Books, Prehistory, Wiltshire Archaeological Magazine Volume 23 1887, Recent Explorations of Silbury Hill by Alfred C Pass

Recent Explorations of Silbury Hill by Alfred C Pass is in Wiltshire Archaeological Magazine 1886 V23.

1887. Recent Explorations at Silbury Hill [Map] By Alfred C. Pass.

SILBURY HILL has been described so accurately by Late Rev. A. C. Smith, in the "Wiltshire Magazine" for 1861, and has been so frequently referred to in this Magazine, that a detailed description of the hill itself would be superfluous. But before describing my recent excavations I will refresh the memories of readers by remarking that it is stated to be the greatest artificial mound in Europe, covering about five acres of ground, it is 125ft. high, and is level on the summit, where it measures diameter.

It is composed chiefly of chalk rubble, which was obtained by excavating the solid chalk rock from the laud surrounding the base Of the mound.

In the belief that this great mound had been raised as a sepulchral tumulus, it has been twice excavated and explored. In the year 1777 the Duke Of Northumberland brought miners from Cornwall, and sunk a shaft from the summit to the base of the bill. In 1849 the Arehæological Institute caused a tunnel to be made from the south side to the centre of the hill, when the original nucleus or central point was found, but no trace of sepulture was discovered. A few fragments Of deer's horns and some pieces of twisted grass only rewarded their search. The deer's horns were, perhaps, the broken tools used in excavating the chalk rock, of which the hill is chiefly composed, and the twisted grass may have been remains of the baskets in which the chalk was carried on the heads of the builders. From the results of this examination, it may be inferred that the mound is not sepulchral. If it had been, then, surely, in the central point from which the hill was started, one would expect to find some remains of the great dead in whose honour it was erected.

In describing the tunnel of 1849 the Dean of Hereford, in his "Diary of Dean", says:- "Nothing could be more evident than the existence of the primary heaping of the mound, through the centre which, or very nearly so, the elevated tunnel was cut.

"At the floor of this, was traceable the line of the original turf of the natural hill, and it was clear to demonstration that this had been cut through. No cist, therefore, bad been found below that line in any part yet examined. One thing is manifest, that the examination of 1777 did not hit the actual centre the tumulus, whilst "we had excavated its very core"

Now, had this mound been erected simply as a monument, we should expect to find it placed on an elevated situation, where it could be seen from afar; but, on the contrary, it Was erected upon very ground, at the very bottom of a gently rising down, and this fact bas been referred to by Duke, who, in his "Druidic Temples," says "This peculiar spot is a hollow nearly surrounded on all sides with moderately rising ground," and also by the Rev. A. C. Smith, who, in his "Silbury," says "Standing as it does on low ground, and surrounded with undulating downs, which tower above it, very limited indeed is the view from the summit." Had it been raised on the summit of one of these "undulating downs" it would have been visible for many miles around. The barrows in this neighbourhood are situated on the hill tops, and term remarkably prominent objects in the landscape.

A special survey Of Silbury Hill has been made for me by Messrs. Ashmead & Son, of Bristol, and the accompanying plates are copied from the plans prepared by them. It Will be seen that the boundary line of the excavated area (from whence all the material used for building the hill was obtained) extends in the form of a circle nearly surrounding the base of Silbury Hill at a distance of about a bundred feet on the north and east, but on the west it includes a much larger area. The southern boundary of meadow west of the hill, is steep escarpment form«l by the removal of the chalk from the rising down. Here chalk has been removed to a depth of over from the original surface of the down (as shown Plan 2).

On the south of the mound, a deep trench separates the mound from the adjacent high ground, but across this trench a ridge of chalk rock was allowed to remain, when all the rest was removed. This formed a causeway, and appears to have been the only way of approach to the hill from the adjacent high ground. Even between the end of this causeway and the hill, there was a great gap of some depth.

The bottom of the deep trench, to the south of the mound, has been considerably raised by infilling of earth washed from the turnpike road, which runs alongside it. This land belongs to another owner, so that I could not dig here; but I would suggest to the Wiltshire Archæological Society the desirability of sinking two or three shafts through the wash, down to the chalk, and thus to find the original depth of the trench here; and also to ascertain, by digging, whether the eastern causeway or projection forms any part of the original structure. I am inclined to think this may simply be composed of material deposited here, when the level of the turnpike road was lowered in the last century. This could easily be proved by ascertaining whether this projection is composed of solid chalk rock, or of loose material which has been brought here. A little below the top of the hill, and nearly surrounding it, is a ledge or terrace. This may be either a part of the original design, and may have formed the base of a stockade or defence of some kind; or it may have been formed by the slipping down of the outside materials of the hill. This point deserves examination. Fergusson, in Rude Stone Monuments," says Nothing would surprise me less than if five or six entombments were found arranged around the upper plateau, at a small depth below the surface."

The mystery of its origin; Who built it? For what purpose? When? were questions which vividly presented themselves to me the first time I visited Silbury Hill, some years ago, on a lovely brilliant day in June. When looking down from the summit of this great mound, I was struck by the well-defined line, plainly marking out the limit of the space, from whence the materials had been excavated for making the hill. This area is below the level of the adjacent ground, and the grass grows there of a brighter green, perhaps owing to a greater amount of moisture in the soil. Since then, it occurred to me that an excavation in this meadow at the base, would disclose the depth from which the chalk had been removed, and might also throw some light on the origin of the hill; so last summer (1886) I applied to the owner of the meadow, Mr. Pinniger, who readily gave me leave to sink a shaft there, and afterwards he very kindly extended this permission, so that in the autumn I was enabled to have ten shafts sunk in the meadow, to the west and north of the hill.

In sinking all the shafts, the men first dug through about a foot of dark surface-soil, and then through white clay until the undisturbed chalk rock was reached, this solid chalk being, of course, the limit of the depth of the excavated material originally used in constructing the mound. At the bottom of two of the shafts (Nos. 1 and 8) marks of the original workers were distinctly visible, in the form of notches or steps in the chalk rock. The measurements of these holes, show that the chalk had been removed in most places to a depth of about 15ft, but near the foot of the hill this depth suddenly increases to about 21ft., below the present surface, and this has all been replaced by alluvium.

Near the mound, the alluvial clay in the moat contained a large admixture of chalk rubble, which has rolled from the hill; but further from the mound, at shaft No. 6, not one fragment of chalk rubble could be seen; the entire depth of 15ft. consisted of fine white tenacious clay, with a few fractured flints, and some bones.

The only large stones found were met with in shaft No. 2, near the causeway: here, mingled with the clay and chalk rollings, were many sarsen stones, 10in. to 14in. in diameter.

A very large part of the chalk used in making Silbury Hill was obtained from the west side; Where, in addition to the trench 100ft. wide, a large area has been excavated to a depth of 15ft. or 16ft. All the chalk and earth required for making this great mound was probably carried in baskets, on the heads of men, women, and children, from the trench, although it could have been obtained with far less labour from the high ground to the south, had there not been some motive which led the builders to obtain the materials from this great depth, near the base of the mound.

It may appear strange that the hill was formed by this method, but in our own day vast railway embankments, in Europe and India, have been thus formed. Sir Thomas Brassey, in his book, Work and Wages," refers to The Italian villagers, men, women, and children, carrying earth in baskets on their heads to construct railways.

My excavations were commenced in the month of September, after a long continuance of dry weather, so that the adjacent little stream—the Kennet—had been dried up for more than two months; yet water continually stood to the depth of 8ft. in the deep holes which were sunk in the trench, at the foot of the mound, and I think it would never at any time of the year fall below that level.

The large area to the west of the hill, although not excavated to so great a depth as the trench, must necessarily have been a pond of water during a great part of every year.

These facts have hitherto escaped observation, but it was from a surmise that such would prove to be the case that I was first led to attempt these explorations.

It is clear that the intention of the builders was to completely isolate the hill, and prevent all approach to it from the surrounding ground.

For what purpose was this moat intended? There is one reason probable, and that is for the purpose of defence. By surrounding the hill with water, it could be approached only by the narrow causeway situate on the south side; and this could have been stockaded as a further defence. The top of the hill, also, may have been surrounded by a stockade, and the hill would then have somewhat resembled a New Zealand pah. My conclusions are, that the builders of this mound, selected its peculiar low situation, for the sole purpose of obtaining the line of defence furnished by the water in the surrounding moat; and that Silbury Hill was erected as a tribal stronghold, or place of retreat and defence, in case of a sudden attack by enemies. If not meant for defence, for what purpose was this deep trench intended?

The mound at Marlborough [Map] strongly resembles Silbury Hill, and was erected in a similar low situation, near the same stream—the Kennet—possibly by the same race of men, for the same purpose; and it would be a matter of much interest to ascertain whether the base of the Marlborough mound had been originally surrounded by a deep trench, in depth so far below the level of the Kennet as to have always contained water. This could be ascertained by sinking some Shafts there.

In the course of these explorations an unexpected and interesting discovery was made, which throws light on the date of the erection of the mound. In shaft No. 5, after passing through 9 ft. of white alluvial clay, the men came to a distinct blackish layer about a foot in thickness, consisting of the usual tenacious clay, with a large admixture of charcoal, fractured flints, bones, and small burnt sarsen stones, all evident indications of human occupation. The whole of this layer I had carefully set aside, and then washed it in water through a sieve. By this means all the clay was the residue was then carefully examined for traces of human workmanship. Besides many other flints, one well-worked flint inptement rewarded this search (see plate). Also in another shaft (No. 6) flint flakes were found in the alluvium. These flints I sent to the great authority upon flint implements—Mr. John Evans, D.C.L., P.S.A., who kindly examined them, and wrote as follows "The flints from No. 5 shaft are, I think, all artificial. One, which is very well wrought, may be either an unfinished arrow-head, as you suggest, or a small knife such as is sometimes found in the interments in barrows. The flakes are probably the waste pieces from chipping out some large tools, though some of them have been used as instruments for cutting and scraping. The evidence you have obtained shows that flint has been in use, since Silbury Hill was formed, for cutting instruments, for I think that the knife or arrow-head from shaft No. 5 must be accepted as probably not later than the Bronze Period, to which most of our flint arrow-heads belong"; and further think that any doubt that may have existed as to the mound being pre-Roman may now be dispelled."

These finds reveal the important fact, that long after Silbury Hill had been erected, the neighbourhood was inhabited or visited by a people who made and used flint weapons. The date was so long after the formation of this mound that not less than 5ft. of alluvium had accumulated in that part of the trench which these flint-workers occupied when they temporarily encamped there, lighted their fires, cooked their food, and formed their flint weapons; and the depth of this accumulation would imply a considerable lapse of time.

The time of their stay must have been either summer or autumn, for in the spring and winter months the level of their encampment, which is 9ft. under the present surface of the meadow, would be always under water, because it is much below the level of the: adjacent stream, which forms the only drainage for this district. In the winter of every year this meadow is, even now, frequently submerged by the overflow of the stream.

Besides their weapons, these flint-men left behind some remains of the animals which supplied them with food, and Professor Lloyd Morgan has identified the bones of deer, ox, and pig; also of man's faithful companion, the dog. We may infer that some of their food was cooked by boiling, for the small sarsen stones found associated with the other remains have all been burnt, and probably have been used as pot-boilers.

More remarkable still, there was found, in this black layer, a human bone which had been broken into two pieces. It is a femur possessing peculiar characteristics of some interest, from the fact of the linea aspera being developed to a very unusual extent. I wish to direct attention to the lower jaws, aud to the fragments of bones, from this black layer. These fragments are just such small hard pieces as we now see left uneaten by dogs; and they are evidently the dogs' leavings. Sir John Lubbock, in his account of the Danish kitchen-middens, describes a similar fact, and he alludes to the frequent occurrence of the lower jaws of animals which the dogs had there left uneaten.

In every shaft but one, many bones of animals were found in the alluvium, at all depths. Professor Lloyd Morgan has kindly examined these, and, with the exception of those bones found in the black layer, pronounces that they belong exclusively to ox and deer. It is remarkable that not any bones of sheep were found in these excavations, although that animal has for many centuries been most abundant in Wiltshire.

In addition to the objects already referred to, a brass coin of Marcus Aurelius was found, 6ft. under the surface, in shaft No. 2, and in another shaft an iron arrow-point was found; these things, however, bear but little on the date of the mound.

The idea entertained by some antiquarians, that the shape of the summit and slope of the hill were altered owing to the large quantity of material excavated from the shaft in 1777 is not borne out by the fact. This shaft was 4ft. in diameter, and the whole of the chalk debris removed could not have exceeded forty cubic yards, and this would occupy but a small space in the centre of the summit of the hill—over 100ft. diameter, so that none of it would have rolled down the hill sides. In fact all this material appears to have been refilled into the hole, excepting a small bank which is still visible on the flat summit.

As the outcome of these excavations I have ascertained that Silbury Hill was originally surrounded by a deep trench, or moat, at all times containing water.

Also, that it was erected by a people, probably a rude race of hunters, so little advanced in civilization, that they were using flint implements a long time after the hill was built; this discovery places the date of the erection of Silbury Hill at a very early period, probably some centuries before the arrival of the Romans in Britain.

It does not follow that the builders of Silbury Hill were actually the same race as the flint-workers, whose traces were found in the trench. A long interval of time must have necessarily elapsed to account for the deposit of 5ft. of alluvium; so these men may have supplanted some previous race of dwellers; but, if this be so, it carries back the date of the erection of Silbury Hill to a still more remote period.

Note.—All the objects of interest found in these excavations have been sent to their proper resting-place, the Devizes Museum.


Details of the ten shafts. The numbers refer to the numbers on the annexed plan, and the depth of water stated is the height to which water stood in those shafts, at the end of the long dry season, before the rains commenced.

Shaft No. I.—19ft. to 20ft. deep. White alluvial clay with a large admixture of chalk rollings. In this shaft stags' horns were found, and in no other. At the bottom the chalk rock showed traces of the original workers, the chalk being notched into steps, about a foot difference in level. The same kind of marks was found in shaft No. 8.

Shaft No. 2.—21½ft. deep. White alluvial clay containing much chalk rubble, also some sarsen stones I Oin. to 14in. diameter. In this shaft, at 6ft. under the surface, was found a brass coin of Marcus Aurelius. Water rose in this shaft 8ft. deep.

No. 3.—3½ft. only!

No. 4.—4ft. only!

A projecting mass of chalk for some reason has not been removed at this point. Was this left as a sloping access to the hill, for carrying the material during the erection?

No. 5.—15½ft. This was the first shaft sunk. The first 3ft. to 4ft. under the soil was white alluvial clay, then clay with a mixture of chalk rubble. At 9ft. under the surface a distinct black layer, about 1ft. thick, containing fractured flints, bones, burnt sarsen stones, and charcoal. Then, below this layer, 5ft. of alluvial clay and chalk rubble to the bottom.

Shaft No. 6.—15ft. deep. This shaft, after the surface soil, passed only through a fine tenacious white clay, containing no chalk rubble. A few flints, flakes and broken flints, and some bones, were scattered through this clay. The bottom 9in. contained a large quantity of flint fragments. The absence of chalk rollings or rubble may be attributed to the great distance of this shaft from Silbury Hill. The white fine clay, when analysed, was found to consist of chalk 88½%, insoluble silica 11½%.

No. 7.—Sunk at the extreme west limit of the meadow, was only 6ft. deep. White alluvial clay and chalk rubble. No bones were found in this shaft.

No. 8.—16ft. deep. Upper half tenacious discoloured clay, not pure white; lower half white clay, containing some chalk rollings. The bottom of this shaft showed traces of the old workers, in the form of notches or steps.

No. 9.—Was sunk 16½ft., and then a bar driven a further 5ft. did not reach solid chalk. This shaft and No. 10 had to be abandoned before completion, owing to the rain in November rendering the sides unsafe for the workmen. Passed through only alluvial clay, discoloured and containing many freshwater shells.

No. 10.—As far as sunk all alluvial clay, pale brown colour, containing many shells, no chalk rubble. This clay evidently was mixed with earthy deposit from the stream. Animal bones were found in the alluvial deposit in every shaft excepting No. 7 only.