Part 4

Lower down the river near Ely a most important and interesting section has recently been exposed. A new bridge was built over the Ouse near the railway station and to obtain material for easing the gradient up to the bridge a pit was sunk close to it on the east side of the river, and was carried down to the Kimmeridge Clay thus giving a clear section through the whole of the alluvium (Fig. 4, p. 11).

Depth

| a | | +------ 4' | b | +------ 7' | c | +------ 10' d | +------ 12' 6" e | +------ 13' 2" | | | f | | | | +------ 21' 2" g | +------ 23' 2" h | |

a. Dark clay, with much carbonaceous matter, scattered stones, and freshwater shells 4' 0" b. Tough clay 3' 0" c. Dark clay full of bits of wood 3' 0" d. Light coloured clay full of rootlets 2' 6" e. Rusty sand 8" f. False bedded gravel and sand pierced by rootlets 8' 0" g. Black silt and gravel 2' 0" ------ h. Gault 23' 2" ======

It will be noticed that there is very little peat here and all of it was below O.D. The upper four feet of the clayey peat (f) looked as if the vegetable matter had been transported, perhaps from peat beds being destroyed by the river higher up, and been carried down in flood with the clay, while the lower four feet of peat (h) was only a cleaner sample of the same, before the river had cut down into the clay. The trees in both f and h were not trees that had grown on the spot and had been blown down, but were broken, water-worn, and evidently transported.

a +----------------- b +----------------- c +----------------- d +----------------- e +----------------- | f |················· g | +----------------- | h | | +----------(1)---- i | +----------------- | j | | +----------(2)----

a. Surface soil 7" b. Clayey alluvium 7" c. Peaty alluvium 9" d. Brown clayey alluvium 1' 6" e. Peaty alluvium. 9" f. Brown clayey peat with trees scattered throughout g. and lenticular beds of freshwater shells in it 4' h. Peat with trees to 2' diam. 4' i. Mottled green and grey clay with lines of sand and gravel giving out water 2' j. Yellow clay with springs and much rusty water at bottom. 4' ------ 18' 2" ====== (1) Skull and a few other bones of horse. (2) Broken fragments of bone.

Scale 8' to 1"

If now we travel about 30 miles a little west of north we shall arrive near the shore of the Wash about half way across its southern coast line at Sutton Bridge. Here I had an opportunity of seeing the material of which the alluvium is composed. With a view to securing a sound base for the foundation of the piers of the Midland and Great Northern Railway bridge an excavation was made through the whole of the Fen Beds down to the Boulder Clay which as I have already stated was reached at a depth of 73 feet. The clerk of the works kindly gave me the following measurements (Fig. 5).

Depth Thickness

+---------- 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 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.

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.