The stratigraphic sequence in Sussex as drawn by Mantell in The Fossils of the South Downs, 1822. Were the rocks of the Weald [no. 7] a protrusion of older rocks to the surface or a recent deposit of younger rock?

he had correctly identified the Tilgate Beds as Secondary, he did admit that the precise 'geological position of these beds [within the Secondary series] is involved in much obscurity and cannot at present be satisfactorily determined'.

Faced with the disbelief of the Geological Society, shortly after this meeting Mantell made yet another survey of the Sussex rocks, this time with his friend Charles Lyell. Riding west from the Tilgate Forest, Lyell and Mantell searched for quarries that contained strata and fossils that matched those found at Whiteman's Green. They were hoping to find a site where the different layers of rock were clearly exposed in the geological sequence, so they could prove beyond doubt the exact position of the Tilgate Beds within the Secondary series of rocks. If they could convince the experts that the Tilgate rock was Secondary, then surely no one would doubt that Mantell had indeed found an ancient giant lizard?

To Mantell's delight, they uncovered similar organic remains -bones, teeth and 'numerous vegetables allied to the Cycas' - in the sandstone cliffs of Hastings, Rye and Winchelsea. Even better, in a quarry near Rye they found the strata laid bare. Sandstone and limestone matching the Tilgate beds were embedded in the Secondary rock known as Iron-sand.

After this expedition, on i June 1822 Mantell wrote triumphantly to Dr William Fitton, the Secretary of the Geological Society: 'I think we may fairly conclude that the sandstone of Rye, Winchelsea, Hastings, Tilgate Forest and Horsham are but different portions of the same series of deposits belonging to the "Iron-sand" formation.' Mantell was now completely satisfied that the limestone and sandstone in which he had found the giant bones in the Weald could be placed in the Secondary series, well below the chalk formations. Consequently, in his letter to the Geological Society he went even further. In defiance of the experts such as Buckland, he restated his own interpretation ol the animal remains that he had found. The large herbivorous teeth were now clearly identified as 'Teeth of an unknown Herbivorous Reptile, differing from any hitherto discovered either in a recent or tossil state'. In addition, he confirmed that he had the teeth and bones of a lizard resembling those found at Stonesfield, and 'Teeth and bones of crocodiles and other Saurian [lizard] animals of an enormous magnitude'. From the evidence of this letter the amateur Gideon Mantell was in no doubt that his beguiling view of a buried ancient world inhabited by several different species of giant reptiles herbivores and carnivores -was an accurate one.

However, his letter was regarded as of such insignificance by senior members of the Society that it was not even read out, as planned, to the eminent company. For one thing, George Bellas Greenough, a Fellow of the Royal Society, a former MP and the first Chairman and President of the Geological Society, was convinced that iron-sand was always a marine deposit. Since Mantell had reported some freshwater shells mixed in with the giant bones, Greenough insisted that the Tilgate beds could not be iron-sand and refused to change his opinion in the light of Mantell's findings.

William Buckland, too, was certain that the Weald rock resembled a recent, Tertiary rock he had seen while travelling in Italy and so was not a Secondary stratum. Consequently, in his view, Mantell's 'reptiles' had to be large mammals. And such was the standing of both Buckland and Greenough that other members could not accept that a provincial surgeon could possibly have knowledge that surpassed that of the Oxford and London men who were the leaders in the field.

Over six months elapsed before it was decided that Mantell's letter to Fitton on the strata of the Tilgate Forest would be read before the Geological Society. The minutes of the meeting on 17 January 1823 show that both Lyell and Mantell were present. At the Council committee meeting the following week, Mantell's paper was read and passed on to referees to check before publication. However, it remained unpublished for a further three years. The archives reveal that Gideon Mantell had considerable difficulty getting his papers published by the Society. One unsigned letter from a referee considering his paper on fossil vegetables wrote: 'the notice is not of sufficient importance to be printed'. George Greenough, too, turned down Mantell's paper on the Tilgate Forest. William Buckland was so convinced that Mantell was wrong, he wrote specifically to warn him against claiming that the teeth and bones were found in 'the older Iron-sand formation'. Mantell believed this advice came from the best of intentions and commented on 'the generous kindness that marked his character'.

Mantell's uphill struggle to get his ideas accepted by the experts was not unique. One amateur geologist, Robert Bakewell, who was not allowed to join the Geological Society although he wrote a popular book, Introduction to Geology, wrote frankly about the difficulties. 'There is a certain prejudice,' he said, 'among the members of the Scientific Societies in London and Paris, which makes them unwilling to believe that persons residing in provincial towns or the country can do anything important for science.' William Smith, the surveyor who pioneered studies of strata in England and was also not a member, once remarked: 'the theory of geology was in possession of one class of men [at the Geological Society] and the practice in another'. Gideon Mantell, an amateur from the provinces with none of the trappings of the upper classes, was very much an outsider. The disappointment he felt at the rejection of his ideas, and his failure to obtain recognition for his giant lizards, was recorded in his diary:

The past year, like its predecessors, has fleeted away almost imperceptibly, and I am as far from attaining that eminence in my profession to which I aspire as at the commencement of it. The publication of my work on the Geology of Sussex . . . has not yet procured me that introduction to the first circles . . . which I had been led to expect it would have done. In fact I perceive so many chances against my surmounting the prejudice which the humble situation of my family naturally excites in the mind of the great, that I have serious thoughts of trying my fortune in Brighton or London.

Since in the eyes of the experts at the Geological Society there was so much doubt about the stratigraphy of the Weald and this was crucial for interpreting the animal remains - the Secretary William Fitton came down from London to settle the matter once and for all. Fitton, unlike Mantell, was a veteran of two universities, having studied at both at Edinburgh and Cambridge. To add to his flawless academic pedigree, he was also a Fellow of the Royal Society. His good fortune had been assured when in i 820 he married 'a most amiable lady, who brought him the means of a comfortable existence'. So comfortable, in fact, that he was able to retire and devote himself to geological pursuits.

With Gideon Mantell providing much of the fossil evidence, Fitton started his investigations of the Weald in 1822. Since Mantell was invariably busy with his medical duties he was often unable to accompany the geologist on his forays around Sussex, but gradually Fitton began to make sense of the rocks of the Weald.

The first clue to the origin of the Weald strata came from the pronounced 'ripple marks' in the sandstone in the Tilgate Forest. These marks resembled the pattern of sand on a beach, as though countless shallow wavelets had moved across the soft strata. Mantell had already noted the 'extraordinary appearance' of this rock, 'being everywhere marked with undulating furrows, so strikingly resembling the impressions made on the sand . . . by the action of waves'. Dr Fitton speculated that the rocks might have been formed in a low-lying flood plain or along the edge of a lake or river delta, where sandbanks had accumulated.

A careful study of the shells embedded in the rock confirmed that the Tilgate beds were indeed part of a freshwater deposit. William Fitton took some of the shells to Paris to discuss them with invertebrate specialists such as Adolphe Brongniart, the son of the distinguished Alexandre Brongniart, the colleague of Cuvier. From the scanty impressions of the creatures Fitton was able to identify nine or ten species of univalves and bivalves. Some of these molluscs, such as the Unio valdenisis, a clam or pearl musselA could never have survived in salt-water. Fitton also realised that the Sussex marble embedded in the Weald clay, used for centuries to adorn the walls of Petworth Priory and other grand local houses, was formed from the shell of another freshwater creature: the Paludina snail. Gradually Fitton and Mantell became experts on freshwater shells such as Planorbis, Lymnia, Paludina and Cyrena. Fitton speculated that the freshwater deposits of the Weald could be explained if this region had once been a vast river delta.

But if the Tilgate beds were a freshwater deposit, how could they be part of the marine iron-sand in the Secondary series? It took Fitton several years to make sense of his data. Finally, he realised that the assumption made by Greenough and other senior members of the Geological Society that the iron-sand could only be marine was wrong. There were two types of iron-sand, one marine and the other freshwater. 'And now all things fell into their proper places,' Fitton wrote to a

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