A CLASSIC CASE OF CONFIRMATION BIAS
BILL SAUNDERS
The Origin of the Norfolk Broads - a classic case of Confirmation Bias
mallards
In "The origin of the Broads", (RGS Research Memoir No.2, 1952), Lambert's colleague, the geomorphologist J.N. Jennings, had dismissed the idea of their being man-made, largely on practical grounds. One of the seemingly powerful objections he raised was this: even assuming that people in times past could have dug peat from such depths in these marshy fens (which anyway, he argued, would have been impossible), why would they have gone to the trouble of doing so, when there was plenty of peat lying around on the surface which was much more readily accessible?
When Joyce Lambert was planning a final publication aimed at placing the true, artificial origin of the broads beyond doubt, she wanted to include a rebuttal for any rational 'counter arguments'. Although assistance from other academic disciplines was sought to deal with some unresolved matters, such as how and when the broads had been created, Lambert and Jennings together felt that they had already found the answer to this particular objection for themselves.
"The last of the former counter arguments to be disposed of concerns the reason for such deep excavations when large areas of surface peat were available which presumably could have been dug with much less difficulty and effort. The answer probably lies, at least in part, in the better combustible quality of the peat at the lower levels. Whereas the upper deposits consist predominantly of fairly fresh remains of reed and sedge, at the lower levels the compact, humified brushwood and fen peats were uncovered, and the latter may well have provided economic returns well worth the extra effort in extraction." Lambert and Jennings, 1960
The deep, denser brushwood peat burns longer and hotter than the peat on the surface.
Had the whole matter, untrammelled by this plausible opinion from a botanist and a geomorphologist, been considered initially in the light of the historical evidence that was available, there can be little doubt that they would all have arrived at a very different conclusion. The presumption that "large areas of surface peat were available which . . . . could have been dug with much less difficulty and effort" is incorrect. Certainly there were large areas of peat fen outside the designated turbaries, but it is equally certain that they were not available for use as fuel.
Both Dr.Martin George ("The Land Use, Ecology and Conservation of Broadland", Packard, 1992) and Dr. (later Professor) Tom Williamson ("The Norfolk Broads - A landscape history", MUP, 1997) emphasise a fact of which Lambert and Jennings were actually already aware:
"In other parts, landholders may have wished to retain substantial fenland areas undug in order to put them to the many other purposes such land served in earlier times other than merely providing turves." ibid.
These turbaries themselves were divided up. Some areas were retained for the direct beneficial use of a manor itself, others were parcelled out to tenants living on the manorial estate.
"One way of ensuring fair distribution of resources was through 'doling', by which specific areas of the common land were allotted to particular individuals . . . . By the end of the medieval period the majority of the wet fens appear to have been doled in this way, . . . . . Doles were not only mown, they were also cut for peat." Williamson, 1999
These doles were assets which could be passed down by inheritance from generation to generation, becoming divided and subdivided in the process. If you had no share of a turbary or wanted more, the only way you could get it was to buy it, rent it, or inherit it from somebody else.
Now ask yourself: "Why did they bother to dig so deep?"
They did it, of course, in order to extract as much valuable peat as they possibly could from their own limited area of turbary. They would have used every method available to them in order to do this.
"The remarkably constant level of the floors of the basins at between 3 and 4 metres from the present fenland surface is sufficient in itself to suggest that beyond this depth conditions generally became too difficult for further excavation, although good peat deposits could still be found."
Lambert and Jennings, 1960
There was a practical limit to the depth from which peat could be dug. The level bottoms of the basins show that they were always dug down to that limit.
When Clifford Smith found evidence in fourteenth century account rolls of peat being dredged up in bulk from underwater and then shaped into individual turves, he reasoned that this hitherto unknown practice was newly invented, and that its purpose, following Lambert and Jennings, must have been to maintain supplies of the deep, brushwood peat, when flooding of a formerly dry pit had made it impossible to dig it up with a turf-spade.
Martin George (1992) follows in turn:
"It seems highly likely that this method of winning peat . . . . was practised in Broadland once the diggings had become flooded, and there was a continuing demand for good quality fuel. However, it would have been a more laborious technique than direct digging, and in the deeper sites would only have been practicable round the margins of the workings, or along the baulks left between them [my italics]."
While peat of "unconsoldated, fluid almost" (Pallis, 1961) consistency may have been scraped from the bottom in the few, shallower sites,
What were these other methods and how did they work? Smith's interpretation was aided by a group of fifteenth century records from Bartonbury Hall. Despite the very limited information, he was able to deduce a picture which was, in many respects, to prove remarkably accurate.
Peat was recovered in bulk 'with a dyday', 'with laggying', or 'with a shovel'. A 'dyday' or 'dyda' must have been an implement from the family of traditional Broadland marsh tools known as 'dydles' or 'didles', used for dredging mud and weeds from dykes and river channels. The medieval version probably took the form of a long-handled "scraper with bag-net attached" ("The Broads", E.A.Ellis, Collins, 1965).
In later researches, Smith found detailed evidence of a similar practice in Holland, where an identical tool was known as a baggerbeugel:
"The men who dredged the peat, or trekkers, also used straps around the waist and attached to the baggerbeugel, in order to exert more pressure upon it. The peat was then brought to the balk, or leggaker,on which a thick layer of reeds was spread. The peat was then raked, mixed with water, and 'mashed' wirh an iron claw to form a homogeneous mass. This was spread to a depth of 40 centimetres and allowed to drain. The peat was then pressed by means of boards attached to the men's feet. After repeated treadings the surface of the compressed peat is then scored, so that at a later stage during the drying process the peat shrinks and tends to ceack along these lines. The turves were then cut with a long and sharp spade." C.T.Smith, Geogr. J. 132(1), 1966
It was evident to Smith that there would have been a limit to the depth of water in which peat could have been dredged from the bottom of a flooded pit. The use of leather straps in Holland (where the peat diggings were quite shallow) confirms the principle that the longer the pole, the greater the leverage needed to scrape and lift wet material on the end of it.
"Barton Broad is now no more than six feet deep in many places from water level to the floor of brushwood peat, so that dredging of it for turf in the fifteenth century may not have been impossible, and there were, in addition, the standing balks which marked old property divisions [my italics] . . ." Smith, 1960
Aware of a rise in water levels since the fifteenth century, Smith clearly had in mind a limit of significantly less than six feet. Three to four feet was regarded as the limit when dydles were used for dredging dykes in the nineteenth century (vid. Ellis, 1966).
The non-consecutive series of fifteenth century records which has survived from Bartonbury Hall reveals that no turves were dug or cut; the activity consisted exclusively of the extraction of peat in bulk 'with a dyday', 'with laggying', or in one case 'with a shovel'. The references to the dyday and to "the several pond-water of the lord" show that water is involved, although boats are not specifically mentioned.
In contrast to the earlier last (or load) of 10,000 turves, a last of fen here was only enough bulk peat to make approximately 1,150 turves (perhaps 1000 with a bit over for good measure). Presumably all of it was then 'sold to the lord's men' or to others for D.I.Y. turf making.
Source: Smith, 1960
Note * Turves written, but crossed out and replaced by fen. ** Dyday written, but crossed out and replaced by laggying. 10d.[9d.]: the first figure is mine and correctly calculated, the figure in brackets is Smith's.
Smith assumed that 'laggying' was "a dragging or dredging operation", and concludes from these records:
"There is a very strong presumption that Barton Broad was already in existence in the fifteenth century. The existence of parcels of 'several pond-water' points to its existence, and so does the evidence of fisheries which belonged to Bartonbury Hall."
The evidence surely points to rather more than just the flooding of a big, formerly dry pit. These 'parcels' are in the lord's demesne turbary, and are therefore not related to doles. Short of drawing a picture, it is difficult to think of a more concise way of describing small, adjacent flooded peat diggings than with the expression "several pond-water".
What happened to them? They were turned into larger expanses of open water, the large sections known to have existed on Barton Broad.
"It is known that Barton Broad was divided into separate parcels of fishing rights in the 1560's." (ibid.).
One belonging to Bartonbury Hall was called Seyveswater, and another, Buryhallwater, ". . . which is well stocked with proberells, temges and eles which are plentifully taken and is very well replenished with wylde fowl." (ibid.). These fisheries would not have been much good unless they were quite big, and had physical boundaries to prevent the proberells and temges from swimming from one to another.
" . . . and by the sixteenth century Simon Toybe was paying 12d. rent for three acres of fishing in Barton Broad."
Williamson, 1999
How would anybody have tackled the task of removing the walls or balks of peat which separated the 'several pondwater'? They would have dug or hacked away the tops of the walls as best they could, perhaps with a shovel, perhaps with a tool especially designed for the purpose, and would then have used dydays to dredge up the rest from under water.
A 'laggying' implement may have been a tool similar to a mattock (c.f. 'lagomorph', any creature with an upper jaw shaped like a hare) used to chip or nibble away at the surface peat, and draw it back into a boat. All the valuable bulk peat, which would otherwise have gone to waste, would have been shaped into turves and used as fuel. That the acquisition of peat in bulk was not an exclusively amphibious operation is confirmed by a 1305 entry in the Martham records which reveals 'carriage' rather than 'ferrying' of fen.
Copyright 2009 The Medieval Making of the Norfolk Broads. All rights reserved.
The Origin of the Norfolk Broads - a classic case of Confirmation Bias
mallards