+------ | Irregular made ground | 5 | Clayey | | Alluvium 5 +------ | 4 | Peat | 9 +------ | | | | | 10-12 | Sand and Gravel | | | | | 21 +------ 2 | +------ Gravel 2 | 25 +------ | 4'6" | Running Sand | 29' 6" +------ Gault |
[Illustration: 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).
| _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" ======
[Illustration: 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.
_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.