the soil beneath was kept damp.The floor and the walls must therefore have been continually undermined; and fine earth must have been heaped on them during many centuries, perhaps for a thousand years.If the burrows beneath the floor and walls, which it is probable were formerly as numerous as they now are, had not collapsed in the course of time in the manner formerly explained, the underlying earth would have been riddled with passages like a sponge; and as this was not the case, we may feel sure that they have collapsed.The inevitable result of such collapsing during successive centuries, will have been the slow subsidence of the floor and of the walls, and their burial beneath the accumulated worm-castings.The subsidence of a floor, whilst it still remains nearly horizontal, may at first appear improbable; but the case presents no more real difficulty than that of loose objects strewed on the surface of a field, which, as we have seen, become buried several inches beneath the surface in the course of a few years, though still forming a horizontal layer parallel to the surface.The burial of the paved and level path on my lawn, which took place under my own observation, is an analogous case.Even those parts of the concrete floor which the worms could not penetrate would almost certainly have been undermined, and would have sunk, like the great stones at Leith Hill Place and Stonehenge, for the soil would have been damp beneath them.But the rate of sinking of the different parts would not have been quite equal, and the floor was not quite level.The foundations of the boundary walls lie, as shown in the section, at a very small depth beneath the surface; they would therefore have tended to subside at nearly the same rate as the floor.But this would not have occurred if the foundations had been deep, as in the case of some other Roman ruins presently to be described.
Finally, we may infer that a large part of the fine vegetable mould, which covered the floor and the broken-down walls of this villa, in some places to a thickness of 16 inches, was brought up from below by worms.From facts hereafter to be given there can be no doubt that some of the finest earth thus brought up will have been washed down the sloping surface of the field during every heavy shower of rain.If this had notoccurred a greater amount of mould would have accumulated over the ruins than that now present.But beside the castings of worms and some earth brought up by insects, and some accumulation of dust, much fine earth will have been washed over the ruins from the upper parts of the field, since it has been under cultivation; and from over the ruins to the lower parts of the slope; the present thickness of the mould being the resultant of these several agencies.