A CLASSIC CASE OF CONFIRMATION BIAS
BILL SAUNDERS
The Origin of the Norfolk Broads - a classic case of Confirmation Bias
mallards
Born: Bombay,26th October,1882
Educated: Liverpool University, 1904-'07; Newnham College, Cambridge, 1910-'12
Botanist
Ecologist
Artist
"Philosophical Biologist"
Devotee of Byzantium, its history and Orthodox Christianity.
Died: Norwich, 13th August, 1963.
In 1935 Marietta Pallis received a considerable inheritance from her late father, the poet Alexandros Pallis, and purchased a small farm house with seventy six acres of peat grazing marsh at Long Gores, near to the ruins of Hickling Priory. She had known the site since she was an undergraduate, and had rented it since the end of the First World War for use as a summer residence, a place of study and research, and a base for her travels in Europe and the Middle East.
Two learned articles in respected scientific journals published in 1911 bear early witness to Marietta Pallis's talents as a botanist and ecologist, one on aquatic and fen formation in Broadland, the other a seminal analysis of the causes of water salinity around the upper reaches of the River Thurne. In 1916, she published the results of her researches into the floating fens of the Danube delta. A variety of Dog Violet local to the dunes between Waxham and Sea Palling was once known as Miss Pallis's violet, and a species of hairy-leafed ash tree was named Fraxinus Pallisiae in her honour.
She took up more permanent residence at Long Gores after the Second World War, and continued her interest in local botanical and ecological research.
Marietta Pallis also wanted a swimming pool.
From Mike Page's "A Broads-Eye View", Halsgrove, 2005
"If the pool encouraged scientific reflection, it was created for other purposes. Pallis had been a devoted swimmer, and in old age pursued a gentle private bohemianism, swimming naked in the marsh. Swimming pools do not, however, demand such intricate shape; the pool also formed a symbolic landscape. The Double-Headed Eagle Pool followed the 1952 publication of Pallis's Tableaux in Greek History, a homage to Byzantium expressing an unorthodox version of Greek myth, history and Orthodox Christianity, based in part on performed theatrical tableaux. Pallis was part of a wealthy Greek merchant family and considered herself Greek. In its symbolism the pool, marking the 500th anniversary of the 1453 fall of Constantinople, supplemented the tableaux in peat and water. Islands form a double-headed Byzantine eagle with imperial crown, the two-barred cross of the patriarch of Constantinople and the three-barred papal cross, and the Greek initials MP. The pool also quickly became a memorial space. Pallis's companion Phillis Clark died in 1955 in Cyprus, was initially buried in Kyrenia, but reinterred in 1959 on the island. Pallis was buried alongside in 1963."
"Experiments in landscape; the Norfolk excavations of Marietta Pallis." David Matless and Laura Cameron, Journal of Historical Geography, 2006.
The planning of the pool co-incided with the publication, in July 1953, of the text of Joyce Lambert's Presidential Address to the Norwich and Norfolk Naturalists' Society in which Lambert first made public the artificial origin of the Broads; a copy was sent to Marietta Pallis by a friend. Matless and Cameron relate that her inital reaction to Lambert's thesis was equivocal, althought she thought the work "very well done". However, she had become more convinced by the time the construction of the pool started in August, an event which produced something of a surprise:
"When I began digging the pool I had taken for granted that peat was permeable, now I do not think so. The impermeability of peat is quite sufficient for the extraction of pressure peat to a depth of eight to ten feet, and more, . . . . "
"The impermeability of peat and the origin of the broads" M.Pallis, Glasgow, 1956
Peat is remarkably resistant to water seeping through it, and the deeper you go, the more resistant it becomes because of the pressure of the ground above. Previously unknown to Pallis and Lambert, and therefore presumably also to the Department of Botany at Cambridge University, this characteristic of peat has been part of the lore of the construction industry, at least since the late 18th century (Tandy in litt.). It would have come as no surprise to the local men who dug the pool, nor to their forebears.
Pallis recognised the relevance of her discovery to Joyce Lambert's concept of man-made broads, and directed operations on the pool accordingly.
"I fell naturally into the medieval method - the obvious one - for extracting peat below the water-level, by digging pits, and isolating them from each other, leaving bars between to be cut later when re-uniting the waters." ibid.
It worked. Fired with enthusiasm, Marietta Pallis warmly invited Joyce Lambert to visit and see for herself.
"If you care to come one day, and the sooner the better, as I do not think I will be at it much longer. Do bring sandwiches [sic]. I leave the house before 8.30, so my friend, Mrs Clark, would bring you out, or if she is out, just follow the track and you will find us - it is easy". per Matless and Cameron, 2006
Joyce Lambert accepted the invitation early in September; Marietta Pallis followed up the visit with frequent progress reports, and wrote again in October about a retired engineer to the Catchment Board, who had spoken of his own experiences of peat impermeability.
Lambert, impressed by Pallis's discovery, corresponded with her about it, found other anecdotal evidence to confirm it, and incorporated it all, along with a description of the pool's creation, into the 1960 book (see under "How did they really do it?").
Why not? The probable answer is simple, and to nobody's discredit: what Pallis had shown Lambert was too little - the 'experiment' was on a very small scale and lacked formal research data - and too late; Lambert was moving that summer to Southampton, and her collaborator, J.N. Jennings, to Australia, both to take up new appointments; her theory had the support of her colleagues and of leading figures at Cambridge, including the hugely influential botanist, Harry Godwin, the eminence grise behind much of the broads research (and no friend of Marietta Pallis); further research to confirm her own theory was in train, with the promise of very low water levels from Charles Green. Wheels were in motion; the die was already cast.
In addition, there seem to have been failings in Pallis's advocacy of her own cause. In 1956 she wrote an article about the pool; this was in response to Charles Green's early disclosure of his researches at the Yarmouth power station, which had been published in The Times in May of that year (see under "How Joyce Lambert's theory developed"). Pallis was sceptical, and remained so, about such large changes in relative sea level.
"I think I can offer a simpler, more immediate explanation, which makes fluctuations of level redundant, even if they exist as Mr Green thinks." Pallis, 1956
She submitted the article to the editor (E.A.Ellis) of the "Transactions of the Norfolk and Norwich Naturalists Society"; unfortunately, she did not confine her thoughts simply to the pool's excavation.
"Ellis would seem to have suggested the excision of the later, more philosophical, less Norfolk-specific sections." Matless & Cameron, 2006
Pallis would not agree, withdrew the article, and had it printed privately with very limited circulation. Although the copy of this small pamphlet in the Millennium Library, Norwich, includes liberal notes and addenda, all apparently hand-written by the author, the content remains frustratingly lacking in details about the pool and the methods used to create it.
A few more details of the pool and its creation can be gleaned from Pallis's letters to Lambert, courtesy of Matless and Cameron.
". . . towards the end, we used all the Norfolk marsh tools . . . of which I have a complete collection . . . we used shore cutter, made from an old scythe tip, dydle, and long and short crooms, beside the knife recently made for me by the blacksmith . . . . There is no reason to suppose that any others were used in the cuttings of the 13th century - all adequate, no detestable modern contraptions."
Pallis to Lambert, 14th October, 1953
Again, this is not as revealing as it might have been. Ellis describes all these tools and their uses in an appendix to his 1965 book, but some names, like 'dydle' and 'croom' (or 'crome') are generic. If Pallis's collection was indeed complete, then it would have included a turf-spade (the Norfolk term for a 'becket'), and a 'scoop' or 'slubbing spade', which would have been useful for any bailing needed.
" . . .; thus the men often stood well below the surface of the marsh, and were throwing up to the full of their powers." (Pallis, 1956) does not make it clear what it was the men were throwing up; this was only revealed when Pallis published again in 1961 - it was water thrown up by "spade or bucket scoop-up", not peat.
This 1961 article was again to argue against Green. His evidence from the south Denes site consisted of a layer of two species of mollusc (acorn barnacles and dog whelks) which dwell exclusively between the high and low water marks on beaches; they were found, mixed up with broken thirteenth century pottery and mussel shells, at a depth in the beach some thirteen feet below the present mean sea level. Green, supported by Hutchinson and also by Jennings, had claimed this as proof of the level of the intertidal zone in the thirteenth century. Pallis refers scornfully to "Messrs. Green and Hutchinson's shellfish".
"This brings me to the question of the levels treated by Messrs. Green and Hutchinson, in connection with the archaeological and other finds, adduced as evidence for a lower sea level relative to the land at the time of the digging of the Broads; but they refer mainly to Yarmouth town itself, and for other reasons, I cannot believe - apart from the impermeability of peat - that the levels can have been such as to to affect the up-valley marshes, and the mussel and barnacle beds represent more than a fortuitous circumstance peculiar to the region; it seems more likely to be connected with the silting up of the Norfolk and Suffolk river-valleys by the tidal river-dominating North Sea . . . ."
"There are comings and goings, sinkings emergings, submergings at various depths, and for various lengths of time, shiftings, sweepings away, . . ."
"To sum up: I do not believe in Messrs. Green and Hutchinson's evidence as proof of subsidence and elevation." "The status of the fen and the origin of the broads", Pallis, Glasgow, 1961
Compare this with Martin George's (1992) report on similar excavations, carried out in the 1980s, to provide a new sea outfall for the Yarmouth sewers; a comparable layer of shells and pottery was found near the Haven Bridge at a depth of twenty feet below mean sea level, but most of the the pottery was from the fourteenth and fifteenth centuries.
"[The evidence] shows that the shells must have shifted, either as a result of human interference, or through wave or tidal action."
With the publication of Lambert's book in 1960, the whole focus of a very public debate was on a last ditch stand by proponents of natural origins, (who seem to have failed to use the obvious discrepancy between Lambert and Green on the subject of water levels as ammunition for their cause).
Man-made origins inevitably prevailed, and, although Pallis's prescient 1961 article did receive some authoritative support, it was Green's ideas, having achieved wide circulation in The Times and the 1960 book, which gained ascendancy.
"Lambert recalls visiting Long Gores in September 1953, seeing Pallis's paintings and discussing impermeability. While Pallis's earlier broads research had been Lambert's 'starting point' and 'bible', Pallis's later writings were a little 'odd'. Asked if she thought Pallis was still a serious scientist, Lambert said yes, but that there were other, by implication non-scientific elements in her late work: 'I think she was a serious scientist but with rather a shall we say airy fairy side to it', non-scientific elements which were to be taken 'with a pinch of salt'." Matless and Cameron, 2006
Aspects of Pallis's writings, and indeed of her persona, may have struck many people as 'odd', but as one reviewer observed, her "knowledge of the Broads is unrivalled".
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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