Sep 27

Wincobank, South Yorkshire

Wincobank – Sheffield

1903 OS map of Wincobank

Location

Wincobank (W.R.), Hillfort (SK/378910)
2.5 miles NE of center of Sheffield. Finds in Sheffield Museum.

Description

“This is an oval fort with an internal area of 2.5 acres. A bank, ditch and counterscarp bank are continuous around it except on the N side where ditch and counterscarp have been destroyed. The banks now nowhere exceed 3 ft. in ht. There is an entrance on the NE side, where one end of the main bank is thickened and the other end runs out across it for 30 ft., forming a type of out turned entrance.

Excavation in 1899 showed that the ditch had an original depth of 5-6 ft. The main bank has a rubble core with stone facings. It had contained much timber work holding it together; at some period this had been burnt, accidentally or otherwise, until much of the rampart had been fused into a solid mass by heat. Not dated.” – N Thomas, Guide to Prehistoric England.

Part of the southern Rampart, and the view to the south from Wincobank

“The oval 2.5 acre fort at Wincobank, north of Sheffield, almost certainly provides an example of timber-laced rampart construction. Excavations in 1899 (Howarth, 1899) indicated that the internal rampart, surviving to a height of about 3 feet, was 18 feet wide, and had well-built stone revetments. The core was of sandstone rubble, badly burnt and in parts fused, with variable quantities of charcoal and burnt timber. There was an outer earthen rampart with a little burnt wood and burnt stones, and a ditch between the two ramparts. No material remains were found.” Later Prehistory from the Trent to the Tyne. Challis and Harding 1975.

Research notes

Wincobanks virtrified inner rampart.

Site visit notes – George Chaplin

I was told about Wincobank by my father in law, who said it was vitrified. When I visited the first bit of rampart I looked at had indeed been fired. I’ve made lots of fires in my time and the top layer of rock reminded me of rock which had been in an intense fire for several days – we used to have the the biggest bonfire around and I was chief fire lighter! I’d call this type of rock example A, I took a chunk of it. As I walked round the inner rampart (this fort looks like it has two ramparts) I could see that this seemed to have been subject to the same temperatures along the entire length of the rampart covering the entire circumference of some 430m and formed a layer which was 3-4 ft wide.

The burnt effect was graduated, with those rocks on the outside of this layer apparently reaching a cooler heat than those in the middle of this layer. Possibly showing that the rocks which were originally on the top of the rampart reached a higher temperature.

As I walked along the rampart I could see many areas where the rock had almost melted and had certainly fused with other rock I also got a sample of this kind of rock (Example B).

Looking at the samples, example B seems to be several pieces of rock which have bonded together, they all show surface bubbling with bubble diameters of between 1 and 5 mm. Rather than being reddish like example A, example B is much blacker and very black in places

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1857 map of Wincobank, shown on the bottom left. Of interest is its relationship to Roman Rig, identified on the upper right.

Research Notes

“This is an oval fort with an internal area of 2.5 acres. A bank, ditch and counterscarp bank are continuous around it except on the N side were ditch and counterscarp have been destroyed. The banks now nowhere exceed 3 ft. in ht. There is an entrance on the NE side, where one end of the bank is thickened and the other runs out across it for 30 ft., forming a type of out-turned entrance.

Excavation in 1899 showed that the ditch had an original depth of 5-6 ft. The main bank has a rubble core with stone facings. It had contained much timberwork holding it together; at some period this had been burnt, accidentally or otherwise, until much of the rampart had been fused into a solid mass by the heat. Not dated.” Guide to Prehistoric England, Nicholas Thomas, 1960.

Sep 27

Almondbury Hill Fort

View of Castle Hill, Almondbury, as it looks today with the Victorian tower on the top. Also Varley plan of Almondbury.

Another plan of Almondbury, showing the outer ditches

Sep 27

Tap O’Noth, Inverurie

Tap O’Noth

Grid ref: NJ 484 293 Ordnance Survey Landranger series sheet no. 37

20 miles W of Inverurie. The approach to this, the second highest fort in Scotland, involves a somewhat arduous walk from Brae of Scurdargue, approximately 1 ½ miles NW of Rhynie on A941 to Dufftown.

The site crowns the conspicuous 562 m high SW summit of the Hill of Noth. The major feature is the substantial remnant of the vitrified wall, defining an oblong approximately 100 m by 30 m in size. An internal depression, in which water may sometimes be seen, probably served as a cistern for the initial inhabitants. Although it is difficult to imagine such a high site being occupied on a permanent basis, there are slight traces of platforms, perhaps for circular wooden houses, on the S side beyond the collapsed rubble from the vitrified enclosure. Much further out, on the N and E, there is a much less impressive defence, formed by boulders strung out along the flanks of the hill.

This is one of the best examples of a vitrified fort, it is near the village of Rhynie in northeastern Scotland. This massive fort from prehistory is on the summit of a mountain of the same name which, being 1,859 feet (560 metres) high, commands an impressive view of the Aberdeenshire countryside. At first glance it seems that the walls are made of a rubble of stones, but on closer look it is apparent that they are made not of dry stones but of melted rocks! What were once individual stones are now black and cindery masses, fused together by heat that must have been so intense that molten rivers of rock once ran down the walls.

Sep 27

Dunnideer, Aberdeen

Dunnideer – Vitrified Fort

Grid ref: NJ 612 281 Ordnance Survey Landranger series sheet no. 37

12 miles NW of Inverurie. Access to the group of monuments on Dunnideer Hill is by a signposted footpath from minor road from Insch to Clashindarroch Forrest about 1 mile W of Insch , off the B 992.

The Medieval Castle, the most prominent feature in the hill, stands inside, and is built from the debris of, an oblong vitrified fort, a maximum length approximately 70 m, which crowns the summit. Outworks, most clearly marked on the E, may be associated with this phase. Early features in the interior include a depression adjacent to the castle, which is probably the remains of a cistern or a well. A rectilinear building, set at right angles to the main axis of the vitrified fort, is certainly later in date. Further out and downslope, traces of slight banks and ditches can be noted: these represent an unfinished defensive scheme, almost certainly later in date than the vitrified fort. On both the N and S slopes, traces of what appear as small grass-covered quarry scoops, fronted by level platforms c 8 m in diameter, can be noted. These represent the stances for timber round-houses which may date from as early as 1200 BC.

Sep 27

Clickhimin, Shetland

Clickhimin Broch

Location: 1 mile SW of Lerwick, Shetland.

Owner: Historic Scotland

This site was occupied in several periods, originally late Bronze age between 700 – 500BC. Firstly a simple farmstead which expanded to a blockhouse (fort) and then by a huge circular brock. A population of around 60 lived in this little fortress. Later, 2nd century occupation is shown when a wheelhouse was added.

The fort and broch at Clickhimin display a sequence of development
from the later Bronze Age to the later 1st millennium AD

“Shetland falls outside the range covered here, but the monogragh on Clickhimin is of primary importance, not only for the details of the excavation of the small fortress, but because it sets out a convincing hypothesis as to the nature and origins of the ‘vitrified’ forts of the Scottish mainland.” – AHA Hogg, Hill-forts of Britain.

Clickhimin, it appears is not a vitrified fort, the above reference was made in the light that it may be one of the oldest timber framed ramparts in Scotland. It has been suggested that all vitrified forts were timber framed.


Excavations at Clickhimin by J R C Hamilton.

Sep 27

Craig Phadrig, Inverness

Craig Phadrig – Vitrified Fort

Region : Scottish Highlands
District : Inverness
Town or village : Inverness
Grid Reference : NH 640 452
Period : 500 BC-AD 600

Craig Phadraig is a hilltop fort within a Forestry Commission plantation, 2.5km west of Inverness. It occupies a position with excelent views over the Beauly Firth. The rectangular area enclosed within the ramparts measures 75m x 23m. Radiocarbon dating indicates that the fort was built in 5th or 4th century BC.
The site comprises two steep ramparts, which are mainly grass grown. These were constructed of timberlaced stonework and then burnt, producing extensive vitrification. A vitrified part of the wall can be seen near a pine tree at the northern end.

The ramparts are grass covered, the inner stand 4m high externally and 1m internally, the ruined rasmparts spread some 10m in width. No entrances to the inner rampart have been found. The interior of the fort has an area of 0.2 hectares..

The outer rampart is much slighter, a mound in the eastern corner may be natural.

Excavation in 1971 has produced evidence of re-occupation in the time of the Picts, 6th century AD.

Inner rampart of Craig Phadrig

Research Notes

“The construction of the circling rampart at Craig Phadrig has been examined in detail and the basic principles there established probably apply to all forts within the Inverness area. The total thickness of the wall at Craig Phadrig was just under 21 feet (6 m.) and on the basis of the quantity of the collapsed debris still remaining, must have originally stood at least 26 feet (8 m.) high. The rampart consists of two revetments enclosing a rubble core. All stone was obtained locally if available, by surface collection, although for some forts (including Craig Phadrig?) quarrying must have been essential, particularly for suitable blocks for the revetment

The rampart was founded on the natural turf, no previous preparation having been undertaken except the marking out of the line of the wall. In some cases it is suggested that the rampart was founded on a raft of logs, but no examples of this type appear in this area. The revetting walls were carefully constructed, each occupying about one-third of the total width of the wall at the base, and gradually thinning as the structure reached its full height. The lowest yard (m.) is invariably constructed of very large blocks to provide an adequate foundation, while above this smaller blocks were used, and frequently timber lacing was introduced into the design. Clear evidence of horizontal timber beams running from the inner revetment into the core was found at Craig Phadrig, and circumstantial evidence supports a network of horizontal, transverse and vertical limbers tying the inner revetment thoroughly to the core. Although timber beams appear in the outer face of some continental forts, they never did so at Craig Phadrig. Besides its value in tying revetment to core, limber lacing has the advantage of preventing a large section of the core “running” should the outer revetment be breached by attackers. If that happened, a natural causeway would be provided for the invaders. Furthermore, timber lacing has the properly of spreading the weight-load in a massive structure. Brochs built entirely of dry stone, without any timber lacing, frequently show intensive shattering and cracking of stones in the lower courses due to the pressure from above.

Small finds and continental parallels were the original dating criteria for fixing these forts firmly within the Celtic Iron Age, and the use of radio-carbon dates on the Scottish forts in the last decade has confirmed the date for Craig Phadrig, to be 350 B.C.; Craig-marloch Wood. The evidence from several sites, including Craig Phadrig. Suggests that the primary fort survived for a relatively short time, and was refurbished later.

“A preliminary examination of the bones from Craig Phadrig shows a high proportion of red deer, and also possibly reindeer. The European wild boar is also recorded. Of the pastoral animals, cattle were by far the most important.” The Hill Forts of the Inverness Area, ALAN SMALL

Sep 27

Vitrified Forts Distribution

Georgraphic Distribution

One of the great mysteries of classical archaeology is the spartan worldwide distribution of vitrified forts with the exception of Scotland..

Scotland

There are at least 50 such forts throughout Scotland. Among the most well-known are Dunnideer, Craig Phadraig (near Inverness), Abernathy (near Perth), Dun Lagaidh (in Ross), Cromarty, Arka-Unskel, Eilean na Goar, and Bute-Dunagoil on the Sound of Bute off Arran Island. Another well-known vitrified fort is the Cauadale hill-fort in Argyll, West Scotland.

Others include, Dun Mac Uisneachain (Dun Macsnoichan), the ancient Beregoiium, about 9 m. N.N.E. of Oban; Tap o’ Noth, in Aberdeenshire; Craig Phadraic, or Phadrick, near Inverness; Dun Dhardhail (Dunjardil) in Glen Nevis; Knockfarrail, near Strathpeffer; Dun Creich, in Sutherland; Finhaven, near Aberlemno; Barryhill, in Perthshire; Laws, near Dundee; Dun Gall and Burnt Island, in Buteshire; Anwoth, in Kirkcudbright; and Cowdenknowes, in Berwickshire. Dun Mac Tjisneachain is the largest in area, being 250 yds. long by 50 yds. broad. In Barryhill and Laws the remains of small rectangular dwellings have been found.

The evidence from elsewhere shows very few vitrified forts elsewhere, indeed the total number of vitrified forts worldwidde is thought to be less than 100. Some examples are as follows:

France

Vitrified forts in France are discussed in the American Journal of Science (vol. 3, no. 22, 1881, pp. 150-151) in an article entitled “On the Substances Obtained from Some ‘Forts Vitrifiés’ in France”, by M. Daubrée. The author mentions several forts in Brittany and northern France whose granite blocks have been vitrified. He cites the “partially fused granitic rocks from the forts of Château-vieux and of Puy de Gaudy (Creuse), also from the neighbourhood of Saint Brieuc (Côtes-du-Nord)”. Daubrée, understandably, could not readily find an explanation for the vitrification.

Turkey

Similarly, the ruins of Hattusas in central Turkey, an ancient Hittite city, are partially vitrified. The Hittites are said to be the inventors of the chariot, and horses were of great importance to them. It is on the ancient Hittite stelae that we first see a depiction of the chariot in use. However, it seems unlikely that horsemanship and wheeled chariots were invented by the Hittites; it is highly likely that chariots were in use in ancient China at the same time.

Iran

Some of the ancient ziggurats of Iran and Iraq also contain vitrified material, sometimes thought by archaeologists to be caused by the Greek fire. For instance, the vitrified remains of the ziggurat at Birs Nimrod (Borsippa), south of Hillah, were once confused with the Tower of Babel. The ruins are crowned by a mass of vitrified brickwork–actual clay bricks fused together by intense heat. This may be due to the horrific ancient wars described in the Ramayana and Mahabharata, although early archaeologists attributed the effect to lightning.

Other locations

Vitrified forts have also been found in Yorkshire and Lancashire, in England; Londonderry and Cavan, in Ireland; in Upper Lusatia, Bohemia, Silesia, Saxony and Thuringia; in the provinces on the Rhine, especially in the neighbourhood of the Nahe; in the Ucker Lake, in Brandenburg, where the walls are formed of burnt and smelted bricks; in Hungary.

Sep 27

Why Vitrify a Fort?

Why was it done and by whom?

Practical reasons?

Originally it was thought that the forts had become vitrified due to an enemy attack. A theory proposed by Childe in the 1930 thought it was that it was invaders, not the builders, who were assaulting the forts and then setting fire to the walls with piles of brush and wood; however, it is hard to understand why people would have repeatedly built defences that invaders could destroy with fire, when great ramparts of solid stone would have survived unscathed. Also this theory does not stand up to the geographic distribution of hill forts versus the known warring area where hill forts were in use. For example the south of England suffered wave after wave of hostile invasion from other Gaullish tribes yet no vitrification has been noted – surely if it was a natural effect of a battle then these forts would be more likely to occur in the south of England (given the large concentration of timber laced ramparts and the frequency of fighting in the area).

This idea was amended with the theory that the builders of the walls had designed the forts in such a way that the vitrification was purposeful in order to strengthen the walls. This theory postulated that fires had been lit and flammable material added to produce walls strong enough to resist the invading armies of the enemy. It is an interesting theory, but one that presents several problems. The main problem with this theory is there is no indication that such vitrification actually strengthens the walls of the fortress; rather, it seems to weaken them. In some cases, the walls of the forts seem to have collapsed because of the fires, however this may show an error in the calculations of the builders.

To further illustrate this point, Julius Caesar described a type of wood and stone fortress, known as a murus gallicus, in his account of the Gallic Wars. This was interesting to those seeking solutions to the vitrified fort mystery because these forts were made of a stone wall filled with rubble, with wooden logs inside for stability. Caesar notes how the flexibility of the wood adds to the strength of the fort in case of battering ram attack.

Some researchers are sure that the builders of the forts caused the vitrification. Arthur C. Clarke quotes one team of chemists from the Natural History Museum in London who were studying the many forts:

“Considering the high temperatures which have to be produced, and the fact that possibly sixty or so vitrified forts are to be seen in a limited geographical area of Scotland, we do not believe that this type of structure is the result of accidental fires. Careful planning and construction were needed.”

Our own research into how forts were vitrified does indeed suggest a deliberate and planned action on behalf of the builders. Looking at the hill forts in evidence today it appears that although many seem to be specifically built in strategic locations some do not take full advantage of the natual defences available. Another common feature is that many vitrified forts have two rings of ramparts, but only the inner is vitrifed. This suggests that the vitrified rampart was for the benefit of the forts users (not visible outside the fort) and that although linked with battle, the vitrification served a purpose other than strengthening the fort.

Beyond this reasoning any further comment is pure speculation, but our research does indicated that the vitrification process could have been part of a lengthy ‘ceremony’ and will have been directed by the most powerful members of the community. Although it is strongly felt that vitrification of forts represents a cultural or religious element, further comment is reserved until further investigative work can be performed.

Sep 27

How to Vitrify a Fort

Vitrification of Hill Forts

The Vitrification process

Vitrification as seen in hillforts is where the surface of the rampart has been heated to temperature that the stone has melted and bonded with its neighboring stone. In some cases forming a glassy surface.

The theoretical and limited practical attempts to recreate vitrification have largely been inconclusive, since significantly more effort was required to melt the rock than was expected. This has revealed several problems which our assumptions so far.

The use of imported sandstone to create the vitrified rock gives shows that the fort builder knew how to select rock specifically for its vitrification properties and shows that vitrified forts were definitely planned to be so, and therefore that other techniques will have been used to produce the desired effect. So far science has largely overlooked this and assumed more or less simple or un-planned fires causing vitrification.

The problem lies in concentrating the heat, simply having a very large fire close to an appropriate stone face will not easily vitrify the rock. For example when a fireplace is heated, the burning temperature of wood is at it´s highest from 800 to 1200 ºC, which should be hot enough to melt stone (1100 ºC) but according to studies carried out by Nunnanlahden Uuni Oy, the surface of hottest stones heats up to only 650 ºC in normal use. This shows the difficulty in getting a simple (but large) open fire to cause vitrification.

Some other points are worthy of mention. In the many cases of vitrification, it has been noticed that the rock applied to the rampart was of much smaller – stone fragments, it has been suggested that this was to increase the surface area of the vitrification rock and there increase the heat absorption. It also however indicated that an additional substance would have been required to hold these smaller fragments in place while they melt and adhere to the main body of the rampart.

Additionally, in some vitrified sites there is evidence that salt may have been used to increase the temperature of the fire, although this evidence is rare (France only) it may explain the largely coastal orientation of the Scottish forts.

Clearly if ancient man were prepared to go to such lengths in preparing the surface of the rampart ready for vitrification then other techniques would have been adopted which may have been overlooked in research assumptions to date.

In is our proposal therefore that in order to vitrify a fort, ancient man left nothing to chance. Having assessed the melting characteristics of the rock (with a test burn) and aquired additional more suitable facing rock if needed. The Rampart was prepared by the application of the surface stones, together with an additional flux-like compound which improved the adhesion and melting characteristics of the rock.

Once this was in place, the entire rampart was turned into an enormous kiln, by using clay to build a vented tunnel around the rampart, probably with multiple burning points and flues. This allows the heat to be amplified and directed towards the rampart, thus achieving the even vitrification that has been noted. Iron age kilns were more than capable of reaching the desired temperatures.

To date there is no evidence of the kiln technique being used, since it is likely that the clay kiln will have been designed to be fully removed such evidence is unlikely to be forthcoming. However we feel that this is the most likely method of creating a vitrified rampart since; It uses technology well known in the period; Once perfected, the technique would allow for the controlled even application of the effect which has been observed; It uses down to earth ordinary technology to provide the desired effect.

It is also likely that the preferred wood for the vitrification process would have been Oak and Yew, as these were readily available and have high burning temperatures

One other theory worthy of mention because of its historic interest rather than likely-hood is that the forts came under attack from “Greek Fire”.

Greek Fire

In ancient times there was a substance known through writings as Greek fire. This was some sort of ancient napalm bomb that was hurled by catapult and could not be put out. Some forms of Greek fire were even said to burn under water and were therefore used in naval battles. (The actual composition of Greek fire is unknown, but it must have contained chemicals such as phosphorus, pitch, sulphur or other flammable chemicals.)

“Greek Fire was the secret weapon of the Eastern Roman Emperors. It is said to have been invented by a Syrian Engineer, one Callinicus, a refugee from Maalbek, in the seventh century (673 AD). The “liquid fire” was hurled on to the ships of their enemies from siphons and burst into flames on contact. As it was reputed to be inextinguishable and burned even on water, it caused panic and dread. Its introduction into warfare of its time was comparable in its demoralizing influence to the introduction of nuclear weapons in our time. Both Arab and Greek sources agree that it surpassed all incendiary weapons in destruction. The secret behind the Greek fire was handed down from one emperor to the next for centuries. Rumors about its composition include such chemicals as liquid petroleum, naphtha, burning pitch, sulphur, resin, quicklime and bitumen, along with some other “secret ingredient”. The exact composition, however, remains unknown. For a thorough investigation of the weapon one can refer to Professor J.R. Partington’s book, “A history of the Greek Fire and Gunpowder”, Heffer, 1960. This volume quotes the ancient authorities extensively, with an excellent commentary. It also examines ancient and modern theories on the composition of the chemicals used in the Greek Fire. This is considered the most up to date source on the subject. “

Sep 27

Classification of Vitrified Forts

Exploration of vitrified fort classification

Currently, there is a single grouping of vitrified forts, it is our contention that in reality only a few forts should be classified as such, and that analysis would be helped if this classification was further refined. In order to perform better asnalysis of vitrified forts, it will be neccesary to attempt to classify the various features, the following discussion examines some possible options.

General Classification

1. Partially Vitrified or burnt forts where isolated areas of the fort are affected.
2. Totally Vitrified forts which have large areas of even vitrification..

Partial vitrification can occur where an intense heat causes vitrifaction in one or more isolated locations along part of the rampart, or where the temperatures were never so high as to cause the rock to melt. Such forts could include  Almondbury in Yorkshire where the excavation evidence indicates the fire started from a small area and the heat involved may not have been as high as 600 C. The causes of such vitrification and burning could be the result of attack or from accidental fire damage due to gateways or buildings burning in a prolonged and uncontrolled manner. In these cases it is probable that relatively small areas of burnt stone may occur, however it is our conjecture that since the design of the rampart meant fire would spread only with difficulty and would be easily doused by the inhabitants of the fort.

that ese types of forts from forts which are Totally Vitrified. Also included in this classification are forts which have been burnt as a result of a battle, the reason for this is that the intense heat required to cause the sorts of vitrification observed could only be the result of careful planning, it is not likely that enough fuel would have been easily to hand.

Total vitrification appears to be the application of an extreme temperature evenly throughout the entire length or significant section of the rampart for a significant time, to the extent that the rock face of the rampart actually melts and forms a glassy or bubbled surface.  Craig Phadrig for example shows signs of intense heat vitrification along the entire 230m circumference of its interior rampart. Another example is Wincobank which has heat vitrification along its 430m rampart

Dating of Forts

Insert dating evidence Here.

Vitrified forts are notorious for their lack of strong dating evidence, recently however,

Materials available to burn

A number of excavations have unvieled the charred remains of wood used in the vitrification process, wood is known to burn at different temperatures, with Oak and Yew being the hottest available in the British Isles. An analysis of the wood remains will reveal the natural burning temperature of the wood, which coupled with details of the rock in question would indicate if the wood alone could have reached the correct temperature to perform vitrification.

A further factor is other materials used to help the vitrification process, these may include; salt has been suggested as capable of raising the temperature of the fire, some rocks may themselves give off minerals which could increase the temperature or act as a flux during vitrification. Furthermore there is evidence that some vitrified ramparts had an outer layer of smaller stones which became the outer vitrified layer. Presumably some additional material would have been required to ensure the smaller stones remained in contact with the rampart long enough for them to fuse.

Number of Ramparts/specific relationship between vitrified ramparts and others

Many vitrified forts have a double circular or oval rampart, with the inner vitrified. This may show them as having a cultural similarity and therefore allow us to tie together multiple forts to determine the spread of the culture.

Types of Rock used in Vitrification

Geographic Distribution

Analysis of the geographic distribution shows a marked trend towards a “Scottish homeland” for vitrified forts. With a few exceptions vitrified forts occur mainly in scotland, out of 260 hill forts in Scotland, 48 have been shown to have been classified as vitrified. Eslewhere in the british Isles vitrification is almost unknown. Even in Scotland vitrified forts tend focus to the north of the Forth.

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