The Formation of Vegetable Mould through the Action of Worms

a castle ; and it is certain that they have been removed. The position of the nave-transept was ascertained not long ago by the foundations having been found; and the place is now marked by stones let into the ground. Where the abbey formerly stood, there now extends a smooth erass- covered surface, which resembles in all respects the rest of the field. The guardian, a very old man, said the surface had never been levelled in his time. In the year 1853, the Duke of Buccleuch had three holes dug in the turf within a few yards of one another, at the western end of the nave; and the old tesselated pavement of the abbey was thus discovered. These holes were afterwards surrounded by brickwork, and protected by trap-doors, so that the pavement might be readily inspected and preserved. When my son William examined the place on January 5, 1872, he found that the pavement in the three holes lay at depths of 6%, 10 and 114 inches beneath the surrounding turf-covered surface. The old guardian asserted that he was often forced to remove worm-castings from the pavement; and that he had done

so about six months before. My son collected all from one of the holes, the area of which was 5°32 square feet, and they weighed 7:97 ounces. Assuming that this amount had accumulated in six months, the accumulation during a year on a square yard would be 1-68 pounds, which, though a large amount, is very small compared with what, as we have seen, is often ejected on fields and commons. When I visited the abbey on June 22, 1877, the old man said that he had cleared out the holes about a month before, but a good many castings had since been ejected. I suspect that he imagined that he swept the pavements oftener than he really did, for the conditions were in several re- spects very unfavourable for the accumulation of even a moderate amount of castings. The tiles are rather large, viz., about 5% inches square, and the mortar between them was in most places sound, so that the worms were able to bring up earth from below only at certain points. The tiles rested on a bed of zoncrete, and the castings in consequence con- sisted in large part (viz., in the proportion of 19 to 33) of particles of mortar, grains of

sand, little fragments of rock, bricks or tile ; and such substances could hardly be agreeable, and certainly not nutritious, to worms. My son dug holes in several places within the former walls of the abbey, at a distance of several yards from the above described bricked squares. He did not find any tiles, though these are known to occur in some other parts, but he came in one spot to con- crete on which tiles had once rested. The fine mould beneath the turf on the sides of the several holes, varied in thickness from only 2 to 23 inches, and this rested on a layer from 8% to above 11 inches in thickness, consisting of fragments of mertar and stone- rubbish with the interstices compactly filled up with black mould. In the surrounding field, at a distance of 20 yards from the abbey, the fine vegetable mould was 11 inches thick.

We may conclude from these facts that when the abbey was destroyed and the stones removed, a layer of rubbish was left over the whole surface, and that as soon as the worms were able to penetrate the decayed concrete and the joints between the tiles, they slowly filled up the interstices in the overlying rubbish with their castings, which were after- wards accumulated to a thickness of nearly three inches over the whole surface. If we add to this latter amount the mould between the fragments of stones, some five or six inches of mould must have been brought up from beneath the concrete or tiles. The con- crete or tiles will consequently have subsided to nearly this amount. The bases of the columns of the aisles are now buried beneath mould and turf. It is not probable that they can have been undermined by worms, for their foundations would no doubt have ~ been laid at a considerable depth. If they have not subsided, the stones of which the columns were constructed must have been removed from beneath the former level of the floor.

Chedworth, Gloucestershire-—The remains of a large Roman villa were discovered here in 1866, on ground which had been covered with wood from time immemorial. No suspicion seems ever to have been enter- tained that ancient buildings lay buried here, until a gamekeeper, in digging for rabbits, encountered some remains.* But subse- quently the tops of some stone walls were de- tected in parts of the wood, projecting a little above the surface of the ground. Most of the coins found here belonged to Constans (who died 350 a.p.) and the Constantine family. My sons Francis and Horace visited the place in November 1877, for the sake of ascertaining what part worms may have played in the burial of these extensive re- mains. But the circumstances were not favourable for this object, as the ruins are sur- rounded on three sides by rather steep banks, down which earth is washed during rainy weather. Moreover most of the old rooms have been covered with roofs, for the pro- tection of the elegant tesselated pavements. A few facts may, however, be given on the thickness of the soil over these ruins. Close outside the northern rooms there is a broken wall, the summit of which was covered by 5

“ Several accounts of these ruins have been published; the pest is by Mr. James Farrer in ‘Proc. Soc. of Antiquaries of Scotland,’ vol. vi, Part II., 1867, p. 278. Also J. W. Grover, ‘Journal of the British Arch. Assoc. June 1866. Professor Buckman has likewise published a pamphlet, ‘Notes on the Roman Villa at Chedworth,’ 2nd edit. 1873: Cirencester, inches of black mould; and in a hole dug on the outer side of this wall, where the ground had never before been disturbed, black mould, full of stones, 26 inches in thickness, was found, resting on the undisturbed sub-soil of yellow clay. Ata depth of 22 inches from the surface a pig’s jaw and a fragment of a tile were found. When the excavations were first made, some large trees grew over the ruins; and the stump of one has been left directly over a party-wall near the bath room, for the sake of showing the thickness of the superincumbent soil, which was here 38 inches. In one small room, which, after being cleared out, had not been roofed over, my sons observed the hole of a worm passing through the rotten concrete, and a_ living worm was found within the concrete. In another open room worm-castings were seen or the floor, over which some earth had by this means been deposited, and here grass now grew.

Brading, Isle of Wight—A. fine Roman villa was discovered here in 1880; and by the end of October no less than 18 chambers had been more or less cleared. A coin dated 337 A.D. was found. My son William visited the place before the excavations were com- pleted; and he informs me that most of the floors were at first covered with much rubbish and fallen stones, having their interstices completely filled up with mould, abounding as the workmen said, with worms, above which there was mould without any stones. The whole mass was in most places from 3 to above 4 ft. in thickness. In one very large room the overlying earth was only 2 ft. 6 in. thick; and after this had been re- moved, so many castings were thrown up between the tiles that the surface had to be almost daily swept. Most of the floors were fairly level. The tops of the broken- down walls were covered in some places by only 4 or 5 inches of soil, so that they were occasionally struck by the plough, but in other places they were covered by from*13 to 18 inches of soil. It is not probable that these walls could have been undermined by worms and subsided, as they rested on a foundation of very hard red sand, into which worms could hardly burrow. The mortar, however, between the stones of the walls of

a hypocaust was found by my son to have been penetrated by many worm-burrows. The remains of this villa stand on land which slopes at an angle of about 3°; and the land appears to have been long cultivated. There- fore no doubt a considerable quantity of fine earth has been washed down from the upper parts of the field, and has largely aided in the burial of these remains. Silchester, Hampshire-—The ruins of this small Roman town have been better pre- served than any other remains of the kind in England. A broken wall, in most parts from 15 to 18 feet in height and about 14 mile in compass, now surrounds a space of about 100 acres of cultivated land, on which a farm-house and a church stand.* Formerly, when the weather was dry, the lines of the buried walls could be traced by the appear- ance of the crops; and recently very exten- sive excavations have been undertaken by the Duke of Wellington, under the superin- tendence of the late Rev. J. G. Joyce, by whick means many large buildings have been

* These details are taken from the ‘Penny Encyclopedia,’ article, Hampshire. discovered. Mr. Joyce made careful coloured sections, and measured the thickness of each bed of rubbish, whilst the excavations were in progress; and he has had the kindness to send me copies of several of them. When my sons Francis and Horace visited these ruins, he accompanied them, and added his notes to theirs. Mr. Joyce estimates that the town was in- habited by the Romans for about three cen- turies; and no doubt much matter must have accumulated within the walls during this long period. It appears to have been destroyed by fire, and most of the stones used in the buildings have since been carried away. These circumstances are unfavourable for as- certaining the part which worms have played in the burial of the ruins; but as careful sections of the rubbish overlying an ancient town have seldom or never before been made in England, I will give copies of the most characteristic portions of some of those made by Mr. Joyce. They are of too great length to be here introduced entire.

An east and west section, 30 ft. in length, was made across a room in the Basilica, now called the Hall of the Merchants (Fig. 9). The hard conerete floor, still covered here and there with tesseree, was found at 3 ft. Section within a room in the Basilica at Silchester. Seale Js. beneath the surface of the field, which was here level. On the floor there were two large piles of charred wood, one alone of which is shown in the part of the section here given. This pile was covered by a thin white layer of decayed stucco or plaster, above which was a mass, presenting a singu- larly disturbed appearance, of broken tiles, mortar, rubbish and fine gravel, together 27 inches in thickness. Mr. Joyce believes that the gravel was used in making the mortar or concrete, which has since decayed, some of the lime probably having been dissolved. The disturbed state of the rubbish may have been due to its having been searched for building stones. This bed was capped by fine vegetable mould, 9 inches in thickness. From these facts we may conclude that the Hall was burnt down, and that much rubbish fell on the floor, through and from which the worms slowly brought up the mould, now forming the surface of the level field.

A section across the middle of another hall in th: Basilica, 82 feet 6 inches in length, called the Civarium, is shown in Fig. 10. It appears that we have here evidence of two with broken tiles” was accumulated. Be- neath one of the layers of charred wood, a valuable relic, a bronze eagle, was found: and this shows that the soldiers must have deserted the place in a panic. Owing to the death of Mr. Joyce, I have not been able to ascertain beneath which of the two layers the eagle was found. The bed of rubble overly- ing the undisturbed gravel originally formed, as I suppose, the floor, for it stands on a level with that of a corridor, outside the walls of the Hall; but the corridor is not shown in the section as here given. The vegetable mould was 16 inches thick in the thickest part; and the depth from the surface of the field, clothed with herbage, to the undisturbed gravel, was 40 inches.

The section shown in Fig. 11 represents an excavation made in the middle of the town, and is here introduced because the bed of “ rich “mould” attained, according to Mr. Joyce, the unusual thickness of 20 inches. Gravel lay at the depth of 48 inches from the surface, but it was not ascertained whether this was in its natural state, or had been brought here and had been rammed down, as occurs in some other places. The section shown in Fig. 12 was taken in the centre of the Basilica, and though it was* 5 feet in depth, the natural sub-soil was not

Section in a block of buildings in the middle of the town of Silchester. reached. The bed inarked “ conerete” was probably at one time a floor; and the beds beneath seem to be the remnants of more here only 9 inches thick. In some other “sections, not copied, we likewise have Light-coloured earth with large pieces of broken tiles, 7 inches. =| Dark, fine-grained rubbish with small bits o1 tiles 20 inches. 4 Fine-grained made ground WY with the débris of older yy Yyyiy jy, »uildings.

evidence of buildings having been erected over the ruins of older ones. In one case there was a layer of yellow clay of very unequal thickness between two beds of débris, the lower one of which rested on a floor with tessere. The old broken walls appear some- times to have been roughly cut down to a uniform level, so as to serve as the founda- tions of a temporary building; and Mr. Joyce suspects that some of these buildings were wattled sheds, plastered with clay, which would account for the above-mentioned layer of clay.

Turning now to the points which more immediately concern us. Worm-castings were observed on the floors of several of the rooms, in one of which the tesselation was unusually perfect. The tesseree here con- sisted of little cubes of hard sandstone of about 1 inch, several of which were loose or projected slightly above the general level One or occasionally two open worm-burrows were found beneath all the loose tessere. Worms have also penetrated the old walls of these ruins. A wall, which had just been exposed to view during the excavations then in progress, was examined: it was built of large flints, and was 18 inches in thickness,

It appeared sound, but when the soil was removed from beneath, the mortar in the lower part was found to be so much decayed that the flints fell apart from their own weight. Here, in the middle of the wall, at a depth of 29 inches beneath the old floor and of 493 inches beneath the surface of the field, a living worm was found, and the mortar was penetrated by several burrows. 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 beneath one of the floors, and of course at a con- siderably 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.”

Section of the subsided floor of a room, paved with tessere, at Silchester. sunk considerably, especi- ally 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 sec- tion, Fig. 13, was taken from north to south across a room, 18 feet 4 inches in length, with a nearly per- fect pavement, next to the “Red Wooden Hut.” In the northern half, the sub- sidence amounted to 53 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 tessera appeared as if drawn a little away from the walls ; whilst

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 3 of an inch above its level. The field, which was in pasture, here sloped from north to south, at an angle of 3° 40’. The nature of the ground on each side of the corridor is shown in the section. It consisted of earth full of stones and other débris, 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 73 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 7f the old wall had been left buried at a little depth “SE ofeog “IO\SOYOTIG “WMOTZUN aetosso} oy} YJouq punosS 04} JO orngeyy ‘aovds 4104s & JO} UMOYS St OpIs YyOvo uo puNoiS poyeavoxo 947 ‘s[[BA SuUIpunog UArop-uayoiqg OT} Opisyng “etosso} YIM poatd “Jops0o B JO JOOY papisqns ay} YySnosyy uoWoos qynos puv yyiou w

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.p. We see in the accom panying 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 pave-: ments 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 section 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

“SE ayeog = ‘pormq 4JO] [TBM PTO oy} Jo suOYYpuNo; oy] WIM ‘podavpue A[JoUMIOJ Uoeq pey YOryar ‘TaSayo|Ig 4B Wool ® JO S|[VM SUIpUNOG UMOP-UEYOIG OY} JO PUL “@iOSse} YL poaed ‘1009 pepisqns oy} Ysnoiyy UO0TZ00g than the other half without any assignable eause. 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 tesselated and often ornamented pavements were laid. The sink- ing 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 ad- mitted 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.

As the foundations of the walls generally lie at a considerable depth, they will either have not subsided at all through the under- mining action of worms, or they will have subsided much less than the floor. This latter result would follow from worms not often working deep down beneath the founda- tions; but more especially from the walls not yielding when penetrated by worms, whereas the successively formed burrows in a mass of earth, equal to one of the walls in depth and thickness, would have collapsed many times since the desertion of the ruins, and would consequently have shrunk or subsided. As the walls cannot have sunk much or at all, the immediately adjoining pavement from adhering to them will have been prevented from subsiding; and thus the present curvature of the pavement is intelligible.

The circumstance which has surprised me most with respect to Silchester is that during the many centuries which have elapsed since the old buildings were deserted, the vegetable mould has not accumulated over them to a greater thickness than that here observed. In most places it is only about 9 inches in thick- ness, but in some places 12 or even more inches. In Fig. 11, it is given as 20 inches, but this section was drawn by Mr. Joyce before his attention was particularly called to this subject. The land enclosed within the old walls is described as sloping slightly to the south; but there are parts which, accord- ing to Mr. Joyce, are nearly level, and it appears that the mould is here generally thicker than elsewhere. The surface slopes in other parts from west to east, and Mr. Joyce describes one floor as covered at the western end by rubbish and mould to a thickness of 284 inches, and at the eastern end by a thickness of only 114 inches. A very slight slope suffices to cause recent castings to flow downwards during heavy rain, and thus much earth will ultimately reach the neighbouring rills and streams and be carried away. By this means, the absence of very thick beds of mould over these ancient ruins may, as I believe, be explained. Moreover most of the land here has hong been ploughed, and this would greatly aid the washing away of the finer earth during rainy weather.

The nature of the beds immediately beneath the vegetable mould in some of the sections is rather perplexing. We see, for instance, in the section of an excavation in a grass meadow (Fig. 14), which sloped from north to south at an angle of 3° 40’, that the mould- on the upper side is only six inches and on the lower side nine inches in thick- ness. But this mould lies on a mass (254 inches in thickness on the upper side) “ of ‘‘dark brown mould,’ as described by Mr. Joyce, “thickly interspersed with small “pebbles and bits of tiles, which present a “corroded or worn appearance.” The state of this dark-coloured earth is like that of a field which has long been ploughed, for the earth thus becomes intermingled with stones and fragments of all kinds which have been much exposed to the weather. If during the course of many centuries this grass meadow and. the other now cultivated fields have been at times ploughed, and at other times left as pasture, the nature of the ground in the above section is rendered intelligible. For worms will continually have brought up fine earth from below, which will have been stirred

up by the plough whenever the land was enltivated. But after a time a greater thickness of fine earth will thus have been accumulated than could be reached by the plough; and a led like the 253-inch mass, in Fig. 14, will have been formed beneath the superficial mould, which latter will have been brought to the surface within more recent times, and have been well sifted by the worms. Wroxeter, Shropshire.—The old Roman city of Uriconium was founded in the early part of the second century, if not before this date ; and it was destroyed, according to Mr. Wright, probably between the middle of the fourth and fifth century. The inhabitants were massacred, and skeletons of women were found in the hypocausts. Before the year 1859, the sole remnant of the city above ground, was a portion of a massive wall about 20 ft. in height. The surrounding land undulates slightly, and has long been under cultivation. It had been noticed that the corn-crops ripened prematurely in certain narrow lines, and that the snow remained un- melted in certain places longer than in others.

These appearances led, as I was informed, to extensive excavations being undertaken. The foundations of many large buildings and several streets have thus been exposed to view, The space enclosed within the old walls is an irregular oval, about 1% mile in length. Many of the stones or bricks used in the buildings must have been carried away ; but the hypocausts, baths, and other underground buildings were found tolerably perfect, being filled with stones, broken tiles, rubbish and soil. The old floors of various rooms were covered with rubble. As I was anxious to know how thick the mantle of mould and rubbish was, which had so long concealed these ruins, I applied to Dr. H. Johnson, who had superintended the excavations; and he, with the greatest kindness, twice visited the place to examine it in reference to my ques- tions, and had many trenches dug in four fields which had hitherto been undisturbed. The results of his observations are given in the following Table. He also sent me specie mens of the mould, and answered, as far as he could, all my questions,

Thickness of mould in : inches. 1. Ata depth of 36 inches undisturbed sand was reached we és se -F mw, 20 2. At a depth of 33 inches concrete was reached 21 3. i = 9 inches concrete was reached 9 Trenches dug in a field called “Shop “Leasows ;” this is the highest field within the old walls, and slopes down from a sub-central point on all sides at about an angle of 2°. Thickness of mould in inches. 4, Summit of field, trench 45 inches deep - 40 5. Close to summit of field, trench 86 inchesdeep 26 6. > n trench 28 inchesdeep 28 7. Near summit of field, trench 86 inches deep 24 8 as xs trench at one end 39

inches deep; the mould here graduated into the underlying undisturbed sand, and its thickness is somewhat arbitrary. At the other end of the trench, a causeway was en- countered at a depth of only 7 inches, and the mould was here only 7 inches thick .. 24 9. Trench close to the last, 28 inches in depth .. 15 10, Lower part of same field, trench 30 inches deep 15 11 ea o trench 31 inches deep 17 12 “s se trench 36 inches deep, at whick depth undisturbed sand was reached 28