Part 2

+---------- High water (12' 6" above O.D.) | 12' 6" | 12' 6" +---------- Ordnance Datum 4' 0" | Silt and clay 16' 6" +---------- {| {+---------- Low water (6' 0" below O.D.) {| {| 19' 6"{| {| {| {+---------- Bed of river (17' 6" below O.D.) {| 36' 0" +---------- | | | 9' 0" | Sand with shells | | | 45' 0" +---------- 3' 6" | Loam and sand 48' 6" +---------- | 5' 6" | Ballast with shells | 54' 0" +---------- 3' 6" | Loam with Peat 57' 6" +---------- 3' 6" | Fine red ballast | mixed with clay 61' 0" +---------- 5' 0" | Blue and grey clay | mixed with sand 66' 0" +---------- 1' 0" | Ballast 67' 0" +---------- | 4' 6" | Silty Sand 71' 6" +---------- | Ballast with flint 1' 6" | and stone 73' 0" +---------- | | | Stiff grey clay | |

Here again we see that the only peat is a bed between three and four feet in thickness of mixed loam and peat more than 40 feet below mean sea level.

From these sections it is clear that along the direct and more permanent outfall from Cambridge to the north, peat forms but a small part of the Fen Beds.

Peat is a substance of so much value as fuel, of such importance to the agriculturist, of such commercial value in what we may call its by-products, and of such scientific interest in the history of its formation and the remains which its antiseptic properties have preserved, that it has, as might be expected, a large literature of its own.

I have before me a list of more than 150 references to peat or to the Fens.

PEAT; TREES AND OTHER PLANTS; TARN PEAT AND HILL PEAT; BOG-OAK AND BOG-IRON.

When we turn aside into the areas cut off by spurs of gravel and islands of Jurassic rock, we find wide and deep masses of peat which has grown and been preserved from denudation in these embayed and isolated areas. Burwell Fen, for instance, protected on the north and west by the Cretaceous ridge of Wicken and the Jurassic ridge of Upware, furnishes most of the peat used in the surrounding district. If we travel about two miles to the north-west from the pit dug near the railway station (see Fig. 4, p. 11) over the hill on which Ely stands, we shall come to West Fen, where there is a great mass of peat which has grown in a basin now almost quite surrounded by Kimmeridge Clay. In this there is a great quantity of timber at a small depth from the surface. The tree trunks almost all lie with their root-end to the south-west, but some are broken off, some are uprooted, telling clearly a story of growth on the peat which had increased and swelled till the surface was lifted above the level of floods. Then some change--perhaps more rapid subsidence, perhaps changes in the outfalls--let in flood water, the roots rotted and a storm from the south-west, which was the most exposed side and the direction of the prevalent winds, laid them low. The frequent occurrence of large funguses, _Hypoxylon_, _Polyporus_, etc., points to conditions at times unfavourable to the healthy growth of timber.

It is worth noting when trying to read the story of the Fens as recorded by their fallen trees that in all forests we find now and then a few trees blown down together though the surrounding trees are left. This may be the result of a fierce eddy in the cycloidal path of the storm, but more commonly it seems to be due to the fact that every tree has its "play," like a fishing rod, and recurring gusts, not coinciding with its rhythm, sometimes catch it at a disadvantage and break or blow it down.

The story told by the West Fen trees is quite different from that told by the water-borne and water-worn trunks in the section by Ely station.

The same variable conditions prevailed also in the more westerly tracts of the Fen Basin, but the above examples are sufficient for our present purpose.

From the large numbers of trees found in some localities and from records referring to parts of the Fens as _forest_ it has sometimes been supposed that the Fens were well wooded, but forest did not generally and does not now always mean a wood, as for example in the case of the deer forests of Scotland.

When Ingulph[5] says that portions of the Fenland were disafforested by Henry I, Stephen, Henry II, and Richard, who gave permission to build upon the marshes, this probably meant that they no longer preserved them so strictly, but allowed people to build on the gravel banks and islands in them.

[5] _History of Croyland_, Bohn's edition, p. 282.

Dugdale, recording a stricter enforcement of game-laws, quotes proceedings against certain persons in Whittlesea, Thorney and Ramsey for having "wasted all the fen of Kynges-delfe of the alders, hassacks and rushes so that the King's deer could not harbour there." He does not mention forest trees.

In the growth and accidents of vegetation in a swamp there are some circumstances which are of importance to note with a view to the interpretation of the results observed in the Fens.

For instance in fine weather there is a constant lifting and floating of the confervoid algae which grow on the muddy bed of the stream. This is brought about by the development of gas under the sun's influence in the thick fibrous growth of the alga. The little bubbles give it a silvery gleam and by and by produce sufficient buoyancy in the mass to tear it out and make it rise to the surface dropping fine mud as it goes and thus making the water turbid. Other plants, such as Utricularia, Duckweed, etc., have their period of flotation, and in the "Breaking of the Mere" in Shropshire we have a similar phenomenon. In the "Floating Island" on Derwentwater the same sort of thing is seen with coarser plants. All these processes are going on in the meres and in the streams which meander through the Fens and did so more freely before their reclamation. But besides this, when the top of the spongy peat is raised above the water level and dries by evaporation, then heath, ferns and other plants and at last trees grow on it, until accident submerges it all again.

This at once shows why we often find an upper peat with a different group of plant remains resting upon a lower peat with plants that grow under water.

The most conspicuous examples of these various kinds of peat we see in the mountainous regions of the North and West, where the highest hills are often capped with peat from eight to ten feet in thickness, creeping over the brow and hanging on the steep mountain sides. Sometimes, close by, we see the gradual growth of peat from the margin of a tarn where only water-weeds can flourish.

The "Hill Peat" is made up of Sphagnum and other mosses and of ferns and heather.

The "Tarn Peat" of conferva, potamogeton, reeds, etc.

As Hill Peat now grows on the heights and steeps where no water can stand and Tarn Peat in lakes and ponds lying in the hollows of the mountains and moors, so the changes in the outfalls and the swelling and sinking of the peat have given us in the Fens, here the results of a dry surface with its heather and ferns and trees, and there products of water-weeds only, and, from the nature of the case, the subaerial growth is apt to be above the subaqueous.

One explanation of the growth of peat under both of these two very different geographical conditions is probably the absence of earthworms. The work of the earthworm is to drag down and destroy decaying vegetable matter and to cast the mineral soil on to the surface, but earthworms cannot live in water or in waterlogged land, and where there are no earthworms the decaying vegetation accumulates in layer after layer upon the surface, modified only by newer growths. Some years ago a great flood kept the land along the Bin Brook under water for several days and the earthworms were all killed, covering the paddock in front of St John's New Buildings in such numbers that when they began to decompose it was quite disagreeable to walk that way. It reminded me of the effects of storm on the cocklebeds at the mouth of the Medway, where the shells were washed out of the mud, the animals died on the shore and the empty shells were in time washed round the coast of Sheppey to the sheltered corner at Shellness. Here they lie some ten feet deep and are dug to furnish the material for London pathways.

In those cases when the storm had passed the earthworms and the cockles came again, but the Hill Peat is always full of water retained by the spongy Sphagnum and similar plants, and the Fens are or were continually, and in some places continuously, submerged and no earthworms could live under such conditions.

The blackness of peat and of bog-oak may be largely but certainly not wholly due to carbonaceous matter. Iron must play an important part. There is in the Sedgwick Museum part of the trunk of a Sussex oak which had grown over some iron railings and extended some eight inches or more beyond the outside of the part which was originally driven in to hold the rails. Mr Kett came upon the buried iron when sawing up the tree in his works and kindly gave it to me. From the iron a deep black stain has travelled with the sap along the grain, as if the iron of the rail and the tannin of the oak had combined to produce an ink. The well-known occurrence of bog-iron in peat strengthens this suggestion. An opportunity of observing this enveloping growth of wood round iron railings is offered in front of No. 1, Benet Place, Lensfield Road.

The trees in the Fens often lie at a small depth and when exposed to surface changes perish by splitting along the medullary rays.

It is not clear how long it takes to impart a peaty stain to bone, but we do find a difference between those which are undoubtedly very old and others which we have reason to believe may be more recent. Compare the almost black bones of the beaver, for instance, with the light brown bones of the otter in the two mounted skeletons in the Sedgwick Museum.

MARL.

"Marl," as commonly used, is Clay or Carbonate of Lime of a clayey texture or any mixture of these.

Beds of shell marl tell the same tale as the peat. Shells do not accumulate to any extent in the bed of a river. They are pounded up and decomposed or rolled along and buried where mud or gravel finds a resting place. Only sometimes, where things of small specific gravity are gathered in holes and embayed corners, a layer of freshwater shells may be seen.

But to produce a bed of pure shell marl the quantity of dead shells must be very large and the amount of sediment carried over the area very small, while the margin of the pond or mere in which the formation of such a bed is possible must have an abundant growth of confervoid algae and other water plants to furnish sustenance for the molluscs. Shell marl therefore suggests ponds and meres. Of course it must be borne in mind that in a region of hard water, such as is yielded in springs all along the outcrop of the chalk, there is often a considerable precipitation of carbonate of lime, especially where such plants as Chara help to collect it, as the Callothrix and Leptothrix help to throw down the Geyserite.

These beds of white marls, whether due to shells or to precipitation, are thus of great importance for our present enquiry as they throw light on the history of the Fens.

We should have few opportunities of examining the marl were it not for its value to the agriculturist. As it consists of clay and lime, it is not only a useful fertiliser but also helps to retain the dusty peat, which when dry and pulverised is easily blown away. Moreover, as the marl occurs at a small depth and often over large areas, it can commonly be obtained by trenching on the ground where it is most wanted.

THE WASH.

We have now carried our examination of the Fen Beds up to the sea, but to understand this interesting area we must cross the sea bank and see what is happening in the Wash. There is no peat being formed there, nor is there any quantity of drifted vegetable matter such as might form peat. There are marginal forest beds near Hunstanton and Holme, for instance, and it is not clear whether they point to submergence or to the former existence of sand dunes or shingle beaches sufficient to keep out the sea and allow the growth of trees below high water level behind the barrier, such as may be seen at Braunton Burrows, near Westward Ho, or at the mouth of the Somme. What is the most conspicuous character of the Wash is that the upland waters, now controlled as to their outlet, keep open the troughs and deeps while tidal action throws up a number of shifting banks of mud, sand and gravel, many of which are left dry at low water. Along the quieter marginal portions fine sediment is laid down, and relaid when storms have disturbed the surface. On these cockles and other estuarine molluscs thrive. Before the sea banks were constructed these tidal flats extended much further inland.

LITTLEPORT DISTRICT.

In the light of this evidence let us examine the Fen Beds east of Littleport, a district of great interest not only from its geographical position in relation to the Fens but also from the remains recently discovered there.

Looking north and west there is no high ground between us and the Wash. If we could sweep out the soft superficial deposits and abolish the sea banks the tide would still ebb and flow over the whole area.

If we look north and east we see the high ground stretching from Downham Market to Stoke Ferry and sweeping round to the south by Methwold and Feltwell and the islands of Hilgay and Southery, thus enclosing a great bay into which the Wissey on the north and the Brandon River on the south deliver the waters collected on the eastern chalk uplands.

The island known as Shippea Hill marks the trend of an ancient barrier blocking the northward course of the river Lark. (Fig. 6, p. 29.)

Here, then, it seems probable that we might find evidence of a local change from the conditions we now see in the Wash and those which have resulted in the formation of the Fens.

BUTTERY CLAY.

In deep trenching in the Fen between Littleport and Shippea Hill in order to obtain clay for laying on the peaty surface a very fine unctuous deposit was found at a depth of four or five feet. The overlying Fen Beds were chiefly peat with lenticular beds of white marl and grey clay, obviously laid down from time to time in small depressions in the surface of the peat. This marl was often largely made up of, or was at any rate full of, freshwater shells but sometimes showed evidence of having been gathered on the stems of Chara which on perishing have left small cylindrical hollows penetrating the partly consolidated marl. Under these beds of peat and marl there was the unctuous clay, which is sometimes referred to as the Buttery Clay. It is an estuarine deposit like that mentioned above as occurring in the Wash off Heacham, for instance. It contains shells of _Cardium edule_, _Tellina_ (_Tacoma_) _balthica_, _Scrobicularia piperata_, and other estuarine shells, some of which had the valves adherent or rather adjoining, for the ligament had perished. Mrs Luddington has in her collection the bones of the Urus, Wild Boar and Beaver, obtained from the peat above this Buttery Clay.

On the other or south-western side of Shippea Hill, which is an island of Kimmeridge Clay, we get further into the embayed and isolated portions of the Fen and we find more peat in proportion to the other deposits although it is very thin. There are still small lenticular beds of white marl similar to that nearer Littleport and the peat rests upon Buttery Clay of unknown thickness. In this part, however, no shells have yet been noticed. Near Shippea Hill the peat has recently been trenched with a view to obtaining clay with which to dress the surface of the peat and it was here, at a depth of four feet from the surface and four inches above the Buttery Clay, that the human bones described below (pp. 27-35) were found.

THE AGE OF THE FEN BEDS.

Now we may enquire what are the limits within which we may speculate as to the age of the Fen Beds.

These Turbiferous deposits all belong to one stage, though it may be one of long duration. They are sharply separated from the Areniferous deposits, i.e. the sands and gravels of the terraces and spurs which always pass under and, in fairly large sections, can always be clearly distinguished from the resorted layers at the base of the Fen Beds.

There is no definite chronological succession which will hold throughout the Fens. The variations observed are geographical--clay, marl, peat, etc., alternating in different order in different localities and subaerial, fluviatile, estuarine, and marine, having only a changing topographical significance.

The Fen Beds crept over an area where the underlying formation had been undergoing vicissitudes due to slow geographical changes--changes which, being at sea level and near the conflict of tides and upland water, produced irregular but often important results.

There is not in the Fens any _continuous_ record of what took place between the age in which the Little Downham Rhinoceros was buried in the gravel and that in which the Neolithic hunters poleaxed the Urus in the peat near Burwell.

PALAEONTOLOGY OF FENS.

Nor do we find any constant succession in the fauna and flora in the sections in the Fens any more than we find a uniform distribution of plants and animals over the surface to-day. The most numerous and largest specimens of the Urus I have obtained from near Isleham: the best preserved Beaver bones from Burwell. Modern changes of conditions have limited the district in which the fen fern (_Thelypteris_) or the swallow-tailed butterfly may now be seen; but nature in old times produced as great changes in local conditions as those now due to human agency.

When we compare the fauna of the Areniferous Series with that of the Turbiferous, although there is not an entire sweeping away of the older vertebrate and invertebrate forms of life and an introduction of newer, there is a marked change in the whole facies.

There is plenty of evidence about Cambridge of the gradual extermination of species still going on. Indeed, I feel inclined to say that there is no such thing as a Holocene age. I remember land shells being common of which it is difficult now to find live specimens, and my wife[6] has shown how the mollusca are being differentiated in isolated ponds left here and there along the ancient river courses above the town.

[6] "On the Mollusca of the Pleistocene Gravels in the neighbourhood of Cambridge," by Mrs McKenny Hughes. _Geol. Mag._ Decade 3, Vol. V, No. 5, May 1888, p. 193.

But we have not in older beds of the Turbiferous or newer beds of the Areniferous Series any suggestion of continuity between the two. There must have been between them an unrepresented period of considerable duration in which very important changes were brought about. Perhaps it was then that England became an island and unsuitable for most of the life of the Areniferous age.

Not only have we in the Turbiferous as compared with the Areniferous Series a change of facies but we have many "representative forms," a point to which that keen naturalist, Edward Forbes, always attached great importance.

We have for instance in the Fen Beds the Brown Bear (_Ursus arctos_) with his flat pig-like skull, instead of the Grizzly (_Ursus ferox_) of the Gravels with his broad skull and _front bombé_.

If we turn to the horned cattle we shall find a confirmation of the view that there was not an entire break between the Turbiferous and Areniferous fauna for the Urus (_Bos primigenius_) occurs in both. This species became extinct in Britain in the Turbiferous period and before the coming of the Romans, for no trace of it seems to have been found with Roman remains in this country; and indeed when we remember the numerous tribes, the dense population and high civilisation of the natives of Britain in Roman times it seems improbable that they can have tolerated such a formidable beast as this wild bull around their cultivated land.

Some confusion has arisen as to the description and the names of the Urus and the Bison. Caesar, who was not a big game hunter and probably never saw either, has given under the name Urus a description which evidently mixes up the characters of both. Both existed on the continent down to quite recent times and the Bison is still found in Poland, but later writers also have evidently confounded them. For instance, the Augsburg picture of the Urus is correct, but Herberstein's, which also is said to represent the Urus, is obviously that of a Bison. I have gone into this question more fully elsewhere[7].

[7] "The Evolution of the British Breeds of Cattle," _Journ. R. Agric. Soc._ Vol. V, Ser. 3, pp. 561-563, 1894. "On the more important Breeds of Cattle which have been recognised in the British Isles in successive periods, and their relation to other archaeological and historical discoveries," _Archaeologia_, Vol. V, Ser. 3, pp. 125-158, 1896. Cf. also Morse, E. W., "The Ancestry of domesticated Cattle," _Twenty-seventh Annual Report of the Bureau of Animal Industry_, 1910, Department of Agriculture, U.S.A.

The Urus (_Bos primigenius_) is common in the Fen Beds and is of special importance for our present enquiry, as there is in the Sedgwick Museum a skull of this species found in Burwell Fen with a Neolithic flint implement sticking in it. The implement is thin, nearly parallel sided, rough dressed, except on the front edge which is ground, and it is made of the black south-country flint. It is very different in every respect from the thick bulging implements with curved outlines, which being made of the mottled grey north-country flint or of felstone or greenstone suggest importation from a different and probably more northerly source.

This gives us a useful synchronism of peat, a Neolithic implement of a special well-marked type, and the Urus.

The Bison is the characteristic ox of the Gravels and never occurs in the Fen Beds; while the Urus, as I have pointed out above, occurs in both the Turbiferous and Areniferous deposits.