Elephant and Rhinoceros occurred in the older Fen Beds. It is true that they have been found under peat in the Fenland, but that is only where the gravel spurs of the Old Alluvial Terraces or Areniferous Series have passed under the newer Fen Beds.

I saw the remains of Rhinoceros tichorhinus in the gravel beds belonging to the older or Areniferous Series at Little Downham, and from the base of the gravel in the Whittlesea brickpit I obtained a fine lower molar of Elephas antiquus. This was, however, not in the Gravel, but squeezed into the soft surface of the underlying Jurassic Clay.

There have never been any remains of Elephant or Rhinoceros found in the Turbiferous series.

  Absence of Peat in Areniferous Series.

It is not easy to realise what the conditions were during the formation of the later Terrace Gravels (Barnwell type), and, if it is a fact, why there was not then, as in later times, a marshy peat-bearing area here and there between the torrential deposits of the upper streams near the foot of the hills and the region where the tide met the upland waters. A few plants have been found in the Barnwell gravel but they are very rare in this series. The older Terrace Gravel (Barrington type) might be expected to furnish evidence of the existence of abundant vegetation if we are right in assigning it to about the age of the peaty deposits overlying the Weybourn Crag. But at present we have no evidence of any such deposit in the Cambridge gravels.

Although there are great masses of vegetable matter formed in the swamps of tropical regions, peat is essentially a product of northern climes. Pliny[4] evidently refers to peat as used in Friesland but not as a thing with which he was familiar.

  Fen Beds not all Peat.

It must not, however, be imagined that the Fen Beds consist wholly or even chiefly of peat. As we travel north from Cambridge the surface of the alluvium is brown earth for miles and only here and there shows the black surface of peat. The numerous ditches for draining the land confirm this observation, and when we have the opportunity of examining excavations carried down to great depths into the alluvium we usually find only a little peat on the surface or in thin beds alternating with silt and clay and marl. Sometimes, but only sometimes, we have evidence of the growth of peat for a long time, then of the incoming of turbid water leaving beds of clay, then again of the tranquil growth of peat. All this points to changes of local conditions and shifting channels during a gradual sinking of the area, for some of the peat is below sea level.

I believe that the volume of clay is much greater than that of peat, although from the common occurrence of peat on the surface and clay in the depth the area over which peat is seen is greater. We have not, however, the data for estimating the proportion of each.

In embayed corners along the river even above Cambridge we find little patches of peat, while on the other hand in deep excavations near the middle of the valley we find only thin streaks of peat or peaty silt. In the trial boreholes at the Backs of the Colleges there was only this kind of record of former swamp vegetation.

  Sections in Alluvium.

In digging the foundations for the chimney of the Electric Lighting Works opposite Magdalene College the following section was seen (Fig. 1, p. 8).

Under the new Tennis Courts in Park Parade facing Mid-summer Common the section was somewhat different (Fig. 2, p. 9).

While in the pit dug some years ago by Mr Bullock at the other end of the Parade at the lower end of Portugal Place in the south-east corner of the Common there was a section very similar to the last (Fig. 3, p. 10).

Fig. 1. Section seen in foundations of chimney for Electric Lighting Works near river opposite Magdalene College, July, 1892.

These three sections, immediately north of Cambridge where the valley of the Cam opens out on to the Fens, are important as showing the variations right across the alluvium from side to side and the absence, here at any rate, of any indication of a constant sequence distinctly pointing to important geographical changes. A section seen under Pembroke College Boat House gave 16 feet of clay and peaty silt on the black gravel which here, as in the borings at the Backs of the Colleges, forms the base of the alluvium. About half way down were bones of horse and stag, but I do not believe that these are of any great antiquity, probably not earlier than mediaeval.

Fig. 2. Section seen in digging foundations of Tennis Courts on Midsummer Common, Cambridge.

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).

Fig. 3. Section seen in Bullock's Pit in S.E. corner of Midsummer Common.

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.

Fig. 4. Section seen in pit dug for material for making up the roadway east of the new bridge over the Ouse by the railway station. Ely, 1910.

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).

Fig. 5. Section seen at Sutton Bridge.

Here